The thesis introduces an approach for obtaining higher level decision support information using electromagnetic transient (EMT) simulation programs. In this approach, a suite of higher level driver programs (decision support tools) control the simulator to gain important information about the system being simulated. These tools conduct a sequence of simulation runs, in each of which the study parameters are carefully selected based on the observations of the earlier runs in the sequence. In this research two such tools have been developed in conjunction with the PSCAD/EMTDC electromagnetic transient simulation program. The first tool is an improved optimization algorithm, which is used for automatic optimization of the system parameters to achieve a desired performance. This algorithm improves the capabilities of the previously reported method of optimization-enabled electromagnetic transient simulation by using an enhanced gradient-based optimization algorithm with constraint handling techniques. In addition to allow handling of design problems with more than one objective the thesis proposes to augment the optimization tool with the technique of Pareto optimality. A sequence of optimization runs are conducted to obtain the Pareto frontier, which quantifies the tradeoffs between the design objectives. The frontier can be used by the designer for decision making process. The second tool developed in this research helps the designer to study the effects of uncertainties in a design. By using a similar multiple-run approach this sensitivity analysis tool provides surrogate models of the system, which are simple mathematical functions that represent different aspects of the system performance. These models allow the designer to analyze the effects of uncertainties on system performance without having to conduct any further time-consuming EMT simulations. In this research it has been also proposed to add probabilistic analysis capabilities to the developed sensitivity analysis tool. Since probabilistic analysis of a system using conventional techniques (e.g. Monte-Carlo simulations) normally requires a large number of EMT simulation runs, using surrogate models instead of the actual simulation runs yields significant savings in terms of shortened simulation time. A number of examples have been used throughout the thesis to demonstrate the application and usefulness of the proposed tools.

The thesis introduces an approach for obtaining higher level decision support information using electromagnetic transient (EMT) simulation programs. In this approach, a suite of higher level driver programs (decision support tools) control the simulator to gain important information about the system being simulated. These tools conduct a sequence of simulation runs, in each of which the study parameters are carefully selected based on the observations of the earlier runs in the sequence. In this research two such tools have been developed in conjunction with the PSCAD/EMTDC electromagnetic transient simulation program. The first tool is an improved optimization algorithm, which is used for automatic optimization of the system parameters to achieve a desired performance. This algorithm improves the capabilities of the previously reported method of optimization-enabled electromagnetic transient simulation by using an enhanced gradient-based optimization algorithm with constraint handling techniques. In addition to allow handling of design problems with more than one objective the thesis proposes to augment the optimization tool with the technique of Pareto optimality. A sequence of optimization runs are conducted to obtain the Pareto frontier, which quantifies the tradeoffs between the design objectives. The frontier can be used by the designer for decision making process. The second tool developed in this research helps the designer to study the effects of uncertainties in a design. By using a similar multiple-run approach this sensitivity analysis tool provides surrogate models of the system, which are simple mathematical functions that represent different aspects of the system performance. These models allow the designer to analyze the effects of uncertainties on system performance without having to conduct any further time-consuming EMT simulations. In this research it has been also proposed to add probabilistic analysis capabilities to the developed sensitivity analysis tool. Since probabilistic analysis of a system using conventional techniques (e.g. Monte-Carlo simulations) normally requires a large number of EMT simulation runs, using surrogate models instead of the actual simulation runs yields significant savings in terms of shortened simulation time. A number of examples have been used throughout the thesis to demonstrate the application and usefulness of the proposed tools.

Modern power systems operate much closer to their stability limits than before. With the introduction of highly sensitive industrial and residential loads, the loss of system stability becomes increasingly costly. Reinforcing the power grid by installing additional transmission lines, creating more complicated meshed networks and increasing the voltage level are among the effective, yet expensive solutions. An alternative approach is to improve the performance of the existing power system components by incorporating more intelligent control techniques. This can be achieved in two ways: introducing intelligent local controllers for the existing components in the power network in order to employ their utmost capabilities, and implementing global intelligent schemes for optimizing the performance of multiple local controllers based on an objective function associated with the overall performance of the power system. Both these aspects are investigated in this thesis. In the first section, artificial neural networks are adopted for designing an optimal nonlinear controller for a static compensator (STATCOM) connected to a multimachine power system. The neurocontroller implementation is based on the adaptive critic designs (ACD) technique and provides an optimal control policy over the infinite horizon time of the problem. The ACD based neurocontroller outperforms a conventional controller both in terms of improving the power system dynamic stability and reducing the control effort required. The second section investigates the further improvement of the power system behavior by introducing an ACD based neurocontroller for hierarchical control of a multimachine power system. The proposed wide area controller improves the power system dynamic stability by generating optimal control signals as auxiliary reference signals for the synchronous generators automatic voltage regulators and the STATCOM line voltage controller. This multilevel hierarchical control scheme forces the different controllers throughout the power system to optimally respond to any fault or disturbance by reducing a predefined cost function associated with the power system performance.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The growing global demand for electricity, increasing scarcity of the conventional energy sources and the need to reduce environmental impacts contributed to the pronounced development of new technologies based on clean and renewable energy sources. In this context, the wind power is the technology that has had a greater development in recent decades. This source has played an important role in the advancement of alternative sources in the world energy matrix, because the technology is already consolidated and is economically viable. Accompanying the technological development of the alternative sources, the induction generator has stood out among the generators with the technology best suited to generating electricity for isolated energy systems. With this motivation, this thesis proposes a new configuration for an isolated wind energy conversion system using variable speed turbines, in which the induction generator is electronically excited by means of a static compensator. Also, the generator is associated to a shunt active filter for compensation of non-linear and unbalanced loads, and with a battery bank for energy storage and DC bus stabilization. It is also discussed the main problems with the induction generator related to the magnetization characteristic and its dynamic model, and the proposed solutions to mitigate these problems. The results confirm the effectiveness of the proposed wind energy conversion system, showing its operational capability with variable load and variable turbine speed. Finally it is presented the main conclusions of this work and suggestions for future works in the same line of research. / O crescente aumento da demanda mundial de energia elétrica, a escassez cada vez maior das fontes convencionais de energia e a necessidade de redução dos impactos ambientais contribuíram para o acentuado desenvolvimento de novas tecnologias baseadas em fontes limpas e renováveis. Neste contexto, a energia eólica foi uma das tecnologias que mais se desenvolveu nas últimas décadas. Esta fonte tem desempenhado importante papel no avanço das fontes alternativas na matriz energética mundial, pois é uma tecnologia já consolidada e viável economicamente. Acompanhando o desenvolvimento tecnológico das fontes alternativas, o gerador de indução tem se destacado dentre as tecnologias de geradores mais adequadas para sistemas isolados de geração de energia elétrica. Com esta motivação, esta tese propõe uma nova configuração de conversão de energia eólica isolada, utilizando turbinas de velocidade variável, na qual o gerador de indução é excitado eletronicamente por meio de um compensador estático. Ainda mais, o gerador é associado a um filtro ativo shunt para a compensação de cargas não-lineares e desbalanceadas e a um banco de baterias para armazenamento de energia e estabilização do barramento cc, comum aos conversores. São discutidos os principais problemas relacionados ao gerador de indução para esta aplicação através da característica de magnetização e do seu modelo dinâmico, com as soluções propostas para mitigar estes problemas. Os resultados práticos e de simulação obtidos comprovam a efetividade da configuração de conversão de energia eólica proposta, mostrando a capacidade de operação do gerador com carga variável e velocidade variável da turbina. Por fim são apresentadas as principais conclusões e sugestões para trabalhos futuros na mesma linha de pesquisa.

Orientador: Prof. Dr. Claudionor Francisco do Nascimento / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2014. / Os sistemas de distribuição de energia elétrica, de um modo geral, são radiais. Estes sistemas podem possuir problemas de qualidade da energia elétrica em suas barras, tais como os desequilíbrios de tensão e de corrente. Ademais, as redes de distribuição podem conter uma grande quantidade de cargas monofásicas e trifásicas desequilibradas, indutivas e não lineares, o que pode resultar nos seguintes problemas: baixo fator de potência, desequilíbrio de tensão e distorção harmônica. Nesse sentido, devido à dinâmica destas cargas e a ocorrência de fenômenos, como afundamento de tensão por partidas de grandes motores e curtos-circuitos, há a necessidade de solução destas anormalidades, com respostas rápidas de estabilização. De maneira a atender a esta necessidade, os resultados das recentes pesquisas baseadas na eletrônica de potência têm proporcionado a utilização de equipamentos capazes de trabalhar em sistemas de potência de alta tensão. Esse avanço permite aplicações de dispositivos FACTS (Flexible Alternating Current Transmission Systems) nas operações de flexibilidade e mitigação de problemas comuns às redes de energia elétrica de transmissão e de distribuição, melhorando, assim, a qualidade da energia elétrica, o que aumenta a confiabilidade destes sistemas. Com este propósito, o presente trabalho tem como objetivo principal o estudo e a modelagem de um DSTATCOM (Distribution Static Compensator) em um sistema de distribuição de energia elétrica com variações de tensão, avaliando os possíveis benefícios proporcionados a este sistema. Os resultados de simulação foram obtidos com o auxílio do software MatLab/Simuling. / Distribution systems of electric power, in general, are radial. These systems have power quality problems in their power bars, such as the voltage variations. Moreover, the distribution networks contain a large amount of single-phase and three-phase unbalanced loads, inductive and non-linear, which may result in the following problems: low power factor, voltage unbalance, and harmonic distortion. Accordingly, due to the dynamic loads and the occurrence of these phenomena, such as voltage sag matches by large motors and short circuits, there is a need for solution of these abnormalities, with responsive stabilization. In order to meet this need, the results of recent research based on power electronics have provided the use of equipment to work on systems of high voltage power. This advancement allows applications FACTS devices (Flexible Alternating Current Transmission Systems) flexibility in operations and mitigation of problems common to the networks of electricity transmission and distribution, thus improving the quality of electric power, which increases the reliability of these systems. For this purpose, the present work has as main objective the study and modeling of a DSTATCOM (Distribution Static Compensator) in a system of electricity distribution, evaluating the possible benefits provided to the electric power system. The simulation results were obtained with the aid of software Matlab/Simuling. The effectiveness of the work has been proven since the DSTATCOM installed, the distribution network operated within established standards.

No description available.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The growing demand for energy in electric systems has resulted in major operational difficulties related to voltage level control. This has led specialists to deal more strictly with the control of reactive power and voltage, mainly in the case of radial electric systems supplying seasonal loads. Amongst a variety of commercial solutions to provide voltage regulation arise the static compensators. These represent an alternative of great potential to control the power flow and improve the voltage profile of electric systems. In this context, the SCRSC or Saturated Core Reactor Static Compensator - made up of a magnetic core with special characteristics and capacitors in series and in parallel - becomes an interesting alternative, when compared to other types of equipment. The main advantages related to this product are: robustness, low cost, lower maintenance requirements and good performance. Within this scenario, the purpose of the present dissertation is to carry on further investigation related to a more comprehensive model and computational studies of transient, dynamic and steady state performance of an overall electrical system. Using a given system several studies are performed so as to highlight the equipment energization phenomena as well as the device effectiveness at compensating for system operational condition changes that require the use of voltage regulators to accomplish the power utility standards. / A crescente demanda de energia nos sistemas elétricos tem resultado em dificuldades crescentes na sua operação. Isso tem levado os especialistas a tratar o controle da potência reativa e da tensão com mais rigor, principalmente em sistemas elétricos com características radiais conciliados com cargas sazonais. Para isso, dentre as várias possibilidades encontradas no mercado, os compensadores estáticos destacam-se como uma alternativa de grande potencial para a melhoria do perfil de tensão dos sistemas elétricos. Neste cenário aparece um equipamento denominado por Compensador Estático à base de Reator a Núcleo Saturado, constituído por uma unidade magnética especial e bancos de capacitores em paralelo e em série. As propriedades construtivas e operativas deste dispositivo oferecem uma possibilidade técnica robusta, de baixo custo, com menores requisitos de manutenção e ainda, com adequado desempenho operacional no que tange ao processo da regulação dinâmica da tensão. Dentro desta linha de trabalhos, esta dissertação, complementando pesquisas anteriores, avança no sentido de oferecer uma modelagem mais completa do dispositivo e sua respectiva implementação computacional. Utilizando tais recursos, são realizados estudos investigativos sobre o desempenho do compensador em pauta diante dos processos de energização e também quando da ocorrência de súbitas variações operativas do complexo elétrico que determinam a necessidade de dispositivos para a estabilização da tensão dentro dos patamares requeridos. / Mestre em Ciências