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.

Power conversion system design issues are expanding their role in information technology equipment design philosophies. These issues include not only improving power conversion efficiency, but also increased concerns regarding the cost and complexity of the power conversion design techniques utilized to satisfy the host system's total performance requirements. In particular, in computer system (personal computers, workstations, and servers) designs, the power "supplies" are rapidly becoming a limiting factor in meeting overall design objectives. This dissertation addresses the issue of simplifying the architecture of distributed power systems incorporated into computing equipment. In the dissertation's first half, the subject of the design of the distributed power system's front-end converter is investigated from the perspective of simplifying the conversion process while simultaneously improving efficiency. This is initially accomplished by simplifying the second-stage DC/DC converter in the standard two-stage front-end design (PFC followed by DC/DC conversion) through the incorporation of secondary-side control. Unique modifications are then made to two basic topologies (the flyback and boost converter topologies) that enable the two-stage front-end design to be reduced to an isolated PFC conversion stage, resulting in a front-end design that features reduced complexity and higher efficiency. In the dissertation's second half, the overall DC distributed power system design concept is simplified through the elimination of power processing conversion steps - the result being the creation of a high-frequency (HF) AC distributed power system. Design techniques for generating, distributing, and processing HF AC power in this new system are developed and experimentally verified. Also, an experimental comparison between both DC and AC distributed power systems is performed, illustrating in a succinct fashion the merits and limitations of both approaches. / Ph. D.

The electric power grid is operated with exceptionally high levels of reliability, yet recent large-scale outages have highlighted areas for improvement in operation, control, and planning of power systems.  Synchrophasor technology may be able to address these concerns, and Phasor Measurement Units (PMUs) are actively being deployed across the Western Interconnection and North America.  Initiatives such as the Western Interconnection Synchrophasor Program (WISP) are making significant investments PMUs with the expectation that wide-area, synchronized, high-resolution measurements will improve operator situational awareness, enable advanced control strategies, and aid in planning the grid. This research is multifaceted in that it focuses on improved operator awareness and alarming as well as innovative remedial controls utilizing synchrophasors.  It integrates existing tools, controls, and infrastructure with new technology to propose applications and schemes that can be implemented for any utility.  This work presents solutions to problems relevant to the industry today, emphasizing utility design and implementation.  The Bonneville Power Administration (BPA) and Western Electricity Coordinating Council (WECC) transmission systems are used as the testing environment, and the work performed here is being explored for implementation at BPA.  However, this work is general in nature such that it can be implemented in myriad networks and control centers. A Phase Angle Alarming methodology is proposed for improving operator situational awareness.  The methodology is used for setting phase angle limits for a two-tiered angle alarming application.  PMUs are clustered using an adapted disturbance-based probabilistic rms-coherency analysis.  While the lower tier angle limits are determined using static security assessment between the PMU clusters, the higher tier limits are based on pre-contingency operating conditions that signify poorly damped post-contingency oscillation ringdown.  Data mining tools, specifically decision trees, are employed to determine critical indicators and their respective thresholds.  An application is presented as a prototype; however, the methodology may be implemented in online tools as well as offline studies. System response to disturbances is not only dependent on pre-contingency conditions but also highly dependent on post-contingency controls.  Pre-defined controls such as Special Protection Schemes (SPSs) or Remedial Action Schemes (RAS) have a substantial impact on the stability of the system.  However, existing RAS controls are generally event-driven, meaning they respond to predetermined events on the system.  This research expands an existing event-driven voltage stability RAS to a response-based scheme using synchrophasor measurements.  A rate-of-change algorithm is used to detect substantial events that may put the WECC system at risk of instability.  Pickup of this algorithm triggers a RAS that provides high-speed wide-area reactive support in the BPA area.  The controls have proved effective for varying system conditions and topologies, and maintain stability for low probability, high consequence contingencies generally dismissed in today's deterministic planning studies. With investments being made in synchrophasor technology, the path of innovation has been laid; it's a matter of where it goes.  The goal of this research is to present simple, yet highly effective solutions to problems.  Doing so, the momentum behind synchrophasors can continue to build upon itself as it matures industry-wide. / Ph. D.

The modern day power grid is a highly complex system; as such, maintaining stable operations of the grid relies on many factors. Additionally, the increased usage of renewable energy sources significantly complicates matters. Attempts to assess the current stability of the grid make use of several key parameters, however obtaining these parameters to make an assessment has its own challenges. Due to the limited number of measurements and the unavailability of information, it is often difficult to accurately know the current value of these parameters needed for stability assessment. This work attempts to estimate three of these parameters: the Inertia, Topology, and Voltage Phasors. Without these parameters, it is no longer possible to determine the current stability of the grid. Through the use of machine learning, empirical studies, and mathematical optimization it is possible to estimate these three parameters when previously this was not the case. These three methodologies perform estimations through measurement-based approaches. This allows for the obtaining of these parameters without required system knowledge, while improving results when systems information is known. / Ph. D. / Stable grid operations means that electricity is supplied to all customers at any given time regardless of changes in the system. As the power grid grows and develops, the number of ways in which a grid can lose stability also grows. As a result, the metrics that are used to determine if a grid is stable at any given time have grown increasingly complex and rely on significantly more amounts of information. This information required in order to obtain the metrics which determine grid stability often has key limitations in when and how it can be obtained. The work presented details several methods for obtaining this information in situations were it was previously not possible to do so. The methods are all measurement based, which means that no prior knowledge about the grid is required in order to compute the values.

Small-signal stability is of great concern for distributed power systems with a large number of regulated power converters. These converters are constant-power loads (CPLs) exhibit a negative incremental input resistance within the output voltage regulation bandwidth. In the case of dc systems, design requirements for impedances that guarantee stability have been previously developed and are used in the design and specification of these systems. In terms of three-phase ac systems, a mathematical framework based on the generalized Nyquist stability criterion (GNC), reference frame theory, and multivariable control is set forth for stability assessment. However, this approach relies on the actual measurement of these impedances, which up to now has severely hindered its applicability. Addressing this shortcoming, this research investigates the small-signal stability of three-phase ac systems using measured d-q frame impedances. Prior to this research, negative incremental resistance is only found in CPLs as a results of output voltage regulation. In this research, negative incremental resistance is discovered in grid-tied inverters as a consequence of grid synchronization and current injection, where the bandwidth of the phase-locked loop determines the frequency range of the negative incremental resistance behavior, and the power rating of inverter determines the magnitude of the resistance. Prior to this research, grid synchronization stability issue and sub-synchronous oscillations between grid-tied inverter and its nearby rectifier under weak grid condition are reported and analyzed using characteristic equation of the system. This research proposes a more design oriented analysis approach based on the negative incremental resistance concept of grid-tied inverters. Grid synchronization stability issues are well explained under the framework of GNC. Although stability and its margin of ac system can be addressed using source and load impedances in d-q frame, method to specify the shape of load impedances to assure system stability is not reported. This research finds out that under unity power factor condition, three-phase ac system is decoupled. It can be simplified to two dc systems. Load impedances can be then specified to guarantee system stability and less conservative design. / Ph. D.

No description available.

Syftet med examensarbetet är att digitalt tillämpa en stabilisering av pendlingar i den aktiva effekten hos en synkrongenerator för vattenkraft kopplad till ett distributionsnät. Implementeringen är tänkt att ske i en PLC som redan hanterar andra delar av magnetiseringen. Effektstabiliseringen görs genom att en motverkande styrsignal skickas till magnetiseringsutrustningen vilken i sin tur påverkar generatorns uteffekt. Denna motverkande styrsignal kan tas fram på olika sätt. Två modeller, av IEEE standardiserade, för effektstabilisering undersöks, PSS1A och PSS2B. En Simulink-modell över ett distributionsnät med generator byggs upp för att testa effektstabiliseringen. Diskretisering av den ena standarden utförs för att digital implementering ska kunna ske. Tester utförs även på denna modell för att kunna validera dess funktion i jämförelse med den kontinuerliga. Den tidsdiskreta modellen görs om till ett matematiskt uttryck tillämpbart i PLC:n. Jämförelse sker mellan simuleringarna och den tillämpade modellen genom mätningar. / The purpose of the degree project is to make a digital realization of a stabilizer for oscillations in the active power from a hydropower synchronous generator, connected to a power network. The implementation is supposed to be done in a PLC which already handles part of the excitation system. The power stabilization is achieved by sending a counteracting reference signal to the excitation system which controls the generator’s output power. This counteracting signal can be achieved in several ways. Two existing models, standardized by IEEE, for power system stabilizing will be examined, PSS1A and PSS2B. A Simulink-model of a distribution net with a generator is constructed to test the stabilizers. To perform a digital implementation a discrete transformation of one continuous model is done. This discrete model is also tested to verify the function in comparison to the continuous one. The discrete model is reorganized in a form possible to implement in the PLC. Comparison between the simulated and the implemented model is made by measurement.

Hurricanes are a threat to power and telecommunication infrastructure. This work summarizes a method for hurricane characterization using the proposed Localized Tropical Cyclone Intensity Index(LTCII) as a model for estimating damages to Electric power infrastructure. The model considers the effect of storm surge, maximum sustained wind speeds, the duration of time for which the system has been under tropical storm conditions and the area swept by hurricane over land. The measurements focus on major load centers in the system. The validation of the outage data is discussed. The model is evaluated for hurricanes from 2004, 2005 and 2008 hurricane seasons. The degree of influence of various hurricane parameters on the damages suffered by electric power systems are discussed using case studies. The maximum outages are observed to follow a logistic regression curve with respect to log(LTCII), with a correlation of 0.85. The observed restoration times fit a 6th degree polynomial with an R2 = 0.6. The effects of time under tropical storm winds were observed to have great significance in the damage profile observed with the model. / text

Wind power generation influences on the quality of the power grid. Because wind velocity is consistently changing this change causes unstable wind power generation. Since more wind power is expected to be used in the future, it is crucial to study the influence of the wind penetration level on normalized-damping ratio and damped-resonant frequency. In this thesis three types of calculated data were used to analyze the effect of wind penetration level on the Texas power grid: the percentage of wind power generation in Texas, generator-unit trip damping coefficient, and damped-resonant frequency. The percentage of wind energy was calculated from wind data provided by the Electric Reliability Council of Texas. The damping coefficient and damped-resonant frequency values are the indicators of power system stability and were calculated from synchronized phase data from the Texas power grid. The synchronized phase measurements were collected from the University of Texas at Austin and the wind farm near the Mc-Donald observatory. The data analyzed in this paper were from September 2009 to February 2010. The wind data were correlated to the grid-stability indicators which allowed us to interpret the status of the power grid according to the wind penetration level. When the wind penetration level increased over 11 %, five generator trip events occurred with damping coefficient values ten times higher than those of the regular unit trips. Moreover, during those events, damped-resonant frequency values rose nearly four times higher than the frequency values of other events. The results of this study may lead us to the conclusion that simply increasing the capacity of wind power generation will cause the power system to become unstable, and this will result in low quality of electricity. Therefore, further study is needed to determine the optimum amount of wind power generation without causing instability in the power grid. / text