The electric power systems in U.S. Navy ships supply energy to sophisticated systems for weapons, communications, navigation and operation. The reliability and survivability of a Shipboard Power System (SPS) are critical to the mission of a Navy ship, especially under battle conditions. When a weapon hits the ship in the event of battle, it can cause severe damage to the electrical systems on the ship. Researchers in the Power System Automation Laboratory (PSAL) at Texas A&M University have developed methods for performing reconfiguration of SPS before or after a weapon hit to reduce the damage to SPS. Reconfiguration operations change the topology of an SPS. When a system is stressed, these topology changes and induced dynamics of equipment due to reconfiguration might cause voltage instability, such as progressive voltage decreases or voltage oscillations. SPS stability thus should be assessed to ensure the stable operation of a system during reconfiguration. In this dissertation, time frames of SPS dynamics are presented. Stability problems during SPS reconfiguration are classified as long-term stability problems. Since angle stability is strongly maintained in SPS, voltage stability is studied in this dissertation for SPS stability during reconfiguration. A test SPS computer model, whose simulation results were used for stability studies, is presented in this dissertation. The model used a new generalized methodology for modeling and simulating ungrounded stiffly grounded power systems. This dissertation presents two new indices, a static voltage stability index (SVSILji) and a dynamic voltage stability index (DVSI), for assessing the voltage stability in static and dynamic analysis. SVSILji assesses system stability by all lines in SPS. DVSI detects local bifurcations in SPS. SVSILji was found to be a better index in comparison with some indices in the literature for a study on a two-bus power system. Also, results of DVSI were similar to the results of conventional bifurcation analysis software when applied to a small power system. Using SVSILji and DVSI on the test SPS computer model, three of four factors affection voltage stability during SPS reconfiguration were verified. During reconfiguration, SVSILji and DVSI are used together to assess SPS stability.

The electric power systems in U.S. Navy ships supply energy to sophisticated systems for weapons, communications, navigation and operation. The reliability and survivability of the Shipboard Power System (SPS) are critical to the mission of a surface combatant ship, especially under battle conditions. In the event of battle, various weapons might attack a ship. When a weapon hits the ship it can cause severe damage to the electrical system on the ship. This damage can lead to de-energization of critical loads on a ship that can eventually decrease a ship’s ability to survive the attack. It is very important, therefore, to maintain availability of energy to the connected loads that keep the power systems operational. Technology exists that enables the detection of an incoming weapon and prediction of the geographic area where the incoming weapon will hit the ship. This information can then be used to take reconfiguration actions before the actual hit so that the actual damage caused by the weapon hit is reduced. The Power System Automation Lab (PSAL) has proposed a unique concept called "Predictive Reconfiguration" which refers to performing reconfiguration of a ship’s power system before a weapon hit to reduce the potential damage to the electrical system caused by the impending weapon hit. The concept also includes reconfiguring the electrical system to restore power to as much of the healthy system as possible after the weapon hit. This dissertation presents a new methodology for Predictive Reconfiguration of a Shipboard Power System (SPS). This probabilistic approach includes a method to assess the damage that will be caused by a weapon hit. This method calculates the expected probability of damage for each electrical component on the ship. Also a heuristic method is included, which uses the expected probability of damage to determine reconfiguration steps to reconfigure the ship’s electrical network to reduce the damage caused by a weapon hit. This dissertation also presents a modified approach for performing a reconfiguration for restoration after the weapon hits the system. In this modified approach, an expert system based restoration method restores power to loads de-energized due to the weapon hit. These de-energized loads are restored in a priority order. The methods were implemented using multi-agent technology. A test SPS model based on the electrical layout of a non-nuclear surface combatant ship was presented. Complex scenarios representing electrical casualties caused due to a weapon hit, on the test SPS model, were presented. The results of the Predictive Reconfiguration methodology for complex scenarios were presented to illustrate the effectiveness of the developed methodology.

The electric power systems in U.S. Navy ships supply energy to sophisticated systems for weapons, communications, navigation and operation. The reliability and survivability of the Shipboard Power System (SPS) are critical to the mission of a surface combatant ship, especially under battle conditions. In the event of battle, various weapons might attack a ship. When a weapon hits the ship it can cause severe damage to the electrical system on the ship. This damage can lead to de-energization of critical loads on a ship that can eventually decrease a ship’s ability to survive the attack. It is very important, therefore, to maintain availability of energy to the connected loads that keep the power systems operational. Technology exists that enables the detection of an incoming weapon and prediction of the geographic area where the incoming weapon will hit the ship. This information can then be used to take reconfiguration actions before the actual hit so that the actual damage caused by the weapon hit is reduced. The Power System Automation Lab (PSAL) has proposed a unique concept called "Predictive Reconfiguration" which refers to performing reconfiguration of a ship’s power system before a weapon hit to reduce the potential damage to the electrical system caused by the impending weapon hit. The concept also includes reconfiguring the electrical system to restore power to as much of the healthy system as possible after the weapon hit. This dissertation presents a new methodology for Predictive Reconfiguration of a Shipboard Power System (SPS). This probabilistic approach includes a method to assess the damage that will be caused by a weapon hit. This method calculates the expected probability of damage for each electrical component on the ship. Also a heuristic method is included, which uses the expected probability of damage to determine reconfiguration steps to reconfigure the ship’s electrical network to reduce the damage caused by a weapon hit. This dissertation also presents a modified approach for performing a reconfiguration for restoration after the weapon hits the system. In this modified approach, an expert system based restoration method restores power to loads de-energized due to the weapon hit. These de-energized loads are restored in a priority order. The methods were implemented using multi-agent technology. A test SPS model based on the electrical layout of a non-nuclear surface combatant ship was presented. Complex scenarios representing electrical casualties caused due to a weapon hit, on the test SPS model, were presented. The results of the Predictive Reconfiguration methodology for complex scenarios were presented to illustrate the effectiveness of the developed methodology.

Future all-electric warships with an integrated power system (IPS) are capable of unlocking large amounts of power dedicated to propulsion and redirecting this power for service loads, weapon loads, and other loads. The IPS for all-electric ships combines the power generation system, electric propulsion system, power distribution system, and power control and management system all together. The move to IPS design will significantly improve efficiency, effectiveness, and survivability. To meet the needs of the US Navy, enhancing survivability by reducing susceptibility to damage, a IPS prefers decentralized reconfiguration system is preferred for IPS instead of traditional reconfiguration techniques used for terrestrial power grids. A multi-agent system (MAS) is a loosely coupled network composed of several agents. These agents interact with their environments and communicate with each other to solve problems that are beyond the individual capabilities or knowledge of each single agent. Because of its decentralized feature and lack of a global control feature, MAS appears to be the best candidate for IPS reconfiguration. This research work proposes a new model of an IPS, based on the Naval Combat Survivability, DC Distribution Test-bed (NCS DCDT). The new model combines the electric power generation system, electric propulsion system, and AC-DC zonal distribution system. To decrease the probability of distribution zones losing power, the new model modifies original design of the zonal distribution system in NCS DCDT. Another main endeavor of this research work is to design a MAS for reconfiguration of an IPS with AC-DC zonal distribution system. The MAS consists of three sub-MAS, named power generation MAS, propulsion MAS, and distribution MAS, and includes forty-one different agents which are instances of nineteen different abstract agent classes. The MAS is implemented with JAVA/JADE software and simulated on a platform of JADE 3.4.1 and JAVA jdk 1.5.0_08. Simulation results show that the MAS can execute reconfiguration functions such as fault area isolation, automatic switching, and load shedding.

Master of Science / Department of Electrical and Computer Engineering / Sanjoy Das / Noel Schulz / Electrical power, although convenient form of energy to distribute and use, cannot easily be stored in large quantities economically. Most electrical power generated by utility plants is consumed simultaneously in real time. However, in some cases, energy storage systems become crucial when power generated from sources does not fulfill peak power load demand in a power system or energy storage systems are needed as backup. Due to these reasons, various technologies such as batteries, ultracapacitors (UC), superconducting magnetic energy storage (SEMS) and flywheels are beneficial options for energy storage systems. Shipboard power systems must use one or more energy storage systems in order to backup the existing power system if locally generated power is unavailable. This will lessen the effect of voltage sags on power quality, and improve system reliability. This report mainly focuses on the design of a Boost DC-DC converter and the integration of that converter with a previously designed battery storage model, as well as the effect of varying loads at the end of the converter.

Medium-Voltage Direct-Current (MVDC) power system has been considered as the trending technology for future All-Electric Ships (AES) to produce, convert and distribute electrical power. With the wide employment of highrequency power electronics converters and motor drives in DC system, accurate and fast assessment of system dynamic behaviors , as well as the optimization of system transient performance have become serious concerns for system-level studies, high-level control designs and power management algorithm development. The proposed technique presents a coordinated and automated approach to determine the system adjustment strategy for naval power systems to improve the transient performance and prevent potential instability following a system contingency. In contrast with the conventional design schemes that heavily rely on the human operators and pre-specified rules/set points, we focus on the development of the capability to automatically and efficiently detect and react to system state changes following disturbances and or damages by incooperating different system components to formulate an overall system-level solution. To achieve this objective, we propose a generic model-based predictive management framework that can be applied to a variety of Shipboard Power System (SPS) applications to meet the stringent performance requirements under different operating conditions. The proposed technique is proven to effectively prevent the system from instability caused by known and unknown disturbances with little or none human intervention under a variety of operation conditions. The management framework proposed in this dissertation is designed based on the concept of Model Predictive Control (MPC) techniques. A numerical approximation of the actual system is used to predict future system behaviors based on the current states and the candidate control input sequences. Based on the predictions the optimal control solution is chosen and applied as the current control input. The effectiveness and efficiency of the proposed framework can be evaluated conveniently based on a series of performance criteria such as fitness, robustness and computational overhead. An automatic system modeling, analysis and synthesis software environment is also introduced in this dissertation to facilitate the rapid implementation of the proposed performance management framework according to various testing scenarios.

The Medium Voltage DC (MVDC) architecture of shipboard power system (SPS) with higher power density and enhanced power control is seen as a future prospect in warships by US Navy. Optimal operation of SPS is essential to enable efficient power and energy usage in the tightly coupled and power limited systems. It helps in obtaining adequate and reliable power supply by rescheduling generator output and energy storage devices for different operating scenarios and can also ensure power supply to critical loads during fault conditions. The self-commutated Voltage Source Converters (VSCs) with high dynamic performance and independent control over the real and reactive powers are best suited in the MVDC architecture. Therefore, an optimal operation tool is developed for the multi-terminal VSC based MVDC SPS which minimizes the system operating costs by optimally coordinating generators and energy storage, and will also implement preventive and corrective actions for managing credible contingencies.

With the improvements in computer technology, users in utilities expect to receive more advanced functions of their power system management applications by using the data distributed among computer applications. The conventional method of point-to-point interface is not efficient for building large-scale computer systems and is especially difficult for system integration. Integration efforts are carried on to facilitate software applications communicating with others. Defining the same description for a central database and exchangeable data format among applications is the first step for integration. Since current data models in the Common Information Model (CIM) are designed mostly for analyzing the terrestrial transmission power system, they are not sufficient for Shipboard Power Systems (SPS). In order to facilitate software integration in SPS, a fundamentally common semantic for SPS applications needs to be extended from the current CIM. Therefore, these analysis applications for SPS could communicate with each other based on a standard model. In this thesis, a pulsed load model is extended from CIM. This model is a general time dependent pulsed load and the simulation of pulsed railgun load validates the proposed data model. Also, stress upon the power grid caused by the pulsed load is analyzed and the continuous railgun operation is simulated. In addition, new CIM data models are built for passive and active filters to facilitate system simulation and further application. As an active filter is a device that incorporates complicated control strategies, much work focused on finding a general data model to accommodate most common active filters. Finally the simulation for active filter validates the proposed data model.

Real time monitoring of the shipboard power system is a complex task to address. Unlike the terrestrial power system, the shipboard power system is a comparatively smaller system but with more complexity in terms of its system operation. This requires the power system to be continuously monitored to detect any type of fluctuations or disturbances. Planning metering systems in the power system of a ship is a challenging task not only due to the dimensionality of the problem, but also due to the need for reducing redundancy while improving network observability and efficient data collection for a reliable state estimation process. This research is geared towards the use of a Genetic Algorithm for intelligent placement of meters in a shipboard system for real time power system monitoring taking into account different system topologies and critical parameters to be measured from the system. The algorithm predicts the type and location of meters for identification and collection of measurements from the system. The algorithm has been tested with several system topologies.

The protection system in a shipboard power system plays a vital role in detecting the fault conditions, isolating the faulted zone and preventing the fault propagation into other vital sections onboard the ship. The protection system should be able to remove faults and restore the service to all the vital loads rapidly. In order to design the protection system, preliminary hardware-in-the-loop testing is done using bus differential relay hardware and a Real Time Digital Simulator (RTDS). In this thesis work, based upon the functionalities of the relay hardware the software differential relay model is designed and simulated using the RSCAD Version 2.00 software suite and RTDS. The software differential relay model developed in RSCAD was tested on a terrestrial power system and a shipboard power system test case for various fault conditions, and its functionalities are validated based upon the hardware-in-the-loop test results.