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This work presents an alternative approach to power system computations, Graph Trace Analysis (GTA), and applies GTA to the power flow problem. A novel power flow algorithm is presented, where GTA traces are used to implement a modified Gauss-Seidel algorithm coupled with a continuation method. GTA is derived from the Generic Programming Paradigm of computer science. It uses topology iterators to move through components in a model and perform calculations. Two advantages that GTA brings are the separation of system equations from component equations and the ability to distribute calculations across processors. The implementation of KVL and KCL in GTA is described. The GTA based power flow algorithm is shown to solve IEEE standard transmission models, IEEE standard distribution models, and integrated transmission and distribution models (hybrid models) constructed from modifying IEEE standard models. The GTA power flow is shown to solve a set of robustness testing circuits, and solutions are compared with other power flow algorithms. This comparison illustrates convergence characteristics of different power flow algorithms in the presence of voltage stability concerns. It is also demonstrated that the GTA power flow solves integrated transmission and distribution system models. Advantages that GTA power flow bring are the ability to solve realistic, complex circuit models that pose problems to many traditional algorithms; the ability to solve circuits that are operating far from nominal conditions; and the ability to solve transmission and distribution networks together in the same model. / PHD / Power system engineers rely on modeling and analysis of the electric grid to ensure reliable delivery of that electricity to consumers. The algorithms currently being used for this purpose are designed to simulate either the high voltage transmission networks, or the low voltage distribution networks. The rapid growth solar photovoltaics (PV) based distributed generation over the last few years, which is expected to continue in the near future, has demanded a change in this modeling and analysis approach. As the penetration levels of distributed generation increase, accurate analysis of such an electric grid cannot be performed if either the distribution or the transmission network topology is neglected in the models. Integrated transmission and distribution system modeling and simulation, where transmission and distribution networks are modeled as one single unit, has become an important research area in recent years. This work contributes to this research area by presenting an algorithm that can be used to solve (find operating point) of integrated transmission and distribution system models. An algorithm that can find a solution of challenging network topologies and operating under severe conditions is also presented. Finally, an application of the algorithm is discussed where the impact of solar PV-based distributed generation on voltage stability limits of the electric grid is studied by using an integrated transmission and distribution system model. The dissertation shows that by solving integrated transmission and distribution system models using this algorithm, insights about the impact of solar PV-based distributed generation on the stability limits of the electric grid can be obtained, which the transmission only or distribution only models cannot provide.

With environmental and policy pressure to move towards cleaner fuel sources, wind energy is a proven technology that can be successfully implemented at the utility-scale and provide clean energy to the grid. Wind energy consists of many distributed wind turbines that are paralleled and connected to inject power to one location on the transmission grid. There are real power losses and reactive power drops that must be taken into consideration for these projects for plant performance and compliance. The better the performance of each new and operating wind farm installed, the more efficiently the grid operates as well as the less greenhouse gases generated. This thesis will first review the creation of an Excel tool to perform a load flow study given inputs for a wind farm using Newton-Raphson algorithms. Next, the results of the load flow analysis will be compared to an actual operating wind farm located in Texas to review the accuracy of the scenarios. Finally, alternative design and operating states for the wind farm are proposed and cases are simulated to review the impact on wind farm energy generation and reactive power provided to the grid. Finally, preferred improvements for future design and operational considerations are provided along with future areas of research and development. / Master of Science / This thesis is focused on improvements for wind farm design and operation to help wind farms generate more clean power to the grid. The thesis involves the creation of an Excel tool which can be used to complete required grid studies for real and reactive power flows within the wind farm to the point of connection with the transmission system. This analysis helps inform the wind farm design and operation to be more effective and operate more efficiently. An operating wind farm in Texas is explained and depicted for an understanding of how utility-scale wind farms are set up. Additionally, a year of data from an operating wind farm is used to compare the Excel load flow tool to actual data and confirm it's accuracy. Alternate methods this plant could have been designed and operated are evaluated using the new tool and actual operating conditions from the plant for the year under analysis are performed to better understand and quantify possible improvements for wind farms. This thesis is less focused on the wind turbine generator (WTG) construction and operation of a single unit, but rather focused on the output from the WTG and the impact on an entire system containing many of these distributed generators and their operation to provide energy to the grid.

The purpose of this investigation is to identify appropriate location of capacitor banks and sources of reactive power by studying power system stability in the vicinity of system equilibrium states. The locations for reactive power sources are determined by identifying those modes of the system that participate most in the system behavior in general and in dictating the final state of the system after experiencing faults or disturbances. To identify the relevant modes of the system that participate most in the system dynamic, we shall make use of modal and participation analysis for different system conditions. We also apply modal and participation analysis to a system in order to identify the components of greatest impact that result in the most efficient system control. The ideas developed in this study are used to analyze and identify weak boundaries of the IEEE 39- Bus system that contribute to the system’s instability.

O presente trabalho tem como objetivo propor uma metodologia para avaliar o impacto das diversas técnicas de repotenciação no desempenho de linhas de transmissão em regime permanente, visto que na atual literatura não existe uma análise abrangente que possa ser aplicada em qualquer linha de transmissão carente de repotenciação. A metodologia busca fornecer subsídios para escolha da técnica mais vantajosa para repotenciar uma linha, utilizando de forma extensiva, os fatores de desempenho, e de forma sintetizada, os índices de mérito agregado, que, avaliados individualmente e/ou em conjunto, propiciam informações qualificadas para as conclusões técnicas. Destaca-se que a proposição dos fatores de desempenho e dos índices de mérito são as principais contribuições deste trabalho. Para complementar a metodologia, uma análise de curtos-circuitos foi proposta. Os resultados da utilização da metodologia foram positivos, possibilitando verificar os ganhos de potência na transmissão de energia. Vale destacar a eficiência dos índices de mérito agregado, que identificaram a melhor técnica de repotenciação de forma sintetizada, resguardando a qualidade e enquadramento dos resultados nas normas regulamentadoras. / This work aims at proposing a methodology to assessing the impact of power upgrade techniques on the steady-state performance of transmission lines, since there is not anything similar to this in the technical literature. The proposed methodology aims at providing technical information to subside the choice of the best power line upgrade technique, by the extensive application of the performance factors and of the aggregate merit indices. It must be pointed out that the proposition of the performance factors and of the aggregate merit indices are the main contributions of this work. Additionally, a short circuit analysis was also proposed to assess the power upgrade techniques. The results after the method application were satisfactory and allowed verifying the surplus of power related to each upgrade technique. The contribution of the aggregate merit indices was very important to identifying the most favorable upgrade technique in a simple way, so that all statutory technical limits were not violated.

Orientador: Dílson Amâncio Alves / Banca: Francisco Villarreal Alvarado / Banca: Eduardo Nobuhiro Asada / Resumo: Este trabalho apresenta um novo esquema de parametrização geométrico para o fluxo de carga continuado que possibilita o traçado completo das curvas P-V, e o cálculo do ponto de máximo carregamento de sistemas de potência, sem os problemas de mau-condicionamento. O objetivo é o de apresentar de uma forma clara e didática, os passos envolvidos no desenvolvimento de uma técnica de parametrização geométrica a partir da observação das trajetórias de solução do fluxo de carga. A técnica associa robustez com facilidade de compreensão. A singularidade da matriz Jacobiana é eliminada pela adição da equação de uma reta que passa por um ponto no plano formado nas variáveis magnitude da tensão nodal e o fator de carregamento, dois parâmetros físicos de fácil compreensão. O uso desta técnica amplia o grupo das variáveis de tensão que podem ser usadas como parâmetro de continuação. Os resultados obtidos com a nova metodologia para os sistemas testes do IEEE (14, 30, 57, 118 e 300 barras), mostram que as características do método convencional são melhoradas e a região de convergência ao redor da singularidade é ampliada. Vários testes são apresentados com intuito de prover um completo entendimento do método proposto e possibilitar comparação e a avaliação do desempenho do esquema de parametrização proposto. / Abstract: This work presents a new geometrical parameterization scheme to the continuation power flow that allows the complete tracing of P-V curves and the computation of the maximum loading point of a power system, without ill-conditioning problems. The objective is to present in a clear and didactic way, the steps involved in the development of a geometrical parameterization technique from the observation of the behavior of power flow solutions path. The technique associates robustness with simplicity and easy interpretation. The Jacobian matrix singularity is overcome by the addition of a line equation which passes through a point in the plane determined by variables bus voltage magnitude and the loading factor, two physical parameter of easy understanding. The use of this technique enlarges the group of voltage variables that can be used as continuation parameter. The results obtained with the new methodology for the IEEE systems (14, 30, 57, 118 and 300 buses), show that the characteristics of the conventional method are improved and the region of convergence around the singular solution is enlarged. Many tests are also presented in intention to provide the complete understanding of the proposed method and to allow the comparison and assessment of the performance of the proposed parameterization scheme. / Mestre

O presente trabalho tem como objetivo propor uma metodologia para avaliar o impacto das diversas técnicas de repotenciação no desempenho de linhas de transmissão em regime permanente, visto que na atual literatura não existe uma análise abrangente que possa ser aplicada em qualquer linha de transmissão carente de repotenciação. A metodologia busca fornecer subsídios para escolha da técnica mais vantajosa para repotenciar uma linha, utilizando de forma extensiva, os fatores de desempenho, e de forma sintetizada, os índices de mérito agregado, que, avaliados individualmente e/ou em conjunto, propiciam informações qualificadas para as conclusões técnicas. Destaca-se que a proposição dos fatores de desempenho e dos índices de mérito são as principais contribuições deste trabalho. Para complementar a metodologia, uma análise de curtos-circuitos foi proposta. Os resultados da utilização da metodologia foram positivos, possibilitando verificar os ganhos de potência na transmissão de energia. Vale destacar a eficiência dos índices de mérito agregado, que identificaram a melhor técnica de repotenciação de forma sintetizada, resguardando a qualidade e enquadramento dos resultados nas normas regulamentadoras. / This work aims at proposing a methodology to assessing the impact of power upgrade techniques on the steady-state performance of transmission lines, since there is not anything similar to this in the technical literature. The proposed methodology aims at providing technical information to subside the choice of the best power line upgrade technique, by the extensive application of the performance factors and of the aggregate merit indices. It must be pointed out that the proposition of the performance factors and of the aggregate merit indices are the main contributions of this work. Additionally, a short circuit analysis was also proposed to assess the power upgrade techniques. The results after the method application were satisfactory and allowed verifying the surplus of power related to each upgrade technique. The contribution of the aggregate merit indices was very important to identifying the most favorable upgrade technique in a simple way, so that all statutory technical limits were not violated.

<p>The purpose of this thesis was to investigate the possibility of power flow control, on a section of a railway grid fed by rotary converters, using an extra feeding line. Two possible solutions for the power flow control were examined. The first using a series reactance in connection to each converter station and the second by changing the tap changer level of the transformer between the converter station and the feeding line.</p><p>In the two models a distance, comparable to the distance between Boden and Häggvik, in Stockholm, was used. The simulations were performed using the software SIMPOW.</p><p>The results from the performed simulations show that series reactances, under the stated conditions, can essentially improve the power flow. To implement this air coils with inductances in the approximate size of 10 to 45 mH could be used. Further, the tap changer levels of the transformer may be used, for individual converter stations, as a way to control the reactive power flow.</p>

The purpose of this thesis was to investigate the possibility of power flow control, on a section of a railway grid fed by rotary converters, using an extra feeding line. Two possible solutions for the power flow control were examined. The first using a series reactance in connection to each converter station and the second by changing the tap changer level of the transformer between the converter station and the feeding line. In the two models a distance, comparable to the distance between Boden and Häggvik, in Stockholm, was used. The simulations were performed using the software SIMPOW. The results from the performed simulations show that series reactances, under the stated conditions, can essentially improve the power flow. To implement this air coils with inductances in the approximate size of 10 to 45 mH could be used. Further, the tap changer levels of the transformer may be used, for individual converter stations, as a way to control the reactive power flow.