Electric Ship Research and Development Consortium

Documents Collection

This site hosts MIT's portion of the ESRDC Consortium's technical papers and presentations. Please contact Professor Chrys Chryssostomidis if you are an ESRDC member for access to forms and report templates.

ESRDC members may access the internal Consortium document collection at https://www.esrdc.com/drupal-5.2/.

ESRDC Technical Reports to the Office of Naval Research are available at http://www.esrdc.com/onr.report.index.html

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A Collaborative Early-Stage Ship Design Environment

2012

Julie Chalfant, Blake Langland, Sherif Abdelwahed, Chryssostomos Chryssostomidis, Roger Dougal, Abhishek Dubey, Touria E. Mezyani, John Herbst, Thomas M. Kiehne, Juan Ordonez
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Recent advances in sensor and weapons systems are significantly increasing the electrical power that is required and the thermal loads that must be dissipated onboard US Navy ships. Thus, design tools and methods must bring detailed consideration of all disciplines early in the design process, including electrical, thermal and controls in addition to the traditional naval architecture and marine engineering. Effective interface of the multiple disciplines demands a collaborative design process. The Electric Ship Research and Development Consortium (ESRDC) has developed the backbone structure of a collaborative design environment with the goal of bringing together many disciplines early in the ship design process. This design environment brings many innovations, especially in the arena of simultaneous collaborative design. This paper describes the Smart Ship System Design (S3D) environment as developed to date, along with overall and discipline-specific visions of implementation of the environment in ship design.

Integrated Simulation Framework for Crash Back Operation

2012

Stefano Brizzolara, Pradya Prempraneerach, George Em Karniadakis, Chryssostomos Chryssostomidis
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We formulate a modeling and simulation framework that integrates models of an all-electric ship (AES) with ship and propeller hydrodynamic models. In particular we present the first simulation study about the transient behavior of the propulsion system of AES during crash stop and backing maneuvers. A time domain model of all electric propulsion system of a notional destroyer has been coupled with a simplified transient model of the hull and propeller hydrodynamics. The integrated power system of the integrated power system (IPS) includes all main elements of the chain, i.e. from power generators to control units down to frequency controlled electric motors. The simplified unsteady hydrodynamic model of the hull and twin shaft lines with fixed pitch propellers is based on semi-empirical quasi static data corrected with complimentary CFD simulations. The transient behavior of the electrical power distribution and motor control are analyzed and the relevant implications that these kind of violent transient maneuvers have on the engineering of the main electrical components are outlined in the paper.

Development of an Early Stage Ship Design Tool for Rapid Modeling in Paramarine

2011

Eric Thurkins
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In early stage ship design, it is often helpful to the designer to perform preliminary design and analysis on many configurations to assist in developing and narrowing the trade space. However, this fleshing out of diverse ideas can be time and resource consuming. A novel interface is proposed with which a designer can rapidly develop and alter basic, major design components from a ship from a compiled database of components and gain a rendered model for analysis within the naval design tool Paramarine.

Hierarchical Approach to Modular Machinery Arrangements in Early Stage Naval Electric Ship Design

2011

David Jurkiewicz
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The focus of this research is to develop a hierarchical structure that produces "families" of IPS modules and their required auxiliary equipment in response to user impact of desired power requirements. This forms the basis of an IPS machinery arrangement and design tool for early stage naval electric ship design.

Comparison of Turbulence Models for Simulating Flow in Waterjets

2011

Xian Luo, Brenden Epps, Chryssostomos Chryssostomidis, George Em Karniadakis,
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We have developed a fast numerical algorithm for simulating flows in complex moving domains. The new hybrid smoothed profile/spectral element method exhibits high-order accuracy as well as great computational efficiency as it removes the tyranny of mesh generation. Here we extend this work by incorporating a variational multiscale large eddy formulation for modeling the subgrid turbulent scales. We present verificiation and validation studies of the combined method and compare different turbulence modeling methodologies. Subsequently, we apply it to study laminar, transitional and turbulent flows in an axial-flow waterjet propulsion system (ONR AxWj-1). The robustness and efficiency of our methods enable parametric studies of many cases, which may aid greatly in the early stages of design and evaluation of such propulsion systems.

Simulation of a DC to DC Power Conversion Module for the All-Electric Ship

2011

Weston L. Gray, James L. Kirtley, Julie Chalfant, Chryssostomos Chryssostomidis
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The design of electric ships requires a tool to evaluate the relative merits of different electrical power distribution configurations; the MIT end-to-end simulator is just such a tool. This paper models one module to be used in conjunction with the end-to-end simulator: a power converter that converts MVDC bus voltage to 1kV DC. First, the power converter was designed to use commercially available technology. This design resulted in a low-frequency, 2 kHz, 200 kW power converter commonly called a double-ended, isolated forward converter. The initial converter design was then modeled in Simulink. The response characteristics of the converter were analyzed to ensure the response followed demonstrated behavior consistent with this type of converter. Finally, the model was tested against a nominal set of specifications that determined adequate response characteristics.

ESRDC Ship Notional Baseline Medium Voltage Direct Current (MVDC) Architecture Thermal Simulation and Visualization

2011

J. V.C. Vargas, J. A. Souza, R. Hovsapian, J. C. Ordonez, T. Chiocchio, J. Chalfant, Chryssostomos Chryssostomidis
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This work presents a fast visualization and thermal simulation tool developed as part of the Electric Ship Research and Development Consortium (ESRDC) funded by the Office of Naval Research (ONR) that is capable of providing quick responses during early stages of ship design. The tool allows for the visualization of thermal and electrical loads, and equipment locations and other variables of interest in the all-electric ship, proceeding to the computation of the resulting whole ship temperature and relative humidity distribution. For that, a previously developed simplified physical model [1-3] – which combines principles of classical thermodynamics and heat transfer, resulting in a system of three-dimensional differential equations which are discretized in space using a three-dimensional cell centered finite volume scheme – is enhanced to include fresh and sea water cooled systems throughout the ship. Therefore, the combination of the proposed simplified physical model with the adopted finite volume scheme for the numerical discretization of the differential equations is called a volume element model (VEM). A 3D simulation is performed in order to determine the temperature distribution inside the ship for the baseline Medium Voltage Direct Current (MVDC) architecture, and representative operating conditions are analyzed. Visit visualization tool [4] is used to plot the results.

A Design for the Interface Between a Battery Storage and Charging Unit, and a Medium Voltage DC (MVDC) Bus, as Part of an Integrated Propulsion System (IPS) in the All Electric Ship (AES)

2011

Thomas Trapp, Pradya Prempraneerach, Chryssostomos Chryssostomidis, James L. Kirtley, George Em Karniadakis
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In this paper we present the design of a rechargeable battery storage device for use in an all-electric ship. The purpose of this device is to provide power of predictable quality to selected equipment. In addition a recharging unit is proposed for recharging the battery from the ship’s electric bus.

Dual-Operating-Point Blade Optimization for High-Speed Propellers

2011

Brenden Epps, Oscar Viquez, Chryssostomos Chryssostomidis
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Propeller blade design for fast ships is often driven by cavitation constraints. A tradeoff exists, where larger chord lengths and section thicknesses typically improve cavitation performance but result in lower efficiency. Typically, chord lengths are optimized for the design condition (ship endurance speed), with some specified margin to prevent cavitation off-design (at maximum ship speed). Cavitation performance at the maximum speed is considered post-facto, and blade shape often needs to be modified for cavitation considerations in high-speed operation. This paper presents an improved method for blade shape optimization. The present method simultaneously considers the cavitation performance at the endurance speed design point and a maximum speed off-design point, and blade chord lengths and thicknesses are set to prevent cavitation at both operational conditions. During the present design optimization routine, the on-design load distribution is optimized, and the off-design performance is determined, such that the chord lengths can be set to a minimum that still prevents cavitation at both the on-and off-design conditions. A case study is presented, considering the notional design of a propeller for the U.S. Navy DDG51 destroyer-class ship. Propellers designed using standard chord/thickness optimization procedures are compared to those designed using the present procedures. Cavitation performance is compared for the two design methods.

Integration of the ESRDC Notional All-Electric Ship Visualization with Paramarine (PowerPoint Presentation)

2011

J. Chalfant, J. Souza, S. Motiwalla, C. Chryssostomidis, R. Hovsapian, J. Vargas, J. C. Ordonez
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Presentation related to paper entitled, "Analysis of Various All-Electric-Ship Electrical Distribution System Topologies. As advances in technology mature, the need is evident for a coherent simulation of the total electric-drive ship to model the effect of new systems on the overall performance of the vessel. Our laboratory has been developing an integrated architectural model in a physics-based environment which analyzes ship variants using a standard set of metrics, including weight, volume, fuel usage and survivability. This paper discusses advances in the model including the use of operational scenarios, incorporation of a survivability metric, and streamlining the performance of model. The model is employed herein to compare two possible distribution system topologies: a ring bus and a breaker-and-a-half. The ring bus is heavier and larger but more survivable. Fuel usage is equivalent in the two variants.

Presentation of A Design for the Interface Between a Battery Storage and Charging Unit, and a Medium Voltage DC (MVDC) Bus, as Part of an Integrated Propulsion System (IPS) in the All Electric Ship (AES)

2011

Thomas Trapp, Chryssostomos Chryssostomidis, George Em Karniadakis, Pradya Prempraneerach, James Kirtley
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In this presentation, we present the design of a rechargeable battery storage device for use in an all-electric ship. The purpose of this device is to provide power of predictable quality to selected equipment. In addition a recharging unit is proposed for recharging the battery from the ship’s electric bus.

Presentation of "All-Electric Ship" Model Power Conversion Module (PCM)

2011

Weston Gray, James Kirtley, Julie Chalfant, Chryssostomos Chryssostomidis
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The requirements, design, testing, and naval architecture parameters of the all-electric ship model are presented.

Video Transmission Over an In-Air Acoustic Link

2011

Rameez Ahmed, Laura Dubreuil Vall, Ranga Narayanaswami, Milica Stojanovic
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In this paper, we present the development of an in-air acoustic test-bed for rapid proof-of-concept testing of (underwater) communication technologies. In addition to more accurately representing the actual channel when compared to simulation, the test-bed also provides an easy method to introduce channel impairments, such as Doppler distortion, a controlled manner. This can be advantageous when the experiments need to be reproduced at a later time. We present the testing of video transmission over an acoustic channel using this test-bed. We utilize MPEG-4 video compression as it has efficient low bit rate compression capabilities. OFDM is chosen as the modulation technique as it provides robust high speed acoustic communication over underwater channels which are characterized by frequency selectivity and Doppler distortion.

MOOS-IvP Autonomy Tools Users Manual Release 4.2.1

2011

Michael R. Benjamin
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This document describes 19 MOOS-IvP autonomy tools. uHelmScope provides a run-time scoping window into the state of an active IvP Helm executing its mission. pMarineViewer is a geo-based GUI tool for rendering marine vehicles and geometric data in their operational area. uXMS is a terminal based tool for scoping on a MOOSDB process. uTermCommand is a terminal based tool for poking a MOOSDB with a set of MOOS file pre-defined variable-value pairs selectable with aliases from the command-line. pEchoVar provides a way of echoing a post to one MOOS variable with a new post having the same value to a different variable. uProcessWatch monitors the presence or absence of a set of MOOS processes and summarizes the collective status in a single MOOS variable. uPokeDB provides a way of poking the MOOSDB from the command line with one or more variable-value pairs without any pre-existing configuration of a MOOS file. uTimerScript will execute a pre-defined timed pausable script of poking variable-value pairs to a MOOSDB. pNodeReporter summarizes a platforms critical information into a single node report string for sharing beyond the vehicle. BasicContactMgr provides a basic contact management service with the ability to generate range-dependent configurable alerts. uSimMarine provides a simple marine vehicle simulator. uSimBeaconRange and uSim- ContactRange provide further simulation for range-only sensors. The Alog Toolbox is a set of offline tools for analyzing and manipulating log files in the .alog format.

Overview of MOOS-IvP and a Users Guide to the IvP Helm - Release 4.2.1

2011

Michael R. Benjamin, Henrik Schmidt, Paul Newman, John Leonard
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This document describes the IvP Helm - an Open Source behavior-based autonomy application for unmanned vehicles. IvP is short for interval programming - a technique for representing and solving multi-objective optimizations problems. Behaviors in the IvP Helm are reconciled using multi-objective optimization when in competition with each other for influence of the vehicle. The IvP Helm is written as a MOOS application where MOOS is a set of Open Source publish-subscribe autonomy middleware tools. This document describes the configuration and use of the IvP Helm, provides examples of simple missions and information on how to download and build the software from the MOOS-IvP server at www.moos-ivp.org.

Hydrodynamic Design of a Family of Hybrid SWATH Unmanned Surface Vehicles

2011

Stefano Brizzolara, Marco Bovio, Alessandro Federici, Giuliano Vernengo
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This paper presents the concept designs of two autonomous marine vehicles belonging to a new family of unconventional SWATHs optimized for low resistance at high speeds. The focus is concentrated on the prediction of the hydrodynamic characteristics and the optimization methods used to design the hull forms in order to minimize the propulsion power at the operational speed of the vehicles. For both vessels a modern automatic parametric optimization computer based procedure has been developed and RANSE calculations performed to validate the final design. The second vessel, is a hybrid SWATH, capable of reaching a top speed of 120 knots in the foil-born mode, at which four supercavitating hydrofoils are folded down into water. Main issues related to the design of surface piercing super-cavitating hydrofoils, for operation at such a high speed, are presented and discussed on the basis of the results obtained through CFD simulations and feedback from preliminary results of model tests in cavitation tunnel.

Sea-Basing: T-Craft Dynamic Analysis

2011

Chryssostomos Chryssostomidis
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Technical Objectives: The future T-Craft for sea-basing operations will be propelled by waterjets in Surface Effect Ship (SES) mode and will be subject to large seakeeping motions. The aim of this work was to develop modeling and analysis techniques for the dynamic aspects of this craft in two specific areas: waterjets and seakeeping. Specifically, due to the high sea states involved, the waterjet will undergo instances in which air will be ingested, causing propeller race and a corresponding uploading of the propulsion power. A second aspect that requires updated of current modeling techniques is the seakeeping characteristics throughout the mission. Towards this goal, we have employed state-of-the-art computational fluid dynamics (CFD) techniques combined with well-established modeling approaches to develop accurate and efficient simulation tools that will be particularly useful at the early stages of T-Craft design.

Structure and Analysis of the Z-Source MVDC Breaker

2011

Keith A Corzine, Robert W Ashton
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The medium-voltage dc (MVDC) architecture shows potential for future ship power systems. Components of the MVDC system are fairly well established; with the exception of circuit breakers. The main problem with the breakers in dc systems is the absence of a zero crossing in the current needed to extinguish an interrupting arc. Options for breakers in MVDC systems include over-sizing traditional ac breakers, hybrid mechanical/semiconductor breakers, and solid-state breakers. The recently introduced z-source breaker is most similar to the solid-state breaker, but has the additional feature of automatically responding to faults quickly and without the need for fault detection. Furthermore, the z-source breaker isolates the generation source from the fault current. This paper presents detailed analysis of the z-source breaker as well as variations on the topological structure. The various breaker options are validated through detailed simulation.

Dynamic Assessment and Co-Simulation of Thermal Management Strategies aboard Naval Surface Ships

2011

Thomas M. Kiehne
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The US Navy has committed to development of an all-electric ship (AES) that will incorporate significant advances in the areas of power management, advanced sensors and weaponry, reconfigurability, and survivability. Quantifying the close relationship between ship-board thermal, mechanical, and electrical sub-systems is of fundamental importance to understanding the nature of a large, integrated system like the AES. Research efforts in support of this development have focused on physics-based, dynamic models of thermal components and subsystems that approximate, at the system-level, the notional architecture of an AES. This research has resulted in the development of a general purpose thermal management tool coded in C++ and known as the Dynamic Thermal Modelling and Simulation (DTMS) framework. The DTMS simulation environment provides the ability to model thermal systems and subsystems relevant to the AES. The summary presented here describes the modelling approach used in DTMS and provides several examples of its use in large, complex, system-level, dynamic simulations. These examples include: • the thermal aspects of an integrated electric power system with component models for gas turbine engines, synchronous generators, motor converters, propulsion motors, and fixed-pitch propellers. • a dynamic model for a 200-ton, vapour-compression, marine chiller incorporating two-phase flow and heat transfer that is coupled to thermal loads representing shipboard compartment thus allowing investigation of system response during full-load and part-load operation. • a dynamic, co-simulation that links a thermally dependent electrical power distribution network, and its consequent transient heat loads, with a thermal resistive heat flow network that connects these loads to the thermal management network at the system-level. Thus, a thermally dependent electrical network has been integrated into a thermal management simulation environment with the intent of replacing what are traditionally modelled as steady-state heat loads with dynamic, thermally dependent, electrical loads.

Conserving Energy with No Watt Left Behind

2011

Steve Leeb, James Kirtley
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From p.2: Our research group has invented a new way to collect electrical usage data with a greatly reduced investment in sensors [3], [4]. Our “non-intrusive load monitor” or NILM can determine the electrical operating schedule of a collection of loads from a single measurement of aggregate current flowing to the loads. The Nonintrusive Load Monitor addresses the “sensor problem” for electric load monitoring by extracting information about individual loads from limited measurements at an easy-to-access, centralized location [3-8].

Use of Real Time Digital Simulation and Hardware in the Loop to De-Risk Novel Control Algorithms

2011

S. Loddick, U. Mupambireyi, S. Blair, A. Roscoe, K. Daffey, J. Watson
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Low power demonstrators are commonly used to validate novel control algorithms. However, the response of the demonstrator to network transients and faults is often unexplored. The importance of this work has, in the past, justified facilities such as the T45 Shore Integration Test Facility (SITF) at the Electric Ship Technology Demonstrator (ESTD). This paper presents the use of real time digital simulation and hardware in the loop to de-risk a innovative control algorithm with respect to network transients and faults. A novel feature of the study is the real time digital simulation and hardware

DC Fault Protection in Shipboard Power Systems using Z-Source Breakers

2011

Pradya Prempraneerach, George Em Karniadakis, Chryssostomos Chryssostomidis
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DC faults may cause severe disruptions in continuity of service to vital loads in a shipboard integrated power system, hence detection, isolation and protection against dc faults must be incorporated in both medium-voltage dc and low-voltage dc systems. A standard z-source breaker can identify and de-energize a faulty dc load on both buses quickly. However, until now, provisions for re-energizing have not been described. In this paper, a new z-source breaker is designed and control and detection techniques to identify the fault duration as well as to re-energize the load efficiently once the fault is cleared are developed. Dc fault characteristics on both medium- and low-voltage dc buses in a complete model of the all-electric-ship are demonstrated and the effective use of the new z-source breaker for the re-energizing process in protecting and restoring the continuity of ship service with a minimal effect is investigated.

Evolution of Machinery Control Systems Support At the Naval Ship Systems Engineering Station

2011

Timothy Scherer, Jeffrey Cohen
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From introduction: This paper will discuss the support that NAVSSES has provided the fleet using a historical perspective to show how MCS support evolved. While the organization provides steam control systems and fluid systems automation as well as networks and bridge control systems, this paper focuses on the MCS product line. A discussion of the early support for gas turbine programs and their associated control systems will be presented to provide a perspective on how those programs influenced the current MCS organization. The progression of support from early programs through in-service engineering to leading modernization programs will be addressed throughout this paper.

Prediction of Performance and Maneuvering Dynamics for Marine Vehicles Applied to DDG-1000

2010

Louis-Philippe M. Menard
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Being able to accurately model the performance of ships is an integral part of the ship design process. A considerable amount of money is invested into predicting how a ship will maneuver in a given sea state. Furthermore, it is vital to understand the powering requirements and potential limitations of the ship design. Typically, a physical scale model of the ship is constructed and experimented on in a tow tank to determine the hydrodynamic characteristics of the ship to be built. This can also be expensive. Therefore, there is considerable interest in developing a means to predict the hydrodynamic performance of a ship using alternative means. This thesis presents an analytical determination of the hydrodynamic coefficients for the DDG-1000 and compares them to an existing physical model with the intent to use the physical model as a substitute. Using analytical methods from several established sources, this thesis develops a simulated model for the DDG-1000 that is consistent with expected performance of a ship of this size and class. In addition, this thesis presents a model for the all-electric ship using azimuthing propellers. The analytically determined maneuvering dynamics are applied to the full all-electric ship system model, which incorporates the main generating engines through the power electronics to the motor and propulsion shafts. The results of the simulation form a baseline, from which future optimization of the model can occur.

Architectural Model to Enable Power System Tradeoff Studies

2010

Chryssostomos Chryssostomidis, James Kirtley, Matthew Angle
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We continue the development of an overall architectural model for an all-electric ship using a physics-based simulation environment to perform fully-integrated simulation of electrical, hydrodynamic, thermal, and structural components of the ship operating in a seaway. The goal of this architectural model is to develop an early-stage design tool capable of performing tradeoff studies on concepts such as AC vs. DC distribution, frequency and voltage level, inclusion of reduction gears, energy and power management options, and effect of arrangements and topology. The results of the studies will be presented in standard metrics including cost, weight, volume, efficiency/fuel consumption, reliability and survivability. We will specifically look at the hull, mechanical and electrical (HM&E) systems that support the ship and its missions; specifically, the electrical generation and distribution system, propulsion equipment, fresh- and saltwater pumping and distribution, control systems, and structural components. We have previously reported the creation of a basic design tool which uses hullform, drive train particulars, and operational employment of the vessel to determine resistance, powering and fuel usage. Specific advancements reported herein include: • Notional Ship modeled in Paramarine • Electrical Load Analysis and Prioritization • In-zone Distribution Equipment Modeling • Metrics Development o Survivability Metric o Graph Theory Applied to the Survivability Metric

Architectural Model to Enable Power System Tradeoff Studies (PowerPoint presentation)

2010

Chryssostomos Chryssostomidis, Julie Chalfant, David Hanthorn
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Presentation to the ESRDC Consortium of the paper, MIT, January 11, 2010.

Spectral Element/Smoothed Profile Method for Turbulent Flow Simulations of Waterjet Propulsion Systems

2010

Xian Luo, Chryssostomos Chryssostomidis, George Em Karniadakis
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We have developed fast numerical algorithms [1] for flowswith complex moving domains, e.g. propellers in free-space and impellers in waterjets, by combining the smoothed profile method (SPM, [2, 3, 4]) with the spectral element method [5]. The new approach exhibits high-order accuracy with respect to both temporal and spatial discretizations. Most importantly, the method yields great computational efficiency as it uses fixed simple Cartesian grids and hence it avoids body-conforming mesh and remeshing. To simulate high Reynolds number flows, we incorporate the Spalart-Allmaras turbulence model and solve the unsteady Reynolds-averaged Navier-Stokes (URANS) equations. We present verification of the method by studying the turbulent boundary layer over a flat plate. We show that both the eddy viscosity and velocity fields are resolved very accurately within the boundary layer. Having developed and validated our numerical approach, we apply it to study transitional and turbulent flows in an axial-flow waterjet propulsion system. The efficiency and robustness of our method enable parametric study of many cases which is required in design phase. We present performance analysis and show the agreement with experimental data for waterjets.

Study of Parallel AC and DC Electrical Distribution in the All-Electric Ship

2010

Julie Chalfant, Chryssostomos Chryssostomidis, Matthew G. Angle
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Medium-voltage DC electrical distribution is envisioned as a possible system for the warship of the future, bringing numerous advantages including a very power-dense architecture. This system takes the AC power produced by generators, immediately rectifies all power to DC and distributes it throughout the ship, requiring inversion back to AC for all AC loads. The question then arises whether it makes sense instead to route two parallel buses: an AC bus for all 60 Hz. AC loads and a DC bus to service all other loads. We model these two theoretical distribution systems in a notional destroyer using a preliminary design tool under development in our laboratory and find that the two-bus system is more efficient and lighter.

Propeller blade stress estimates using lifting line theory

2010

Brenden Epps, Jerod Ketcham, Chryssostomos Chryssostomidis
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OPENPROP, an open-source computational tool for the design and analysis of propellers and horizontal-axis turbines, is extended to provide estimates of normal stresses in the blades for both on- and off-design operating conditions. The numerical model is based on propeller lifting theory, and the present implementation of the code includes an analysis capability to estimate the off-design performance of the propeller or turbine and to make blade stress predictions. As an example, we present the design and performance of a two-bladed propeller. Experimental measurements of the propeller performance over a wide range of off-design operating conditions agree with performance predictions. Estimates of the blade stress are given for on-design and offdesign operating states of the propeller.

Dynamic Simulation of Ship-System Thermal Load Management

2010

Patrick T. Hewlett, Thomas M. Kiehne
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Anticipating highly dynamic and reconfigurable future ships, the US Navy has sought to develop modeling and simulation capabilities for transient, electrical-mechanical-thermal, shipboard interactions at the system level. In support of this work, an object-oriented Dynamic Thermal Modeling and Simulation (DTMS) framework written in C++ has been in use for several years. As reported in this paper, DTMS has recently been augmented to model two-phase flow and heat transfer for simulation of a shipboard vapor-compression chiller and its attendant loads. A controls methodology has been implemented in the heat exchanger models to monitor their relevant states, chilled water enthalpy, and refrigerant liquid level. These heat exchangers have been integrated with a heavily-customizable, centrifugal compressor model focused on required power input rather than the detailed dynamics of fluid compression. The heat exchangers and centrifugal compressor, along with a model of a thermostatic expansion valve, have been used to assemble a simulation of a 200-ton marine chiller predicated on baseline parameters for the Navy's current destroyer. This chiller has been connected with thermal loads of varying magnitude to demonstrate controller response during full-load and part-load operation. The final simulation reported here consists of 22 thermal loads ranging from 8 to 256 kW with chilled water supplied by two chillers. Results are compared with both steady-state-predicted values and previous dynamic simulations using commercial software.

Thermal Aspects of a Shipboard Integrated Electric Power System

2010

Christopher R. Holsonback, Thomas M. Kiehne
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Development and validation of a dynamic model focused on thermal aspects of the integrated propulsion system (IPS) on a notional all-electric ship (AES) is presented. This model serves as a baseline for investigation of thermal management technologies and architectures focused on identifying tradeoffs, improving system-level efficiency, and increasing the performance of an AES. The IPS model includes component models for gas turbine engines, synchronous generators, motor converters, propulsion motors, fixed-pitch propellers, and a ship hull. These component models are integrated into a system-level simulation and dynamic results for a ship-maneuver called a “crash-back” are presented. The resulting thermal-mechanical dynamics are discussed in depth.

Network Reliability With Geographically Correlated Failures

2010

Sebastian Neumayer, Eytan Modiano
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Fiber-optic networks are vulnerable to natural disasters, such as tornadoes or earthquakes, as well as to physical failures, such as an anchor cutting underwater fiber cables. Such real-world events occur in specific geographical locations and disrupt specific parts of the network. Therefore, the geography of the network determines the effect of physical events on the network's connectivity and capacity. In this paper, we develop tools to analyze network failures after a `random' geographic disaster. The random location of the disaster allows us to model situations where the physical failures are not targeted attacks. In particular, we consider disasters that take the form of a `random' line in a plane. Using results from geometric probability, we are able to calculate some network performance metrics to such a disaster in polynomial time. In particular, we can evaluate average two-terminal reliability in polynomial time under `random' line-cuts. This is in contrast to the case of independent link failures for which there exists no known polynomial time algorithm to calculate this reliability metric. We also present some numerical results to show the significance of geometry on the survivability of the network and discuss network design in the context of random line-cuts. Our novel approach provides a promising new direction for modeling and designing networks to lessen the effects of geographical disasters or attacks.

DTMS: A Framework for System-Level, Dynamic Simulations across Multi-Disciplinary Boundaries

2010

Michael S. Pierce, Thomas M. Kiehne
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The US Navy has committed to development of an all-electric ship (AES) that will incorporate significant technical advancements in the areas of power management, advanced sensor equipment and weaponry, reconfigurability, and survivability systems while simultaneously increasing overall system efficiency and decreasing operational costs. Research efforts in support of this development have focused on physics-based, dynamic models of thermal components and subsystems that approximate, at the system-level, the notional architecture of an AES. This research has resulted in the development of a general purpose thermal management tool coded in C++ and known as the Dynamic Thermal Modeling and Simulation (DTMS) framework. Using numerical approximations of complex physical behaviors, the scope of the DTMS framework has been expanded beyond elements of thermal-fluid behavior to capture the dynamic nature of far broader, more complex architectures containing interconnected thermal-mechanical-electrical components. The summary presented here describes the modeling approach used in DTMS and provides several examples of its use in large, complex, system-level, dynamic simulations.

Investigating the influence of zero sequence impedance in ship ungrounded electric networks

2010

J. M. Prousalidis
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In shipboard installations ungrounded earthing is selected because it provides continuous power supply, even in the case of single-phase earth faults, which cannot be accomplished by low resistance earthing in the neutral point of wye-connected generator or transformer windings. However, the electric network is actually earthed via the high impedance capacitances of all the equipment installed onboard. Therefore, as already discussed in literature, the 'ungrounded' earthing type of shipboard installations has to be treated as 'grounded' via capacitive elements. This paper aims to show, for the first time, an analytical description of statements given in previous publications, ie, that in all analyses performed, it is the entire zero sequence (homopolar) impedance that has to be taken into account. This homopolar impedance includes, among others, leakage capacitances of the entire electrical installation. Therefore, an investigation of the influence of the zero sequence impedance is performed in representative case studies, all referring to unbalanced operating conditions. Within this frame, analytical expressions of voltages and currents with respect to zero sequence impedance are yielded. Moreover, the significant adverse effects of leakage capacitances on the occasion of an actual ship earthing network, are highlighted.

Thermal-Electric Co-Simulation of Power Conversion Systems aboard an All-Electric Ship

2010

Mathew A. Pruske, Thomas M. Kiehne
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A model has been built to link a shipboard electrical power system, and its consequent heat loads, with an in-house thermal simulation framework specifically created to address issues of shipboard thermal management in a dynamic, system-level sense. An electric power model was created to capture the transient nature of heat dissipation as a function of the dynamic nature of power converter modules in an electrical, power distribution network. The power network was then mated with a thermal resistive network that links the heat loads to the thermal management network. The resulting network is dynamic in nature and captures the essential transient characteristics of heat flow and energy storage while accommodating the greatly disparate time scales inherent to thermal and electrical networks.

EOF-based constrained sensor placement and field reconstruction from noisy ocean measurements: Application to Nantucket Sound

2010

Xiu Yang, Daniele Venturi, Changsheng Chen, Chryssostomos Chryssostomidis, George Em Karniadakis
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Sensor placement at the extrema of empirical orthogonal functions (EOFs) is efficient and leads to accurate reconstruction of the ocean state from a limited number of measurements. In this paper, we develop important new extensions of this approach that optimize sensor placement to avoid redundant measurements, employ imperfect EOF modes, and take into account measurement errors. We use the simulation outputs of the Finite Volume Community Ocean Model applied to the Nantucket Sound region to evaluate the performances of the new approach and compare it against other similar techniques. Specifically, we find that there exists a critical size of exclusion volume (whose value is unknown a priori) surrounding each sensor that prevents clustering of sensors while minimizing the reconstruction error. In addition, we propose a new algorithm that can be effective in incorporating gappy data in assimilation schemes. We also derive analytical formulas of the uncertainty in the reconstructed field given any inaccuracies in the measurements. Taken together these developments will aid further in the development of truly real-time adaptive sampling for ocean forecasting.

Science and Technology Challenges and Potential Game-Changing Opportunities

2010

Michael Triantafyllou
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The future of naval engineering in the 21st century will be shaped by novel and emerging technologies that will not only provide unprecedented capabilities but also require radical rethinking of naval ship and vehicle design. This change is already in the works as engineering schools in major universities are hiring young faculty trained in new fields and developing novel technologies. This investment is expected to bring radical changes to mature fields, such as naval architecture and marine engineering; hence, to fully reap the benefits the ground must be prepared now. The paper is structured around these new emerging technologies and the impact they are expected to have and provides discussion on their impact on naval ships and vessels and their capabilities. Traditional mechanical engineering departments and naval architecture and marine engineering schools are turning increasingly towards nano-engineering, novel power-trains and synthetic fuels, and robotic devices and smart sensors, in order to revitalize mature disciplines. The following emerging technologies and fields are covered and a discussion of the related implications for naval ship design is included: • Efficient power trains (especially of the hybrid type), efficient engines using alternative fuels that are more sustainable and environmentally friendly, and fuel cells that use conventional fuels more efficiently. • Progress in surface chemistry that allows the development of novel coatings to protect ship hulls and cargo holds, reduce deposits in pipelines, and decrease fluid drag. • Work on the all-electric ship, which has generated new methods to design and operate ships with increased automation, reduced manning, and increased reliability. • New sensor arrays, which will allow sensing of the self-generated flow and will create the capability for active flow manipulation and hence increased capabilities for maneuvering and efficient propulsion. • Robotic developments that promise routine unmanned inspection and remote underwater intervention. • Smart autonomous underwater vehicles (AUV) that increase substantially the operational capability of ships and submarines. Naval ship and submarine design will be influenced significantly to accommodate the storage and servicing, as well as the launching and retrieval of AUVs in rough weather. • New high-strength steels that improve hull protection against impact and fatigue, including operation in very cold climates. • Global ocean modeling and prediction that will allow effective routing and operation of vessels in rough seas with unprecedented detail. The paper concludes with an assessment of the shape of future naval designs and the capabilities they will offer.

Medium Voltage DC Testbed:Generator System GS-1

2009

Michelle Bash, Ricky R. Chan
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In this paper, a description of the generation system GS-1 which is part of the medium voltage dc (MVDC) testbed is set forth. This paper describes the control strategy as well as three mathematical models of GS-1. These models vary in the level of detail, from the non-linear average value model (AVM) to the highly detailed model that incorporates a brushless excite machine model.

Medium Voltage DC Testbed: Propulsion Drive

2009

Cahya Harianto
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This report will describe the propulsion drive as a part of the medium voltage dc system. The propulsion drive is based on an induction machine (IM) driven using a fully controlled three-phase bridge inverter with an input filter. Four simulation models will be described, namely a detailed waveform model, a simplified waveform model, and a detailed non-linear average value model, and a simplified non-linear average model, non-linear average value model, and a simplified non-value model.

Quarterly Report On the Contributions from MIT to the Electric Ship Research and Development Consortium, January-March, 2009

2009

Chryssostomos Chryssostomidis, Franz Hover, George Em Karniadakis, James Kirtley, Steven Leeb, Michael Triantafyllou
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1. EXECUTIVE SUMMARY CHRYSSOSTOMIDIS/KARNIADAKIS: We have continued the development of an end-to-end simulation system for the All-Electric Ship (AES), including both the Integrated Power System (IPS) and Hydrodynamics. The new tasks completed are: (1) Sensitivity study of the 15-phase Induction Machine (IM) controller. (2) Modeling of the combustion turbine that drives the Synchronous Machine (SM). We present some technical details below and some representative results for both cases. In future work we will present simulation and sensitivity results of the full system for different scenarios. HOVER: We investigate the robustness of integrated power system layouts from a network theoretic perspective. We develop a new design methodology based on random network theory, in which network generation parameters are optimized for robustness to failures. Two approaches are proposed, one in which an entire network is optimized, and another in which a network added to a preexisting design is optimized. This latter approach allows given designs (line diagram detail) to be explored from a robustness perspective, without resorting to adding significant detail and running extensive simulation. KIRTLEY: The main new accomplishment of this past quarter was the development of a basic motor estimation program to be used with existing propeller design software to jointly optimize designs of motor driven propellers. The existing 150 and 300 rpm, 19 and 38 MW, induction motor designs were also adapted to optimize operation at intermediate speeds of 200 and 250 rpm in order to verify the roughly linear dependence of the motor decrease in weight with increased shaft speed. The linear dependence results in weights slightly smaller than theoretically expected but still achievable if slightly increased heating of the rotors is allowed. LEEB: We have developed a nonintrusive power monitor for shipboard applications. Experiments with this monitor are reported in [2]–[12]. This power system diagnostic monitor uses existing power wiring to monitor loads. It is lightweight, cheap to install, and, because of its low sensor count, potentially highly reliable. References [13]–[19] demonstrate the NILM as a potentially effective tool for evaluating and monitoring shipboard mechanical systems through analysis of electrical power data. A key advantage of the nonintrusive approach is the ability to reduce sensor count by monitoring collections of loads. The arrangement of the power wiring for these collections of loads determines the performance, accuracy, and usefulness of the NILM. During the reporting period we have conducted an analysis of the tradeoffs that affect the likely performance of the NILM in a real world environment, e.g., on board the USCGC Escanaba (WMEC-907) in Boston, MA. These tradeoffs bound the size of the collection of loads that can be monitored, determining the extent of the “nonintrusiveness” that the monitoring system can deliver in practice. A new ASNE publication of our analysis was published during the reporting period. We have analyzed data from a Fall 2008 operational cruise of the ESCANABA, and conducted experiments that permitted the serving crew to use the NILM and its data for underway maintenance and for ensuring mission readiness. As is indicated in the attached letter, the crew found the NILM highly valuable in performing condition based maintenance (CBM) and underway repairs to maintain mission readiness. TRIANTAFYLLOU: In accordance with our plan, we developed further our models and employ them to study the response of a ship in a seaway. We developed all models for the hull, propeller, engine, generator, and motor, and included maneuvering equations for the all-electric ship in a seaway. We developed control protocols and simulated the response of the ship under transient conditions.

Optimization of Direct Drive Induction Motors for Electric Ship Propulsion with High Speed Propellers

2009

Steven Englebretson, James Kirtley, Chryssostomos Chryssostomidis
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Direct drive electric ship propulsion can offer increased flexibility and reduced overall fuel consumption compared to geared mechanical systems [Davis 1987, Doerry 2007]. As a well-established technology, induction motors are a dependable and economical option for electrically controlled ship propulsion, but their size and weight are large due to the relatively low propeller speeds. Increasing the propeller speed allows the design of higher speed motors of comparable efficiency and significantly decreased size and weight. This paper first presents a typical steady-state circuit model of a ship propulsion motor based on published data of an existing 19 megawatt machine. Design variables and constraints specific to this application are discussed before comparing designs adapted to minimize size and weight for driving higher speed propellers. Predicted drive motor total size and weight decrease with increasing full load rotational speed. A basic examination of the motor cooling is also included to verify the feasibility of the new design and investigate possible limiting cases taking advantage of direct water-cooled conductors.

Fast 3D Flow Simulations of a Waterjet Propulsion System

2009

Xian Luo, Chryssostomos Chryssostomidis, George Em Karniadakis
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In this paper we present a new method to simulate 3D flow in complex-geometry moving domains and we apply it to study the flow patterns in a waterjet-like system. In particular, we combine the spectral element method [5] with the smoothed profile method (SPM, [11], [12] and [14]), an approach similar in spirit to the popular immersive boundary method but more suitable for high-order methods. SPM uses a fixed nonconforming mesh and represents the moving domains by smooth profiles, which are used to construct a penalty force term in the Navier-Stokes equations. Its similarity with the immersed boundary method is that they both use a force distribution to effectively impose the constraints associated with the flow boundary conditions. However, for spectral element discretizations, the smooth profile of SPM leads to high-order accuracy as it does not cause Gibbs phenomena at the geometric interfaces. We analyze the accuracy of the new hybrid method for a prototype flow problem and show that the modeling error (due to smooth profiles) is a non-monotonic function of the time step size and the interface thickness of the smooth profile. This new method is applied to simulate 3D complexgeometry moving domains such as propellers in free-space and impellers in ducts, which are key components of the waterjet propulsion system. We present flow results for various rotational speeds, Reynolds numbers, and pressure gradients in order to elucidate the mechanisms of thrust generation in waterjet systems. In terms of computational efficiency of the method, the new approach is more than 100 times faster than using the often-employed arbitrary Lagrangian Eulerian (ALE) for simulations in moving domains and can be run on single processor computers.

Efficient Sensor Placement for Ocean Measurements Using Low Dimensional Concepts

2009

Yildrim Battalgazi, Chryssostomos Chryssostomidis, George Karniadakis
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Using simulation results from three different regional ocean models (HOPS, ROMS and FVCOM) we show that only a few spatio-temporal POD (proper orthogonal decomposition) modes are sufficient to describe the most energetic ocean dynamics. In particular, we demonstrate that the simulated ocean dynamics in New Jersey coast, Massachusetts Bay and Gulf of Maine is energetically equivalent to the wake dynamics behind a cylinder at low Reynolds number. Moreover, the extrema of the POD spatial modes are very good locations for sensor placement and accurate field reconstruction. We employ a modified POD theory to incorporate a limited number of measurements in reconstructing the velocity and temperature fields, and we study systematically the corresponding reconstruction errors as a function of the sensor location, number of sensors, and number of POD modes. This new approach is quite accurate in short-term simulation, and hence it has the potential of accelerating the use of real-time adaptive sampling in data assimilation for ocean forecasting.

Scalability of Non-intrusive Load Monitoring for Shipboard Applications

2009

James Paris, Zachary Remscrim, Steve Leeb, K. Dougals, R. W. Cox, S. T. Galvin, S. G. Coe, J. R. Haag, J. An. Goshorn
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The non-intrusive load monitor has been demonstrated as an effective tool for evaluating and monitoring shipboard electro-mechanical systems through analysis of electrical power data. A key advantage of the non-intrusive approach is the ability to reduce sensor count by monitoring collections of loads. This paper reviews trade-offs that affect the likely performance of the NILM in a real world environment.

Field Demonstration of a Real-time Non-intrusive Monitoring System for Condition-based Maintenance

2009

Ethan Proper, Robert W Cox, Steve Leeb, K. Douglas, J. Paris, W. Wichakool, E. L. Foulks, R. Jones, P. Branch, A. Fuller, J. Leghorn, G. Elkins
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The performance of important electrical loads on mission critical systems like warships or off-shore platforms is often tracked by dedicated monitoring equipment. Individual monitoring of each load is expensive and risky. Expense occurs because of the need for individual sensors and sensor wiring for every load of interest. Reliability is compromised because detected failures or fault conditions might legitimately be due to load failure, but might also be due to errors or failure in the sensor network or recording instruments. The power distribution network on a warship could be pressed into “dual-use” service, providing not only power distribution but also a diagnostic monitoring capability based on observations of the way in which loads draw power from the distribution service. This paper describes field tests of a prototype system that monitors multiple loads using existing electrical wiring. Initial results are presented from a device that monitors a small collection of motors and two other devices that monitor an entire engine room.

Functions of PCon

2009

Norbert H. Doerry
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Voltage Regulator and Parallel Operation

2009

Basler Electric
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Generator sets are operated in parallel to improve fuel economy and reliability of the power, Because of advantages of parallel operation, multiple generator installation has become common in applications for standby and prime power, portable and stationary power, commercial and military power; and they continue to grow. This paper focuses on the control of the voltage regulator when operating generators in parallel.

Induction Machine Stray Loss from Inter-bar Currents, PhD Thesis

2009

Steven C. Englebretson
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Stray load loss refers generally to the sources of induction machine loss not accounted for by typical calculations of primary or secondary copper loss, no load core loss, or friction and windage loss. Harmonic rotor bar currents from the non-sinusoidal distribution of the slotted stator winding contribute significant stray load loss. Rotor bars, especially on cast rotors for machines under fifty horsepower (37.3 kW), can be skewed, helically twisted from one end to the other, to reduce loss, torque, and noise from alignment of rotor and stator slots and from harmonic rotor currents. Inter-bar currents °owing circumferentially through the laminations between skewed and non-insulated rotor bars can significantly increase stray load loss. Presented equations adjust the effective rotor resistance and skew factor of the extended per-phase induction machine equivalent circuit model in order to account for the impact of inter-bar currents. The average value of resistance between neighboring rotor bars significantly impacts calculations of rotor bar and inter-bar current and loss and has been determined for a number of measured rotors. Rotors ¯t into one of two distinct categories where either the bar-to-lamination contact resistance dominates the inter-bar resistance or the total resistance divides more equally between values of bar, lamination, and contact resistance. Performance calculations using the adjusted equivalent circuit model are verified theoretically against previous calculation methods and experimentally by comparison to measured test results including variations in rotor skew, conductor conductivity, and inter-bar resistance. A number of different cast copper and aluminum five and ten horsepower test induction motors performed differently than originally predicted and variably between nominally identical machines. Inter-bar currents are part of the cause of both the variation and additional losses measured on these machines. The adjusted equivalent circuit equations improve estimations of motor performance and allow identification of means to increase machine efficiency by minimizing the stray load loss due to inter-bar currents.

MIT ESRDC 2010 Work Plan

2009

Chryssostomos Chryssostomidis, Julie Chalfant, Franz Hover, George Karniadakis, James Kirtley, Steven B. Leeb, Mirjana Milosevic Marden, Michael Triantafyllou,
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Annual Report (2008-2009) On the Contributions from MIT To the Electric Ship Research and Development Consortium

2009

Chryssostomos Chryssostomidis, Franz Hover, George Karniadakis, James Kirtley, Steven Leeb, Michael Triantafyllou
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Sequential Sparse Matching Pursuit

2009

Radu Berinde, Piotr Indyk
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We propose a new algorithm, called Sequential Sparse Matching Pursuit (SSMP), for solving sparse recovery problems. The algorithm provably recovers a k-sparse approximation to an arbitrary n-dimensional signal vector x from only O(k log(n=k)) linear measurements of x. The recovery process takes time that is only near-linear in n. Preliminary experiments indicate that the algorithm works well on synthetic and image data, with the recovery quality often outperforming that of more complex algorithms, such as l1 minimization.

Integrated Contra-Rotating Propulsion Drives for Thurst-Dense Propulsion Systems

2009

Chryssostomos Chryssostomidis, James Kirtley, A. Slocum, Julie Chalfant
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As the Navy moves forward with electric-propulsion based ships, there is clearly a significant motivation for reducing the size, fuel consumption and life-cycle cost of the largest electrical load – the propulsion system. We have identified several technologies that, when used in conjunction, have the potential to significantly improve the efficiency of the propulsion system while simultaneously significantly reducing the associated weight and volume. Thus, we propose basic research into an alternative propulsion scheme involving three specific technologies: contra-rotating propellers, contra-rotating motors, and doubly-fed motors. In particular, an integrated contra-rotating propulsion system will be considered. In this system, two axially-aligned contra-rotating propellers are used; such an arrangement has significant hydrodynamic and thus fuel-saving benefits. However, the salient feature of the proposed arrangement is that rather than turning each propeller with its own dedicated motor, the two propellers will be driven by a single contra-rotating machine. For a given propulsion power requirement, such a machine will operate at twice the speed but half the torque of a conventional single-motor single-propeller arrangement. This translates into a reduction of machine mass by over one-half. Further, the contra-rotating machine could be doubly-fed, resulting in a motor of equivalent size to the standard contra-rotating machine, but with power electronics sized at about one-fifth of that for a singly-fed machine.

End-to-End Simulator for the All-Electric Ship MVDC Integrated Power System

2009

M. Milosevic M. Marden, Pradya Prempraneerach, James Kirtley, George Em Karniadakis, Chryssostomos Chryssostomidis
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In this paper, a large scale Medium Voltage DC all-electric ship integrated power system is modeled from the prime mover (gas turbine) to the propulsion load. This system has a three-phase 21MW synchronous machine as a main generator and a three-phase 19MW induction motor as a main propulsion drive. The in?uence of propeller emergence on both electrical and mechanical components of the system is investigated.

Simple Reactive Obstacle Avoidance Algorithm and Its Application in Singapore Harbor

2009

Tirthankar Bandyophadyay, Lynn Sarcione, Franz Hover
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Autonomous surface craft (ASC) are increasingly attractive as a means for performing harbor operations, including monitoring and inspection. However, due to the presence of many fixed and moving structures such as pilings, moorings, and vessels, harbor environments are extremely dynamic and cluttered. In order to move autonomously in such conditions, ASC’s must be capable of detecting stationary and moving objects and plan their paths accordingly. We propose a simple and scalable online navigation scheme, wherein the relative motion of surrounding obstacles is estimated by the ASC, and the motion plan is modified accordingly at each time step. Since the approach is model-free and its decisions are made at a high frequency, the system is able to deal with highly dynamic scenarios. We deployed ASC’s in the Selat Pauh region of Singapore Harbor to test the technique, using a short-range 2D laser sensor; detection in the rough waters we encountered was quite poor. Nonetheless, the ASC’s were able to avoid both stationary as well as mobile obstacles, the motions of which were unknown a priori. The successful demonstration of obstacle avoidance in the field validates our fast online approach.

Toward the Development of an Integrated Electric Ship Evaluation Tool

2009

Julie Chalfant, Chryssostomos Chryssostomidis
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With the advent of energy-intensive weapons and sensor systems visualized for future United States Navy surface combatants, the design of Navy ships is turning to the all-electric ship as a potential solution that enables power sharing between propulsion and other loads. One ramification of the allelectric option is that the resulting electric-drive propulsion systems can be configured such that the motor is directly coupled to the propeller, thus eliminating the need for reduction gears. Current state-of-the-art propellers are rated for approximately 150 rpm; this relatively slow speed in a direct-drive configuration requires extremely large motors. For example, a typical destroyer-sized vessel capable of speeds up to 30 knots requires four motors each weighing approximately 120 metric tons and occupying 86 cubic meters. A high-speed propeller would allow a correspondingly higher speed motor, resulting in reduced motor weight and volume. Direct evaluation of the weight and volume savings is inadequate; an integrated approach must be used to account for secondary effects. After substituting the new motor and propeller in the baseline ship, we use their efficiencies in conjunction with a typical operating scenario to determine fuel usage.We evaluate cooling system load and make changes as appropriate to include resizing cooling water pumps if necessary. We then analyze layout and arrangements for any necessary changes such as additional tankage or pumping capacity. Overall ship performance including hydrostatic considerations such as draft and trim are evaluated. This total ship approach allows us to determine the net benefit realized from the high-speed propeller. Net benefits are then compared to the baseline ship to produce interesting tradeoffs such as increased range versus increased payload or designing a smaller ship. Such total ship analysis is valuable as designers go on to answer such questions as the proper distribution system for a particular application, or to analyze the impact of specific technology advances.

OpenProp: An Open-source Parametric Design and Analysis Tool for Propellers

2009

Brenden Epps, Julie Chalfant, Richard Kimball, Alexandra H Techet, Kevin Flood, Chryssostomos Chryssostomidis
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OpenProp is an open-source computational tool for the design and analysis of optimized propellers and turbines. The numerical model is based on the vortex lattice lifting line methods utilized by the US Navy as well as commercial designers. The code is written in MATLAB M-code, which is widely used in academia and industry. The code includes analysis capability to estimate the performance curve of a given design for use in off-design performance prediction. In addition, a module to generate cavitation bucket diagrams for cavitation analysis is presented. Examples of designs are presented including validation comparisons and examples of actual parts fabricated from the code using 3D printing technology . As a case study, we present the design and analysis of a propeller for an electrically-driven destroyer-sized twinscrew vessel. Herein, we explore the redesign of a propeller for a higher shaft rotation rate, in order to investigate the impacts on motor sizing within the limits of cavitation. Offdesign propeller performance is also predicted to aid in modeling the hydrodynamic performance and fuel usage of the ship operating over its typical operational profile.

OpenProp: An Open-source Design Tool for Propellers and Turbines

2009

Brenden Epps, M. J. Stanway, Richard Kimball
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An open-sourced computational tool for the design and analysis of optimized propellers and turbines is presented. The design tool, called OpenProp, is based on well-proven vortex lattice lifting line methods utilized by the US Navy as well as commercial designers. This paper presents the methodology and numerical implementation of OpenProp, with multiple examples of designs, including actual parts fabricated from the code using 3D printing technology.

DDG 1000 Engineering Control System (ECS)

2009

Mark Henry, Michael Iacovelli, Jeffrey Thatcher
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The Navy’s advanced multi-mission 21stcentury destroyer the USS ZUMWALT (DDG 1000) is well into the Detailed Design and Integration (DDI) and Detailed Design and Construction (DDC) phase. The highly advanced and integrated control system for the engineering plant, called the Engineering Control System (ECS), hierarchically supports the overall Ship Control System (SCS) to provide ship mobility and power to Combat Systems. Optimal manning objectives for DDG 1000 have driven ship system design to an unprecedented level of automation, and consequently the ECS is more complex than any other machinery control system ever developed for a Navy surface combatant. Software development is currently in detailed design phase while ECS hardware has progressed into production. This paper will explore the architecture and functionality of this distributed and hierarchical Engineering Control System that has emerged through years of evolution for Navy’s DDG 1000.

Analysis of Fault Events in MVDC Architecture

2009

A. Ouroua, J. Beno, R. Hebner
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Effective interruption of load currents under both normal and fault conditions presents major challenges in medium-voltage dc distribution systems. In a highly-integrated dc power system, the preponderance of power converters connecting several loads with power ranging from (W) to (MW) levels rises additional concerns about the effects of a dc fault on other loads connected to the same bus or adjacent buses. Equally critical are the interactions between these power converters during the fault isolation and clearance process. In order to address some of these issues, a basic model has been constructed to study the behavior and effects of dc faults in an MVDC power system for an all-electric ship. Results of the analysis are presented.

On Studying the Power Supply Quality problems due to Thruster Start-ups

2009

J. M. Prousalidis, P. Mouzakis, E. Sofras, D. Muthumuni, O. Nayak
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The target of this paper is twofold: primarily to highlight the significant effect of certain power supply quality problems on the normal operation of the entire ship grid, namely inrush currents and voltage dips due to manoeuvring thruster motor starting-ups. At a second stage, the paper aims at recommending some amelioration of standardization status. Hence, the authors suggest the exploitation of existing experience on pulsed load standardizing, taking into account the resemblance between the systems. The study is enriched by actual case studies and simulations in PSCAD computer program.

Assessing the Vulnerability of the Fiber Infrastructure to Disasters

2009

Sebastian Neumayer, Gil Zussman, Reuven Cohen, Eytan Modiano
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Communication networks are vulnerable to natural disasters, such as earthquakes or floods, as well as to physical attacks, such as an Electromagnetic Pulse (EMP) attack. Such real- world events happen in specific geographical locations and disrupt specific parts of the network. Therefore, the geographical layout of the network determines the impact of such events on the network's connectivity. In this paper, we focus on assessing the vulnerability of (geographical) networks to such disasters. In particular, we aim to identify the most vulnerable parts of the network. That is, the locations of disasters that would have the maximum disruptive effect on the network in terms of capacity and connectivity. We consider graph models in which nodes and links are geographically located on a plane, and model the disaster event as a line segment or a circular cut. We develop algorithms that find a worst- case line segment cut and a worst-case circular cut. Then, we obtain numerical results for a specific backbone network, thereby demonstrating the applicability of our algorithms to real-world networks. Our novel approach provides a promising new direction for network design to avert geographical disasters or attacks.

Design of the All-Electric Ship: Focus on Integrated Power System Coupled to Hydrodynamics

2008

Pradya Prempraneerach, James Kirtley, Chryssostomos Chryssostomidis, M. S. Triantafyllou, and G. E. Karniadakis
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We present a detailed model of the integrated power system coupled to hydrodynamics that allows us to study global sensitivities in the All-Electric Ship. A novel element of our formulation is the stochastic modeling of the coupled system to account for uncertainty in the parameters or operating conditions. This new computational framework is applied to a model of the DDG- 51 destroyer that involves a 19 MW 15-phase induction machine and an indirect field oriented controller. In particular, we simulate extreme events corresponding to propeller emergence and firing of pulsed power weapons.

Gradient-Free Stochastic Sensitivity Analysis of the Shipboard Power System

2008

Pradya Prempraneerach, J Foo, M. Triantafyllou, C. Chryssostomidis, and G. E. Karniadakis
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Sensitivity analysis results are useful both for the early design stage – where the parametric space can be substantially reduced – but also in operating conditions, e.g. of the future electric ship, resulting in reduced operational costs and increased reliability. Here we discuss variance-based methods to analyze the sensitivity of stochastic electro-mechanical systems with multirate dynamics. We present results for an illustrative example and for a model of an integrated power system.

Quarterly Report On the Contributions from MIT to the Electric Ship Research and Development Consortium, October-December, 2008

2008

Chryssostomos Chryssostomidis, Franz Hover, George Em Karniadakis, James Kirtley, Steven Leeb, Michael Triantafyllou
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1. EXECUTIVE SUMMARY CHRYSSOSTOMIDIS/KARNIADAKIS: We have developed a new computational framework consisted of detailed models for the two primary components of the All-Electric Ship (AES), namely Integrated Power System (IPS) and Hydrodynamics. This is the first time that all components of each system have been modeled and coupled together at this level. Simulating such a coupled system on today's computers is feasible, and results can be obtained in a matter of minutes even for long-time integration of the system to include the characteristic electric, mechanical and hydrodynamic scales. We note that these characteristic time scales, even of the small subcomponents, are not input to the problem but they are part of the solution, unlike other models where simplified lumped parameterizations are employed. This new computational framework is applied to a model of the DDG-51 destroyer that involves a 19 MW 15-phase induction machine (IM) and an indirect field oriented controller (IFOC). In particular, we simulate the extreme event of propeller emergence. HOVER: We investigate the robustness of integrated power system layouts from a network theoretic perspective. We find that an abstracted electric ship model based on a notional cruiser line diagram behaves more like an Erdos-Renyi random network than a scale-free network, and furthermore that scale-free networks are significantly less robust than random and notational cruiser-type networks, under the loading and failure conditions considered. A second area of research has been particle filtering. Specifically, we apply stochastic collocation, a tool we previously used for uncertainty analysis in the AES, to make sampling from proposal distributions more efficient, and hence increase the real-time applicability of particle filters. KIRTLEY: Our efforts this past quarter focused on the design and evaluation of motors to match reported specifications and performance for two different Alstom machines, a 19 MW, up to 150 RPM, motor and a 20 MW, up to 180 RPM, design. An IEEE paper, “The Advanced Induction Motor,” by Clive Lewis from the 2002 IEEE Power Engineering Society Summer Meeting describes both machines. As a physically realizable design, previously built and tested, the 19 MW machine provides a baseline for verifying the MIT motor evaluation software on a low speed, multi-megawatt motor as well as a realistic framework for examining design modifications. The initial designs were also altered for comparison with two different cases, first doubling the initial motor power output, speed, and frequency, and second doubling the speed and frequency while maintaining the original power output but with a reduced motor size and weight. After designing around the full load operating points, changes in motor efficiency with varying speed and corresponding load were also compared between designs. LEEB: Power system monitoring is an exciting approach for creating an inexpensive, highly capable “black-box” for monitoring the performance of critical shipboard systems. With remarkably little installation effort or expense, we have fielded a non-intrusive load monitor (NILM) that can reliably monitor and track diagnostic conditions for multiple devices. During the past quarter, we have worked to automate the recognition of load operation and diagnostic monitoring to make results available to the crew in real-time. To do so, we have developed a software package known as ginzu that eliminates the need for off-line analysis by a skilled observer. Initial tracking of load operation and diagnostic condition are now provided automatically by the NILM on-board ship. Furthermore, our field-tested systems have been installed at a central point that allows them to monitor multiple loads simultaneously. The ginzu software application implements a detect-classify-verify loop that locates electrical load transients, identifies them using a decision-tree-based expert classifier, and then generates event files that contain relevant information. Additionally, the ginzu application provides streaming data to a graphical user interface known as the Ginzu Graphical User Interface (GinzUI) TRIANTAFYLLOU: We developed robust models for ship hydrodynamics, including forward propulsion and maneuvering, as well as models for the propeller and the linear and nonlinear loads in a random sea-state; models for the gas turbine, generator, electric system, and motor. The models were developed at various levels of accuracy so as to assess the principal time constants and parameters of the system, and thorough testing of the power flow and transient dynamics was made. Controllers for the gas turbine, generator and motor were developed and tested. This led to a system that can be parameterized in terms of the significant parameters so as to perform sensitivity analysis and stochastic simulation. Simulations that involve random loads from the sea, random events such as propeller emergence, and maneuvering motions in a storm are possible with the models developed. Sensitivity tables exhibiting the parameter to parameter finite-amplitude sensitivity have been developed that allow time-varying assessment of the critical parameters.

ESRDC Annual Report FY08

2008

Chryssostomos Chryssostomidis, Franz Hover, George Karniadakis, James Kirtley, Steven Leeb, Michael Triantafyllou
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Executive Summary Probabilistic analysis and simulation of electric networks in transient states has not been very advanced due primarily to the lack of stochastic tools for time-dependent systems. The work at MIT has focused on developing such tools in the context of the All-Electric-Ship (AES). We have formulated efficient new methods in modeling uncertainty for electro-mechanical systems based on different extensions of polynomial chaos, and have applied them to various models extracted from the ONR Challenge problem. We have also developed new physical models to couple the ship hydrodynamics - and, hence, the randomness of sea states - to the integrated power system (IPS), thereby coupling the electrical, mechanical and hydrodynamic domains. In particular, in this report we review progress on several tasks: In the first one, results from stochastic simulations of the ONR integrated power system (IPS) testbed have been analyzed for sensitivities, and similar tests have been run on the real time digital simulator at the Center for Advanced Power Systems at Florida State University. We also explored applications of grid-based stochastic simulation techniques to nonlinear filtering. Further work on automating ship maneuvering has been performed, focusing on a hybrid approach that uses high-authority, open-loop maneuvers connected with simple “level” trajectories and feedback elements to control errors. The planning and control results have been tested extensively with scale model experiments. In other tasks, we employ a sensitivity method we developed for the AES to identify the most important parameters of the IPS under certain operating conditions. This information is then used to construct low-dimensional models for the IPS, which are very valuable for the efficient design of IPS. Specifically, we show that our low-dimensional models agree with the full (expensive) models even in the presence of 50% perturbations in the stochastic inputs. Finally, in the last task we develop new models that couple the ship motion and the propeller to the IPS, hence creating a new framework of analysis of IPS, the ship, and the sea states, for first time. Both simplified models but also full 3D solvers are involved in our analysis in order to obtain both accurate and efficient methodologies for the electric ship designer of future AES. The above results form a comprehensive framework based on which we plan to pursue future research activities of integrated power systems in mixed domains and design of AES under uncertainty. The impact of our work has been both on fundamental advances in stochastic modeling as well as on establishing a new modeling approach to AES. Many research groups within the ESRDC consortium and beyond have adopted the generalized polynomial chaos methods that we have developed.

Stochastic Modeling of Integrated Power System Coupled to Hydrodynamics in the All-Electric Ship

2008

Pradya Prempraneerach, James Kirtley, Chryssostomos Chryssostomidis, Michael S. Triantafyllou, and George E. Karniadakis
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In the paper, we model the integrated power system (IPS) of a typical destroyer ship coupled to hydrodynamics. This IPS is composed of a 21MW, 3-phase synchronous generator supplying electric power to 4160 V AC bus and to a 19 MW, 15-phase induction motor driven by an indirect rotor field oriented control for the motor torque. Moreover, stochastic responses are examined when there exists a variation in the induction motor’s rotor resistance and a disturbance from the slowly-varying added resistance, derived from a Pierson and Moskowitz sea spectrum.

Gradient-Free Stochastic Sensitivity Analysis of the Shipboard Power System

2008

Pradya Prempraneerach, J Foo, M. S. Triantafyllou, C. Chryssostomidis and G.E. Karniadakis
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Sensitivity analysis results are useful both for the early design stage – where the parametric space can be substantially reduced – but also in operating conditions, e.g. of the future electric ship, resulting in reduced operational costs and increased reliability. Here we discuss variance-based methods to analyze the sensitivity of stochastic electro-mechanical systems with multirate dynamics. We present results for an illustrative example and for a model of an integrated power. system.

Sensitivity Analysis and Low-Dimensional Stochastic Modeling of Shipboard Integrated Power Systems

2008

Pradya Prempraneerach, F. Hover, M. S. Triantafyllou, C. Chryssostomidis, and G.E. Karniadakis
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For design purposes, we use stochastic modeling and sensitivity analysis to identify the most important parameters of the AC power distribution in the Integrated Power System (IPS) model. The main AC subsystem of the IPS consists of a 59 kW synchronous generator and a motor drive of 50 hp induction motor. First, we perform sensitivity analysis treating all 31 parameters of the full model as stochastic variables. Second, we construct two lowdimensional stochastic models (with 15 and 8 parameters) and compare the multi-rate dynamics of the reduced models to the full model. For parameter variations larger than 50%, the low-dimensional models still predict accurately the mean values but underpredict the variance of most state variables.

Sensitivity Analysis and Low-Dimensional Stochastic Modeling of Shipboard Integrated Power Systems

2008

Pradya Prempraneerach, F. Hover, M. Triantafyllou, C. Chryssostomidis, and G.E. Karniadakis
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For design purposes, we use stochastic modeling and sensitivity analysis to identify the most important parameters of the AC power distribution in the Integrated Power System (IPS) model. The main AC subsystem of the IPS consists of a 59 kW synchronous generator and a motor drive of 50 hp induction motor. First, we perform sensitivity analysis treating all 31 parameters of the full model as stochastic variables. Second, we construct two lowdimensional stochastic models (with 15 and 8 parameters) and compare the multi-rate dynamics of the reduced models to the full model. For parameter variations larger than 50%, the low-dimensional models still predict accurately the mean values but underpredict the variance of most state variables.

Sensitivity Analysis of the Shipboard Integrated Power System

2008

Pradya Prempraneerach, Franz Hover, Michael Triantafyllou, Timothy J. McCoy , Chryssostomos Chryssostomidis , and George E. Karniadakis
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Stochastic sensitivity analysis is a valuable tool in ranking inputs and in investigating the degree of interaction of its components. In this paper, we present stochastic simulation results for a shipboard integrated power system and study its sensitivity. Specifically, we apply sensitivity analysis to two high-fidelity models of shipboard subsystems, investigating open- and closed-loop control of the propulsion system. The results show that different inputs are most important for the open- and closed-loop control, with sensitivities that change dramatically in time as they reflect the transition from the fast electrical scales to slower mechanical scales. We also demonstrate how sensitivity analysis can be used to establish the robustness of the AC drive.

Whitepaper: Role of the Combat Power Monitor in Zonal Electrical Distribution in the NGIPS

2008

Steve Leeb, James Kirtley
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First paragraph: The choice of future shipboard power system and the associated zonal electrical distribution system (ZEDS) will have a fundamental impact on the literal shape and configuration of future naval architectures. We propose, during a new phase of ESRDC work, to continue our development and study of ZEDS, and condition based maintenance and control techniques through ZEDS. We also propose to explore electric propulsion machinery that may ease the complexity and reduce the expense of future electric propulsion plants.

Assessing the Impact of Geographically Correlated Network Failures

2008

Sebastian Neumayer, Gil Zussman, Reuven Cohen, Eytan Modiano
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Communication networks are vulnerable to natural disasters, such as earthquakes or floods, as well as to human attacks, such as an electromagnetic pulse (EMP) attack. Such real-world events have geographical locations, and therefore, the geographical structure of the network graph affects the impact of these events. In this paper we focus on assessing the vulnerability of (geographical) networks to such disasters. In particular, we aim to identify the location of a disaster that would have the maximum effect on network capacity. We consider a geometric graph model in which nodes and links are geographically located on a plane. Specifically, we model the physical network as a bipartite graph (in the topological and geographical sense) and consider the set of all vertical line segment cuts. For that model, we develop a polynomial time algorithm for finding a worst possible cut. Our approach has the potential to be extended to general graphs and provides a promising new direction for network design to avert geographical disasters or attacks.

Fuzzy optimal allocation of spaces to zone-decks in general arrangements

2008

Eleanor Nick, Michael G. Parsons, Bruce Nehrling
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A general approach for the automated design of the general arrangements of naval vessels using fuzzy optimization is described. This process involves a series of two essentially two-dimensional problems: the allocation of spaces to Zone-decks (one deck within one vertical zone), and then the topological and detailed geometric arrangement of the spaces assigned to each Zone-deck. The development and testing of an efficient genetic algorithm that performs the optimal allocation process is described. The algorithm is used to optimize the allocation for a 70 space-12 Zone-deck test design that is representative of a full-scale small combatant.

Gradient Dynamic Optimization with Legendre Chaos

2007

Franz S Hover, Michael Triantafyllou
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We show that the gradient method for dynamic optimization (the Maximum Principle) can be applied in a stochastic sense using Legendre chaos, giving rise to a complete family of optimal trajectories, parameterized with a small number of free variables.

Overcurrent Protection on Voltage-Source-Converter-Based Multiterminal DC Distribution Systems

2007

Mesut E Baran, Nikhil R Mahajan
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This paper proposes a protection scheme which utilizes modern voltage-source converters as fast-acting current-limiting circuit breakers. This paper investigates the main challenges of detecting and localizing a fault, and interrupting it as quickly as possible in a multiterminal dc system. A system protection scheme consisting of smart relays associated with converters has been developed. The protection relays monitor local quantities to detect and isolate disturbances/faults. It is shown that overcurrent-based schemes can be adopted for these relays to meet the fast response requirements. The effectiveness of the proposed protection scheme is illustrated through simulations.

Modeling and Simulation of Electric Ships’ Power System Components and their Interaction

2007

A. Ouroua, J. R. Jackson, J. Beno, R. C. Thompson, E. Schroeder
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Models of propulsion motors, generators, gas turbines, and power converters are used to determine weights and volumes, evaluate designs, and predict performance of power system components for all-electric navy ships. The finite element analysis method using 3D CAD models is used to validate designs and predict performance under prescribed constraints that simulate realistic operational conditions. These models and analyses allow the development of complete, high-fidelity, design-based specifications of power system components before prototypes are built and tested. Examples of electromagnetic, mechanical, structural, thermal, shock and vibration analyses of models representing integrated designs of electric machines are presented. Modeling and simulation at system level play an equally crucial role in system architecture design. Simulation examples using a power system model for an all-electric ship are presented.

Stochastic Sensitivity Methods Applied to Shipboard Power Systems

2007

Pradya Prempraneerach, Franz Hover, Michael Triantafyllou, Chryssostomos Chryssostomidis, George Em Karniadakis
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In the design of large-scale and dynamic power systems, sensitivity analysis is an effective tool for ranking the importance of variations in governing parameters, and quantifying their interactions. In this work, we propose new methods for stochastic sensitivity analysis, which extend the standard approach by Morris. We apply these to subsystems of an all-electric ship model having multi-rate dynamics. This model consists of an AC power distribution grid and a propulsion system. In a startup transient, we identify the most important parameters in the short-time regime, where the electrical components dominate, and in the long-time regime where the mechanical components dominate.

Voltage dips in ship systems

2007

J. M. Prousalidis, E. Styvaktakis, E. Sofras, I. K. Hatzilau, D. Muthumuni
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In this paper, voltage dips (an important aspect of power quality) are presented in the context of ship power systems. Voltage dips are analyzed with respect to their origin (fault, motor starting, transformer saturation) considering the characteristics of the on-board installations. Emphasis is given to voltage dips and power quality issues of the all electric ship. Related issues are presented and discussed.

On the Design of Underwater Acoustic Cellular Systems

2007

Milica Stojanovic
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The design of a cellular underwater network is addressed from the viewpoint of determining the cell size and the frequency reuse pattern needed to support a desired number of users operating over a given area within a given system bandwidth. By taking into account the basic laws of underwater acoustic propagation, it is shown that unlike in the terrestrial radio systems, both the cell radius R and the frequency reuse number N must satisfy a set of constraints in order to constitute an admissible solution (which sometimes may not exist). The region of admissible (R, N) defines the possible network topologies. It is determined by the user density and the system bandwidth (rho, B), and by the required signal-to-interference ratio and per-user bandwidth (SIRo, Wo). The range of admissible solutions also depends on the choice of operating frequency region. Moving to a higher frequency region than that dictated by SNR maximization, improves the SIR and yields a greater system capacity.

Directly-Coupled Gas Turbine Permanent Magnet Generator Sets for Prime Power Generation On Board Electric Ships

2007

S. Z. Vijlee, A. Ouroua, L. N. Domaschk, J. H. Beno
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Prime power generation on board all-electric ships presents several options that affect fuel consumption, power density, operational effectiveness, and survivability. A study that aims at understanding the effects of some of these options has been conducted and results are reported in this paper. It is found that direct coupling of gas turbines to permanent magnet generators reduces system mass and volume significantly as compared to electric power generation systems installed on present-day navy ships. Furthermore, it is found that a significant benefit this topology brings is a reduction in gas turbine air duct volume if the compact gen-set units are relocated on or near the ship's upper decks. In addition, a combinatory analysis revealed that the choice of the number of generating units and their respective power levels has a significant influence on overall efficiency.

Application of Polynomial Chaos in Stability and Control

2006

Franz S Hover, Michael Triantafyllou
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The polynomial chaos of Wiener provides a framework for the statistical analysis of dynamical systems, with computational cost far superior to Monte Carlo simulations. It is a useful tool for control systems analysis because it allows probabilistic description of the effects of uncertainty, especially in systems having nonlinearities and where other techniques, such as Lyapunovís method, may fail. We show that stability of a system can be inferred from the evolution of modal amplitudes, covering nearly the full support of the uncertain parameters with a finite series. By casting uncertain parameters as unknown gains, we show that the separation of stochastic from deterministic elements in the response points to fast iterative design methods for nonlinear control.

End Effect in Short Secondary Linear Induction Motors

2006

James L. Kirtley, Andrew P. Johnson
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One of the reasons linear motors, a technology nearly a century old, have not been adopted for a large number of linear motion applications is that they have historically had poor efficiencies. This is due to the open-ended geometry of a linear motor, and has restricted the progress of linear motor development [1], [2], [3], [4]. The end effect is a direct consequence of this open-ended geometry. This paper will address the issue of whether or not the end effect phenomenon of a short secondary Linear Induction Motor (LIM) could be responsible for any reduction in average thrust and consequently, a reduction in motor efficiency.

Stochastic Analysis of Induction Machines Using Generalized Polynomial Chaos

2006

Pradya Prempraneerach, Timothy McCoy, Franz Hover, M.S. Triantafyllou
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It is well known that parametric and loading uncertainties can have adverse effects on the control of electric machines (Bose 1986). Machines used for ship propulsion, for example, are subject to random loading as a result of the seaway. To date, there have been few studies which can account for these stochastic effects in a comprehensive way. The generalized Polynomial Chaos (gPC)(Ghanem and Spanos 1991), (Lucor, Su and Karniadakis 2004), (Xiu and Karniadakis 2002),(Wan and Karniadakis 2005) is applied to induction machines in this paper. We show that the gPC technique captures the statistics of the response more efficiently than does Monte Carlo simulation.

Multi-Element Generalized Polynomial Chaos: A New Method to Model Uncertainty in Complex Systems

2006

Pradya Prempraneerach, Xiaoliang Wan, George Karniadakis
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Electric Ship Research and Development Consortium

2006

Michael Triantafyllou, Franz Hover, George Em Karniadakis, Jim Kirtley , Steve Leeb
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Electric Ship Education

2006

Chryssostomos Chryssostomidis
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Minimally Intrusive Strategies for Fault Detection and Energy Monitoring

2006

Robert W Cox
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This thesis addresses the need for automated monitoring systems that rely on minimally intrusive sensor arrays. The monitoring techniques employed in this thesis require fewer sensors because they take a different approach to the measurement problem. Specifically, these techniques use the power distribution network in the target system as a power source, a sensor array, and a communications channel. In this “multi-use” approach, the only measurement sources are a set of centrally located electrical transducers (i.e. voltage and current sensors) and a set of remotely located sensors that communicate with a central processing unit via power line modems. In general, these systems determine the status of critical loads or systems using only electrical data. Thus, remotely located sensors are only employed in order to gather information that would be difficult, if not impossible, to obtain electrically. Examples of such quantities include air exchange rates and occupancy levels in individual rooms. This thesis describes the development and application of several critical features of the minimally intrusive monitoring systems described above. First, it presents several modelbased methods that make it possible to use electrical data to detect faults in certain mechanical systems. In particular, two such models are described. The first of these is intended to be applied in systems in which an electromechanical actuator cycles its operation according to the value of some other variable, such as a pressure or a temperature. Examples include compressed air and vacuum systems. The other model is used to diagnose the impending failure of the mechanical coupling through which a motor drives an inertial load such as a pump impeller. This thesis also describes the development of a minimally intrusive airflow monitoring system that uses ozone as a tracer gas. This system fits easily into the “multiuse” framework because it relies on a network of distributed ozone generators and detectors whose operation is coordinated via power line communications. Finally, this thesis also presents and demonstrates a method for detecting the operation of various electrical loads using transient changes in the measured line voltage. This technique makes it possible to use “plug-in” sensors to determine the operating schedule of each of the various loads in a home or commercial facility. All of the techniques and methods described here are demonstrated experimentally.

AGENT-BASED APPROACH TO SPACE ALLOCATION IN GENERAL ARRANGEMENTS

2006

Anthony S. Daniels, Michael G. Parsons
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This paper discusses the formulation and development of an agent-genetic hybrid optimization kernel for the Zone-deck allocation of spaces in a preliminary ship design general arrangements design system.. In this system, design agents representing the interests of the spaces and the Zone-decks are utilized to improve a population of candidate solutions. Their design change requests are accepted or denied by a domain agent if they will improve the overall ship allocation design. In parallel, a design judge agent monitors the population and reseeds dominated or infeasible solutions and a genetic algorithm agent provides periodic stochastic manipulation of the population to improve the algorithm’s global search capabilities. The algorithm is used to optimize the allocation for a 70 space-17 Zone-deck small combatant.

Zonal Ship Design

2006

Norbert H. Doerry
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Modern ships typically have a number of distributed systems. Distributed systems are used because it’s simpler, cheaper, and better to centrally produce a commodity such as electricity or chill water, than to locally produce it with the users of the commodity. For naval warships, in addition to cost, two measures of performance are very important: Survivability and Quality of Service. Survivability relates to the ability of the distributed system, even when potentially damaged by a threat, to support the ship’s ability to continue fulfilling its missions to the degree planned for the particular threat. Quality of Service measures the ability of the distributed systems to support the normal, undamaged operation of its loads. This paper defines a number of key terms, details a number of different zonal architectures, describes the situations where the architectures are best suited and proposes a framework for zonal ship design that promises to satisfy survivability performance requirements and quality of service requirements.

Induction Generator Power Conversion and Control

2006

Steven Englebretson, James Kirtley
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High speed induction generators could operate as an effective primary or reserve source of electric power in a DC system using a power converter to control the generator output, circulate the varying amounts of reactive power between the machine terminals to maintain excitation, and rectify the output power. Frequency control at the stator output terminals is used to adjust the generator real power under a constant or nearly constant drive speed. Reactive power circulation between an ideally balanced three phase generator and a six step converter is examined in detail, comparing two different switching schemes. With three switches conducting simultaneously, reactive power can be transferred directly between phases while a pattern with only two switches conducting at a time uses a DC capacitor to sink and source reactive power to and form all three phases. Steady state simulations demonstrate the system operation.

New Approach to Ungrounded Fault Location in a Three-Phase Underground Distribution System using Combined Neural Networks & Wavelet Analysis

2006

Jamal Moshtagh, R. K. Aggarwal
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This paper presents the results of investigations into a new fault location technique based on a new modified cable model, in the EMTP software. The simulated data is then analysed using advanced signal processing technique based on wavelet analysis to extract useful information from signals and this is then applied to the artificial neural networks (ANNs) for locating ungrounded shunt faults in a practical underground distribution system. The paper concludes by comprehensively evaluation the performance of the technique developed in the case of ungrounded short circuit faults. The results indicate that the fault location technique has an acceptable accuracy under a whole variety of different systems and fault conditions.

Large Eddy Simulation of Crashback in Marine Propellers

2006

Martin Vysohlid, Krishnan Mahesh
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The large eddy simulation methodology is applied to predict the flow around a marine propeller in the forward and crashback modes of operation. A non-dissipative, robust numerical algorithm developed by Mahesh et al. (2004, J. Comput. Phys., 197:215-240) for unstructured grids was extended to include the effect of rotating frame of reference. The thrust and torque coefficients, circumferentially averaged mean velocity and root mean square fluctuation of velocity obtained from the simulation are compared to experimental data and good agreement is observed. The crashback simulations show the presence of a highly unsteady ring-vortex, and irregular low frequency unsteady loads on the propeller.

Dynamic Optimization Using Hermite Chaos

2005

Franz S Hover, Michael Triantafyllou
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The polynomial chaos of Wiener provides a framework for the statistical analysis of dynamical systems, with computational cost far superior to Monte Carlo simulations. We show that the gradient method for dynamic optimization (the Maximum Principle) can be applied in a stochastic sense using Hermite chaos, giving rise to the complete family of optimal trajectories parameterized with a small number of random variables.

Design and Analysis of a Permanent Magnet Generator For Naval Applications

2005

Jonathan E. Rucker, Timothy J. McCoy
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This paper discusses the electrical and magnetic design and analysis of a permanent magnet (PM) generation module for naval applications. Numerous design topics are addressed and several issues are raised about the potential improvements a PM generation system can offer. A proposed 16 MW PM generation module design is presented along with a design methodology. The final design offers significant reductions in both weight and volume. Specifically, it is estimated that the PM generation module has a 7x reduction in volume and a 10x reduction in weight compared to similarly rated wound rotor systems. These reductions can provide flexibility to naval architects since power, weight, and volume are integral parts of the design and construction processes. However, further study is necessary to verify the PM generation modules thermal, structural, and mechanical performance.

Design and Analysis of a Permanent Magnet Generator for Naval Applications (MA Thesis)

2005

Jonathan Rucker
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This paper discusses the electrical and magnetic design and analysis of a permanent magnet generation module for naval applications. Numerous design issues are addressed and several issues are raised about the potential improvements a PM generation system can offer. A proposed 16 MW PM generation module design is presented along with a detailed design methodology. Eighty different machines and power conversion modules are sized, designed, and analyzed with a final design selected. Specifically, sizing and detailed machine design and analysis is performed examining the effects of numerous parameters including number of phases, number of poles, magnetic geometry, machine dimensions, and material types. Analytical models are developed to study rotor losses caused by stator winding time and space harmonics and slot space harmonics. Power electronics and conversion modules to connect the high-speed generator to a DC distribution system are designed and analyzed. In depth simulation of the eighty complete systems is performed using the software programs MATLAB (Version 12.0, Mathworks) and PSIM (Version 6.0, Powersim, Inc.). The 16 MW permanent magnet generation module, consisting of the generator and associated power electronics, provides an excellent alternative to traditional wound rotor machines. The final design offers significant reductions in both weight and volume. Specifically, it is estimated that the PM generation module has a 7x reduction in volume and a 10x reduction in weight compared to similarly rated wound rotor systems. These reductions can provide flexibility to naval architects since power, weight, and volume are integral parts of the design and construction processes. However, further study is necessary to verify the PM generation modules thermal, structural, and mechanical performance.

Investigating the Steady and Unsteady Maneuvering Dynamics of an Azimuthing Podded Propulsor

2005

Jeffrey W. Stettler, Franz Hover, Michael Triantafyllou
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This paper provides highlights of results of a recent investigation completed at the Massachusetts Institute of Technology pertaining to the characterization of the steady and unsteady maneuvering force dynamics associated with an azimuthing podded propulsor. Highlighted results include quasi-steady and unsteady forces, as well as several methods of flow visualization.

Adaptive Maximum Torque Per Amp Control Strategy

2005

Chunki Kwon, Scott D. Sudhoff
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Maximum Torque Per Amp (MTPA) control of induction motor drives seeks to achieve a desired torque with the minimal possible stator current, which is favorable in terms of inverter operation, and nearly optimal in terms of machine efficiency. This work demonstrates that existing MTPA controls perform sub-optimally as temperature varies. An adaptive MTPA control strategy is proposed that always achieves optimal performance regardless of rotor temperature and does so without exhibiting the hunting phenomenon. The proposed control is experimentally shown to (i) accurately achieve the desired torque, and (ii) always satisfy the maximum torque per amp condition.

Synchronous Machine Model With Saturation and Arbitrary Rotor Network Representation

2005

Dionysios C. Aliprantis, Scott D. Sudhoff, Brian T. Kuhn
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This paper addresses equivalent circuit and magnetic saturation issues associated with synchronous machine modeling. In the proposed synchronous machine model, the rotor equivalent circuits are replaced by arbitrary linear networks. This allows for elimination of the equivalent circuit parameter identification procedure since the measured frequency response may be directly embedded into the model. Magnetic saturation is also represented in both the - and -axis. The model is computationally efficient and suitable for dynamic time-domain power system studies.

Design of robust shipboard power automation systems

2005

Edwin L. Zivi
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Emergent power and automation technologies provide new opportunities and challenges for multi-disciplinary ship design. In particular, these dynamically interdependent systems require dependable, fault-tolerant control to efficiently manage limited resources and to respond to casualty conditions. Design of an electric warship engineering and damage control system of systems is considered as an illustrative example. In this context, cost and survivability can be considered as either deterministic or probabilistic independent variables. In the stochastic formulation, design robustness is defined with respect to uncertainties including technology readiness, mission creep, and operational environment.

Solid-State Circuit Breakers and Current Limiters for Medium-Voltage Systems Having Distributed Power Systems

2004

Christoph Meyer, Stefan Schroder, Rik W. De Doncker
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State-of-the-art mechanical circuit breakers in medium-voltage systems allow a safe handling of short-circuits if the short circuit power of the grid is limited. Using delayed turn-off times, the circuit breakers can be coordinated with lower level protection gear. Hence, a high availability of the grid can be guaranteed. However, during a short-circuit a significant voltage sag can be noticed locally in the medium-voltage grid. Sensitive loads such as computers will fail even if the voltage returns within a few seconds. A semiconductor circuit breaker, however, is able to switch fast enough to keep voltage disturbance within acceptable limits. The optimization and selection of power electronic switch topologies is critical. In this paper, different semiconductors are briefly compared considering the requirements of a solid-state switch integrated into a 20-kV medium-voltage grid. Based on these semiconductor characteristics, various switch topologies are developed, which are compared under technical and economical aspects. It is shown that solid-state circuit breakers offer significant advantages when compared to present solutions and can be used in today's medium-voltage power systems.

Comparison of Wall Boundary Conditions for Numerical Viscous Free Surface Flow Simulation

2004

I. Robertson, S. J. Sherwin, J.M. R. Graham
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A spectral/hp element code, incorporating a velocity-pressure formulation, is used to simulate free surface flows. Nonlinear pressure and velocity boundary conditions are applied on the moving free surface, the tracking of which is facilitated by the implementation of an Arbitrary Lagrangian Eulerian (ALE) formulation. The derived algorithm is validated by comparing the numerical results evaluated here with an analytical method which predicts the damping of a freely sloshing, viscous fluid for a range of Reynolds number: 3[less-than-or-equals, slant]Re[less-than-or-equals, slant]3x105 where Re=(gd)1/2d/[nu] and g, d and [nu] are gravity, depth of fluid and kinematic viscosity, respectively. The free surface wall contact point is investigated and a number of approximations to overcome the contradiction of a moving contact point and the wall no-slip condition are presented. The numerical procedure which utilizes these approximations is tested against a linear, analytical method which predicts viscous diffusion in the vicinity of the containing walls for a freely sloshing fluid. It is found that the numerical results using the various formulated boundary conditions converge as the Reynolds number increases.

Comparison of Analytical and Numerical Approaches for Determining Failure of Ring-Stiffened Cylindrical Shells (MA Thesis)

2003

Michael W. Temme
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The thesis compares the analytical solution, two marine classification society design rules, and numerical analysis against experimental results for predicting the failure modes (general instability, axisymmetric buckling, and asymmetric collapse of the shell) and failure pressures of ring-stiffened cylindrical shells. The analytical solution is first summarized based on several sources. Design rules for the classification societies are then presented with brief explanations for each one. The design rules used are: American Petroleum Institute (Bulletin on Stability Design of Cylindrical Shells, API Bulletin 2U, Second Edition, October 2000) and Det Norske Veritas (Buckling Strength of Shells, October 2002). The numerical analysis was performed using the software package, Method For Analysis Evaluation and Structural Optimization (MAESTRO™, version 8.5, Proteus Engineering). The United States Navy Naval Sea Systems Command, Submarine Structural Integrity Division supplied experimental data for four test cylinders that covered the failure modes and allowed comparison between experimental and analytical / numerical results. The comparison of experimental to predicted data found the design rules and numerical solution performed adequately in predicting asymmetric buckling and general instability failure modes, but the predictions for failure pressure were unsatisfactory. The design rules were overly conservative in their predictions of failure pressure due to the semi-empirical solutions used in the rules. The numerical solution was only slightly better for the same failure pressure predictions. The results indicate the predicted failure pressure for a cylinder is closely tied to the size and dimensions of the cylinders used for determining the empirical solutions. These results should be further explored to determine causes and corrections.

DC Bus Voltage Control for a Distributed Power System

2003

Per Karlsson
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This paper addresses voltage control of distributed dc power systems. DC power systems have been discussed as a result of the introduction of renewable, small-scale power generation units. Also, telecommunication power systems featuring UPS properties might benefit from a broader introduction of dc power systems. Droop control is utilized to distribute the load between the source converters. In order to make the loading of the source converters equal, in per unit, the voltage control algorithm for each converter has to be designed to act similar. The dc side capacitor of each converter, needed for filtering, is also determined as a consequence. The root locus is investigated for varying dc bus impedance. It is found that the risk of entering converter over-modulation is a stronger limitation than stability, at least for reasonable dc bus cable parameters. The stationary and dynamic properties during load variations are also investigated.

Voltage Control and Load Sharing in DC Distribution Systems

2003

Per Karlsson, Jorgen Svensson
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This paper addresses voltage control and load sharing in DC distribution systems. At present, DC distribution systems are utilised in, for example, telecommunication systems. Future applications could also involve distributed power systems based on renewable energy sources. The dynamic and stationary properties of voltage droop control and its load sharing abilities are investigated. The DC bus voltage droop controller gain is selected so that the loading of each source converter is equal in per unit. Both experimental and simulation results verify the operation. Experimental results regarding fault detection in DC distribution systems are also presented.

Effects of a Fast Switching Fault Current Limiter on Distance Protection

2003

Shawn Henry, Thomas Baldwin, Michael Steurer
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This work investigates the impact of a fast switching fault current limiter (FCL) on a distance protection scheme. The FCL is modeled utilizing GTOs to insert a resistive impedance in and out of the protected line. The examination is performed by analyzing the transient response of distance relay elements with and without the presence of the FCL in a protective scheme. Relay selectivity is explored while placing the FCL in front and behind the relay element. Furthermore, problems such as multiple tripping and nuisance tripping are investigated and solutions to these problems are addressed.

Standard Submarine Model: A Survey of Static Hydrodynamic Experiments and Semiempirical Predictions

2003

M. Mackay
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This report describes comparison between measurements of static hydrodynamic loads on the Standard Submarine Model in a number of different test facilities, and comparison between selected experimental data and predictions from the DSSP20 manoeuvering simulation code. The experiments constitute a substantial database for code development and validation. Differences between data from various facilities are in general not very great. Agreement with the predictions is generally satisfactory within a modest range of incidence, i.e., angles below 20 to 30 degrees, although some significant deviations are observed outside this range.

Novel Hybrid Current-Limiting Circuit Breaker for Medium Voltage: Principle and Test Results

2003

Michael Steurer, Klaus Frohlich, Walter Holaus, Kurt Kaltenegger
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Although many attempts have been made to design a fault current-limiting circuit breaker (FCLCB) for medium voltage electric power systems, no economically attractive solution has been achieved so far. A novel concept for an F CLCB is introduced based on a hybrid arrangement of semiconductors, temperature-dependent resistors, and a newly developed fast-opening mechanical switch. The latter utilizes one part of an electrodynamic repulsion drive, which is concurrent with the moving double contact system. Laboratory tests as well as computer simulations of the complete FCLCB verify as an example the feasibility for the goal ratings 12 kV and 2/20 kA (single phase). A cost analysis shows the FCLCB to be more expensive than a conventional generator circuit breaker but to be in the price range of the Is-limiter and below the costs of superconducting FCL principles. It is concluded that the method provides the basis for further commercial product development.

DC Distributed Power Systems Analysis, Design and Control for a Renewable Energy System

2002

Per Karlsson
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Renewable energy systems are likely to become wide spread in the future due to environmental demands. As a consequence of the dispersed nature of renewable energy systems, this implies that there will be a distributed generation of electric power. Since most of the distributed electrical energy sources do not provide their electric power at line frequency and voltage, a DC bus is a useful common connection for several such sources. Due to the differences in output voltage among the sources, depending on both the type of source and their actual operating point, the sources are connected to the DC power system via power electronic converters. The intention behind the presented work is not to replace the existing AC power system, but to include local DC power systems. The AC and DC power systems are connected at some points in the network. The renewable energy sources are weak compared to the present hydro power and nuclear power plants, resulting in a need of power conditioning before the renewable energy is fed to the transmission lines. The benefit of such an approach is that power conditioning is applied on a central level, i.e. at the interface between the AC and DC power systems. The thesis starts with an overview of related work. Present DC transmission systems are discussed and investigated in simulations. Then, different methods for load sharing and voltage control are discussed. Especially, the voltage droop control scheme is examined thoroughly. Since the droop control method does not require any high-speed communication between sources and loads, this is considered the most suitable for DC distributed power systems. The voltage feed back design of the controller also results in a specification of the DC bus capacitors (equivalents to DC link capacitors of single converters) needed for filtering. If the converters in the DC distribution system are equipped with capacitors selected from this design criterion and if the DC bus impedance is neglected, the source converters share the total load equally in per unit. The same DC distribution bus configuration is studied in a wind power application. Especially the dynamic properties of load-source interactions are highlighted. They are interesting since the sources are considered weak for a distributed power system. This is illustrated with simulations where the power is fed from wind turbines only and constant power loads are controlled at the same time as the DC bus voltage level. The wind power generators are modeled as permanent-magnet synchronous machines. The controller needed for the machines, including position estimation and field weakening, is discussed. To control the DC bus voltage, the available wind power must be higher than the power consumed by the loads and the excess power removed by pitch angle control. Pitch angle control is a comparably slow process and, therefore, the DC bus voltage controller must handle the transient power distribution. Personal safety and prevention of property damage are important factors of conventional AC power systems. For the investigated DC power system this is maybe even more important due to the fact that the star point of the sources and loads is left ungrounded or grounded through high impedance. The difficulty of detecting ground faults arises from the fact that the AC sources and loads are ungrounded or have high impedance to ground in order to effectively block zero-sequence currents flowing between the AC systems. A grounding scheme for the DC distribution system together with algorithms for detection of ground faults, are presented. The proposed method detects ground faults on both the AC and DC sides and is extended to cover short circuit faults with a minor work effort. Two schemes for high voltage interconnection of DC systems are studied. One of them provides galvanic isolation, which is an advantage since elevated voltage might appear in the DC systems otherwise, in the case of a ground fault in the high voltage interconnection. Experimental verifications follow the theoretical investigations introduced above. First, dynamic properties are studied and the behaviour predicted from theoretical analysis and simulations is verified. Then, load sharing is investigated. Also in this investigation, the experimental results agree with the simulated.

QUASI-STEADY MODEL EXPERIMENTS ON HYBRID PROPULSION ARRANGEMENTS

2002

Jan Holtrop, Patrick Hooijmans
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Several past ITTC committees dealing with powering performance and propulsors have advocated the load-variation test as a valuable addition to the more usual speed-variation test. This loadvariation test is even essential in complex propulsors and it can certainly not be dispensed with when hybrid propulsion concepts are studied by model experiments. At MARIN the load-variation test for one test speed has become a standard addition to every propulsion experiment and, indeed, the information about the effects of the varying load is analysed to enhance consistency and accuracy. At MARIN it was investigated whether the usual test procedure could be simplified and the loadvariation test can be fully dispensed with by carrying out propulsion experiments in a quasi-steady manner. In the quasi-steady method described here, a gradual variation of the rotative speed of the propeller(s) is imposed, while the forward speed of the ship model is kept constant. Thus, the load of the propellers continuously changes during the measurement run.

Extrapolation of Propulsion Tests for Ships with Appendages and Complex Propulsors

2001

Jan Holtrop
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Prediction of ship powering is traditionally based on the results of model experiments. This paper covers the extrapolation of model test results for ships that may have a multitude of appendages and one or more complex propulsors. The major differences from conventional extrapolation methods are the application of the scale effect corrections to the model propulsion test, the treatment of the appendages and acknowledging the effects of the propeller load on the propulsion parameters. The last feature is considered essential to successfully handle complex propulsors with both rotating and passive components.

Accurate Four-Quadrant Nonlinear Dynamical Model for Marine Thrusters: Theory and Experimental Validation

2000

Ralf Bachmayer, Louis L. Whitcomb, Mark A. Grosenbaugh
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This paper reports two specific improvements in the finite-dimensional nonlinear dynamical modeling of marine thrusters. Previously reported four-quadrant models have employed thin airfoil theory considering only axial fluid flow and using sinusoidal lift/drag curves. First, we present a thruster model incorporating the effects of rotational fluid velocity and inertia on thruster response. Second, we report a novel method for experimentally determining nonsinusoidal lift/drag curves. The model parameters are identified using experimental thruster data (force, torque, and fluid velocity). The models are evaluated by comparing experimental performance data with numerical model simulations. The data indicates that thruster models incorporating both reported enhancements provide superior accuracy in both transient and steady-state responses.

LVDC Industrial Power Distribution System Without Central Control Unit

2000

Tang Weizhong, R.H. Lasseter
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This paper develops a scheme to control parallel connected, multiterminal dc power distribution system without the need of central control unit for fast communication. The described scheme utilizes superconductors on the dc bus and incorporates UPS properties with the ability to supply large passive loads than conventional UPS'S. A five terminal, mesh connected study system is used to demonstrate the basic characteristics of dc power distribution system such as the ability to ride through an ac system outrage. In the paper a simulation model of the study system is developed and the simulation results show that the proposed dc power distribution system has a high power quality performance.

Development of a Hybrid Agent-Genetic Algorithm Approach to General Arrangements

2000

Anthony S. Daniels, Michael G. Parsons
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The continuing development of an agent-genetic algorithm hybrid optimization kernel for the allocation of spaces to Zone-decks in a preliminary ship general arrangements design system is presented. In this system, design agents representing the interests of the spaces and the Zone-decks are utilized to propose possible improvements to a population of candidate solutions. Their design change requests are accepted or denied by a domain agent if they will improve the overall ship space allocation design. In parallel, a design judge agent monitors the population and reseeds dominated or infeasible solutions and a genetic algorithm agent provides periodic stochastic manipulation of the population to improve the algorithm’s global search capabilities. The algorithm is used to optimize the Zone-deck allocation of spaces for a Notional Corvette-sized vessel.

Military Handbook: Electronic Reliability Design Handbook

1998

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Coiflet-Type Wavelets::Theory, Design, and Applications

1998

Dong Wei
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During the last decade, the explosively developing wavelet theory has proven to be a powerful mathematical tool for signal analysis and synthesis and has found a wide range of successful applications in the area of digital signal processing (DSP). Compared to their counterparts in the Fourier realm, wavelet techniques permit significantly more flexibility in system design for many applications such as multirate filtering, sampling and interpolation, signal modeling and approximation, noise reduction, signal enhancement, feature extraction, and image data compression. Most classical wavelet systems have been constructed from a primarily mathematical point of view, and they are fundamentally suitable for representing continuous-domain functions rather than discrete-domain data. From a discrete-time or DSP perspective, we develop new wavelet systems. This dissertation focuses on the theory, design, and applications of several novel classes of one-dimensional and multi-dimensional Coiflet-type vii wavelet systems. In particular, we propose a novel generalized Coifman criterion for designing high-performance wavelet systems, which emphasizes the vanishing moments of both wavelets and scaling functions. The resulting new wavelet systems are appropriate for representing discrete-domain data and enjoy a number of interesting and useful properties such as - sparse representations for smooth signals, - interpolating scaling functions, - linear phase filtterbanks, and - dyadic fractional filter coefficients, which are promising in solving a large variety of DSP problems. We show that some of the new wavelet systems achieve superior performance (e.g., better rate-distortion performance, better perceptual quality, and lower computational complexity) over the state-of-the-art ones in the field of image coding.

Integrated Electrical Power Supply System for Propulsion and Service Control

1997

William J. Levedahl
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Engine driven turbines respectively drive separate propulsion and service alternators to supply power to propulsion motors and service equipment on naval combat ships through propulsion and service controls. Rechargeable batteries are connected through the service controls to the service alternators and to service loads through dc bus lines. The propulsion controls interconnect:t the propulsion motors with the propulsion alternators to which the electrically operated weapons are also collected through rectifiers and a pulse forming network.

Shipboard Controls of the Future

1997

John V. Amy, Norbert H. Doerry, Timothy J. McCoy, Edwin L. Zivi
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Recent advances in computer networking and control system technologies present an opportunity to improve the capability of naval shipboard control systems. Most existing digital machinery control systems merely replace one-for-one their analog predecessors. These recent advances motivate rethinking the basic role and architecture of shipboard controls. Traditional machinery system control has remained largely separate from combat systems and other ship information systems. Existing machinery control systems have concentrated on four functions: machinery status, control, system stability, and fault response. To implement these functions, custom systems have been designed, built and debugged for each class of ship. This lack of commonality has been expensive in terms of development costs, maintenance costs over the lifetime of the ship, and also the unrealized benefits stemming from prohibitive costs of adapting machinery controls to take advantage of emerging technologies. This paper proposes a new paradigm for developing a shipboard control system based upon a functional decomposition of ships' missions that leads to defining technology independent interface standards. Multiple vendors may be able to independently develop control system hardware and software elements adhering to such interface standards without a priori knowledge of a particular ship application, leading to the ability to develop a total ship control system with low risk by integrating proven hardware and software elements to meet specific ship design requirements. With this new concept, other functions not normally associated with machinery controls are feasible: spontaneous reconfiguration after a damage event, integrated training, condition based maintenance planning, data archiving, operator assistance, and configuration management. This new approach may also allow for the integration of machinery controls into a total ship control system with seamless support far combat systems. This new shipboard control paradigm promises to speed control system development, improve performance, facilitate maintenance and modernization, and lead to lower life cycle costs.

Improved Methodology for Sizing of Naval Electrical Power Plants

1993

James J. McGlothin
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Electrical power plants onboard ships of the United States Navy have traditionally been sized according to empirical methods. These methods have resulted in satisfactory plants but have not been updated to reflect recent improvements in equipment and analysis methods. Developing technologies under consideration for future ships, particularly integrated electric propulsion with propulsion derived ships service electrical power, will bring significantly different demands f6r electrical power. There is very little recent design experience to fall back on when designing.a ship employing such technologies. In addition, current fiscal restraints demand that excess equipment and capacity be severely restricted in order to minimize procurement costs, manning, and maintenance costs. A methodology is proposed to evaluate electric plant configurations (i.e. number and sizes of generating units) in terms of the probability that the required loads can be supplied. The alternatives can ten be compared in terms of cost, weight, number of units, and total installed capacity to determine which is most cost effective. The methodology has been coded into a program which can be used to easily do the system comparisons. Several shipboard systems are analyzed to demonstrate the usefulness of the program.

Combustion Turbine Dynamic Model Validation from Tests

1993

L. N. Hannett, Afzal Khan
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Governor models can be an important variable affecting the dynamic performance of electrical power systems. One example is the Alaskan Railbelt system whose major source of generation is from combustion turbines. Detailed dynamic simulation models have been proposed for two types of governor controllers. A field test was conducted to derive model parameters. The models derived from field test recordings and data were compared in simulation cases with typical models that were used in earlier studies. Results from the simulation cases revealed that the typical models were more optimistic.

Composite System Analysis of Advanced Shipboard Electrical Power Distribution Systems

1992

Clifford Whitcomb
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Survivability improvement techniques such as equipment separation, redundancy, and arrangement form an integral part of the ship design strategy. The development of tools which can perform assessments of survivability features along with the feasibility, benefits, and costs of such features is required. The ability to evaluate systems in the early or conceptual stages of design is most important to provide the highest potential payoff. A methodology is proposed to perform survivability analyses of composite naval shipboard electrical power distribution systems. The methodology allows the system designer to quantify survivability of various system arrangements, architectures, and control rules. The methodology is coded as an additional capability to an existing system reliability and availability analysis program. The additional analysis sections provide new capabilities for the specific investigation of electric distribution system design alternatives. A method to quantify incremental acquisition and combat effectiveness costs of providing improved survivability is provided. Reliability and availability analysis capabilities are presented. A conceptual naval shipboard electrical power distribution systems is analyzed to demonstrate the techniques employed. For the purposes of this thesis, the data input is specific for electrical distribution systems, but any distributed, interconnected system whether it is an electrical, mechanical, or fluid system could be analyzed with this program.

Advanced Numerical Methods for Simulating Nonlinear Multirate Lumped Parameter Models

1991

Norbert H. Doerry
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Naval shipboard electric power systems are transitioning from the relatively simple distribution of ship service electric power to extremely complex integrated electric drive (IED) systems. The optimal design of warships employing lED is presently hampered by the lack of existing simulation computer tools for analyzing the highly coupled and controlled electro-mechanical systems characteristic of IED. As a first step in the development of a viable computer simulation tool, the numerical algorithm testing program WAVESIM was created.) The key contributions of WAVESIM are the systematic treatment of waveforms as an abstract data type, the development of the terminal description of devices, and the use of structural jacobians in system reduction. WAVESIM represents variables by waveforms consisting of a vector of coefficients and a waveform type code indicating how the coefficients should be interpreted. The principal advantage of using waveforms over conventional discrete point methods is the avoidance of unstable integration techniques since for most waveform types, integration and differentiation are linear matrix operations. Devices are described in WAVESIM by relationships between terminal interface variables. WAVESIM recognizes two types of terminals: normal terminals having both potential and flow variables, and information terminals having only a potential variable. In this manner, WAVESIM can simulate processes involving both energy transfer and control signals. WAVESIM extends the structural jacobian matrix concept to reflect the properties of the dependence of system equations on system variables. The system structural jacobian matrix is constructed from the constitutive device structural jacobian matrices and is used to identify a sequence of smaller blocks when can be solved consecutively for all the system variables. To demonstrate and verify the capabilities of WAVESIM, several simulations were conducted. In all simulations, WAVESIM provide results matching data generated by other simulation methods.

Composite System Stability Methods Applied to Advanced Shipboard Electric Power Systems

1990

John Victor Amy, Jr.
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Large increases in the complexity of shipboard electric loads as well as development of electric drive, integrated electric drive and pulsed power systems make manifest the present and future importance of naval electric power systems. The most crucial attribute of these systems is their ability to fulfill their function in the presence of "large-signal" perturbations. Fundamental differences between shipboard and commercial electric power system''s make all but the most general nonlinear, "large-signal" stability analyses inappropriate for the design and assessment of naval electric power systems. The tightly coupled and compact nature of shipboard systems are best accommodated by composite system stability analyses. Composite system methods, based upon Lyapunov's direct method, require that each component's stability be represented by a Lyapunov function. A new Lyapunov function which is based upon coenergy is developed for 3-phase synchronous machines. This use of coenergy is generalizable to all electromechanical energy conversion devices. The coenergy-based Lyapunov function is implemented as a "stability organ" which generates waveforms at information terminals of a "device object" in the object oriented simulation environment of WAVESIM. Single generator simulation results are used to acquire a measure of the "over sufficiency" of the coenergy-based L'yapunov function. Some means of combinulg the components' Lyapunov fullctions is necessary with composite system stability criterions. To provide tile largest stability re,sion in a Lyapunov function convective derivative space, thereby reducing Hover sufficlency", a "titllevariant weighted-sum" composite systcln criteriol1 is developed. This criterion is inlplemented as a "stability denlon" "device objecttl within the WAVESITvi ellvirollllleKlt. TIle "stability demon" is tested tllfougl1 RLC circuit simulations alld a two-generator Sitllulation. The output of the "stability delnon" is suitable for use witlliJl illl overall syst.enl stabilising controller.

Development of a high current HVDC circuit breaker with fast fault clearing capability

1988

B. Pauli, G. Mauthe, E. Ruoss, G. Ecklin, J. Porter, J. Vithayathil
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Recent years have seen rapid growth in direct current transmission. This growth increases the need and scope of application for a high voltage direct current circuit breaker. Significant improvements have been made in a previously developed 500 kV, 2000 a HVDC circuit breaker. These improvements have increased the current interrupting capabilities to 4000 A DC and more and have decreased the fault clearing time to the order of AC breakers of similar voltage ratings. The result is a HVDC circuit breaker that is built using well-proven AC power system components. It is modular in design so as to be suitable for a wide range of system voltages and energy levels.

Comparative Study of Various Electric Propulsion Systems and their Impact on a Nominal Ship Design

1987

James C. Davis,
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Synchronous, permanent magnet, and induction machines are modeled using computer programs. The computer programs incorporate an optimization algorithm which converges on lowest weight, volume, and inefficiency. Machine designs for high and low rpms are performed, with a varying number of pole-pairs. The machine designs are analyzed to find the optimum combination of generator and motor for inclusion in a naval ship propulsion system. Three ships are used for the system study, a baseline mechanical transmission ship, a ship retaining the same subdivision as the baseline but with the electric machinery, and an electric transmission ship with subdivision and machinery box arrangement chosen to benefit from the inherent arrangeability of electric transmissions. wo generator/motor combinations are used in the final ship analysis/ Both employ a 3600 rpm, six-pole synchronous generator, which turns at the shaft speed of the prime mover. One combination uses a 180 rpm, direct-drive, 16- pole synchronous motor, and the other uses an 1800 rpm, geared, 8-pole synchronous motor. Power converters are used in both combinations to control motor speed. The geared combination in the rearranged ship demonstrated the best endurance speed efficiency, reducing the endurance fuel load by 18%, while maintaining the maximum and sustained speed of the baseline ship. The savings in ship volume translated to an additional twenty Tomahawk missile cells in the rearranged ship. When the fuel load was held at the tonnage of the baseline ship, endurance range increased as much as 25%. Permanent magnet machines were not competitive in this study due to their high weight and volume, even though their individual machine efficiency was the highest of all types. Induction machines were not used as propulsion generators because of the inherent difficulties in control. The induction machine motor candidates were not competitive because of off-design-point inefficiency.

Statistical Re-Analysis of Resistance and Propulsion Data

1984

Jan Holtrop
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In a recent publication a power prediction method was presented which was based on a regression analysis of random model and full-scale test data. For several combinations of main dimensions and form coefficients the method had been adjusted to test results obtained in some specific cases. In spite of these adaptations the accuracy of the method was found to be insufficient for some classes of ships. Especially for high speed craft at Froude numbers above 0.5 the power predictions were often wrong. With the objective to improve the method the data sample was extended covering wider ranges of the parameters of interest. In this extension of the data sample the published results of the Series 64 hull forms have been included. The regression analyses were now based on the results of tests on 334 models. Beside these analyses of resistance and propulsion properties a method was devised by which the influence of the propeller cavitation could be taken in account. In addition some formulae are given by which the effect of a partial propeller submergence can tentatively by estimated. These formulae have been derived in a study carried out in a MARIN Co-operative Research programme. Permission to publish these results is gratefully acknowledged.

Approximate Power Prediction Method

1982

Jan Holtrop, G. G. J. Mennen
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In an earlier publication, a statistical method was presented for the determination of the required propulsive power at the initial design stage of a ship. This method was developed through a regression analysis of random model experiments and full-scale data, available at the Netherlands Ship Model Basin. Because the accuracy of the method was reported to he insufficient when unconventional combinations of main parameters were used, an attempt is made in the present article to extend the method by adjusting the original numerical prediction model to test data obtained in some specific cases. This adaptation of the method has resulted in a set of prediction formulae with a wider range of application. Nevertheless, it is pointed out that the given modifications have a tentative character only, because the adjustments are based on a small number of experiments. In any case, the application is limited to hull forms resembling the average ship described by the main dimensions and form coefficients used in the method. The extension of the method was focused on improving the power prediction for high-block ships with low L/B ratios, and for slender naval ships with complex appendage arrangements and immersed transom sterns.

Alternative Propulsion Methods for Surface Combatants and Amphibious Warfare Ships

1981

James S. Webster, Howard Fireman, Dillon A. Allen, Adrian J. Mackenna, John C. Hootman
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The US Navy has been studying the technical and cost impacts associated with the availability and cost of fossil fuel contrasted with nuclear energy alternatives for surface combatants and amphibious warfare ships. Over the past two years these efforts have grown in maturity to examine the tactical and strategic implications of our Navy’s dependence on fossil fuels from technical, economic, and military perspectives. This paper describes the NAVSEA evaluation of alternative propulsion methods in Small, Medium, and Large Surface Combatants performed during FY2005 in response to Chief of Naval Operations Guidance, and the efforts conducted during FY2006 directed by Public Law that added Amphibious Warfare Ships. Ship concepts were developed and analyzed in terms of acquisition cost, life-cycle cost, and operational effectiveness. Power and propulsion technologies including nuclear power, gas turbines, diesel engines, mechanical power transmission systems, hybrid power transmission systems, integrated power transmission systems, combined power plants (e.g., diesel and gas turbine), and various propulsor systems. Operational effectiveness in warfare, mobility and vulnerability areas areevaluated for alternative power and propulsion systems and associated architectures in non-program-of-record small (~7,500 to ~12,000 metric ton) and medium (~21,000 to ~26,000-metric ton) surface combatants and in amphibious warfare (~34,000 to ~38,000-metric tons) ship concept designs. The techniques and models used in the studies are discussed, examples provided, and results presented. These results include a discussion of viable near term alternative power and propulsion system technologies and architectures, breakeven cost of oil (where life cycle costs of nuclear and fossil powered ship concepts are equivalent), and correlation of alternative architectures with operational benefits.

Statistical Data for the Extrapolation of Model Performance Tests

1978

Jan Holtrop
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In view of an adequate extrapolation of model performance test results and statistical analysis of results of towing tank experiments and full-size speed trials has been made. This analysis covers not only the derivation of the correlation factors that account for the scale effects that are present in the model-test results, but also the separation of the resistance into components of different origin with emphasis on the determination of the form factor from either low-speed resistance measurements or from a statistical formula. Some of these results have been published in a previous paper. In that article, however, the extrapolation method has not been described in detail.

Statistical Analysis of Performance Test Results

1977

Jan Holtrop
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A statistical evaluation of model and trial test results, selected from the archives of the Netherlands Ship Model Basin, was carried out using multiple regression analysis methods. The objective of this study was to develop a numerical description of the ship's resistance, the propulsion properties and the scale effects between the models and the full size. The most important applications of the obtained results are the determination of the required propulsive power without doing specific model tests and further the refinement of the extrapolation method by which model test results are scaled up. The evaluation was performed by applying multiple regression analysis to the results of 1707 resistance measurements, 1287 propulsion measurements carried out with 147 ship models and the results of 82 trial measurements made on board 46 new ships.

Seakeeping standard series for cruiser-stern ships

1975

Theodore A. Loukakis, Chryssostomos Chryssostomidis
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The ranges of the principal characteristics of the Series 60 were extended to cover present shipbuilding practices. The seakeeping performance in head seas of 72 hull forms from the Extended Series 60 was evaluated theoretically. The results are presented in tabular form as a function of the principal characteristics of the ship, the Froude number, and the seaway. The Seakeeping Tables include: heaving motion at amidships; pitching motion; moment; added resistance; acceleration at stations 0, 5, 10, 15, and 20; relative motion at stations 1, 2, 3, 4, and 20; and relative velocity at stations 1, 2, 3, 4, and 20. The results of the Seakeeping Tables can be interpolated for the prediction of the seakeeping performance of cruiser- stern ships not necessarily with Series 60 hull forms. Additional seakeeping information for extreme values, wetness, keel emergence, slamming, and propeller racing can be obtained from the results of the Seakeeping Tables.

DESIGN, CAVITATION PERFORMANCE, AND OPEN-WATER PERFORMANCE OF A SERIES OF RESEARCH SKEWED PROPELLERS

1971

Robert J. Boswell
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Cavitation tunnel and open-water results are presented for a series of skewed propellers that were designed by lifting-surface methods. The four model propellers had maximum projected skew at the blade tip equal to 0, 36, 72, and 108 deg. The results showed that the cavitation-free bucket becomes substantially wider with increasing skew: however, there wa:: some crossover in the inception of back cavitation and tip vortex cavitation among the three skewed designs near design advance coefficient. Near the self-propulsion condition, the propeller with 3V deg of skew had the highest cavitation inception speed. Forward opcnwater propulsion performance including lift effectiveness and performance breakdown due to cavitation were substantially the same for the four propellers. Al! four propellers developed the design thrust loading coefficient within 1 a)erc-nt of design rprr, ir open water. At constant power and thrust loading coefficients, the backing speed decreased slightly with incroasin- a skew (respective reductions of 1.5, 8.0, and 12.5 percent for 36, 72, and 108 deg of skew).