abstract: This research mainly focuses on improving the utilization of photovoltaic (PV) re-sources in distribution systems by reducing their variability and uncertainty through the integration of distributed energy storage (DES) devices, like batteries, and smart PV in-verters. The adopted theoretical tools include statistical analysis and convex optimization. Operational issues have been widely reported in distribution systems as the penetration of PV resources has increased. Decision-making processes for determining the optimal allo-cation and scheduling of DES, and the optimal placement of smart PV inverters are con-sidered. The alternating current (AC) power flow constraints are used in these optimiza-tion models. The first two optimization problems are formulated as quadratically-constrained quadratic programming (QCQP) problems while the third problem is formu-lated as a mixed-integer QCQP (MIQCQP) problem. In order to obtain a globally opti-mum solution to these non-convex optimization problems, convex relaxation techniques are introduced. Considering that the costs of the DES are still very high, a procedure for DES sizing based on OpenDSS is proposed in this research to avoid over-sizing. Some existing convex relaxations, e.g. the second order cone programming (SOCP) relaxation and semidefinite programming (SDP) relaxation, which have been well studied for the optimal power flow (OPF) problem work unsatisfactorily for the DES and smart inverter optimization problems. Several convex constraints that can approximate the rank-1 constraint X = xxT are introduced to construct a tighter SDP relaxation which is referred to as the enhanced SDP (ESDP) relaxation using a non-iterative computing framework. Obtaining the convex hull of the AC power flow equations is beneficial for mitigating the non-convexity of the decision-making processes in power systems, since the AC power flow constraints exist in many of these problems. The quasi-convex hull of the quadratic equalities in the AC power bus injection model (BIM) and the exact convex hull of the quadratic equality in the AC power branch flow model (BFM) are proposed respectively in this thesis. Based on the convex hull of BFM, a novel convex relaxation of the DES optimizations is proposed. The proposed approaches are tested on a real world feeder in Arizona and several benchmark IEEE radial feeders. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016

Orientador: John Fredy Franco Baquero / Resumo: O planejamento bem-sucedido de redes de distribuição requer uma metodologia que inclua um modelo de rede preciso que considere não apenas os custos econômicos, mas também os custos associados à confiabilidade do sistema. Considerando estas duas características essenciais, esta tese propõe modelos matemáticos que permitam incluir a avaliação da confiabilidade dentro do problema do planejamento de expansão de sistemas de distribuição com múltiplos estágios, visando expandir os ativos de rede (ramos e subestações) e minimizar os custos de confiabilidade do sistema. Em relação às características da rede, o modelo de planejamento proposto utiliza um fluxo de potência AC não-linear e não convexo, que é convertido em um problema convexo usando reformulação cônica, técnicas de linearização por partes, com o intuito de obter tratabilidade computacional usando técnicas clássicas de otimização. Além disso, a avaliação de confiabilidade convencional baseada em simulação é implementada de forma equivalente por meio de expressões algébricas dentro do modelo matemático. Vários casos de estudo são usados ​​para demostrar a eficácia da metodologia de planejamento proposta. / Abstract: Successful planning of distribution networks requires a methodology that includes an accurate network model that considers not only the economic costs but also the costs associated with system reliability. Considering these two essential characteristics, this thesis proposes mathematical models that include reliability assessment within multi-stage expansion planning problem of distribution systems, aiming at expanding network assets (branches and substations) and minimizing reliability costs of the system. In relation to the network characteristics, the proposed planning model uses a non-convex nonlinear AC power flow, which is converted into a convex problem using conic reformulation and piece-wise linearization, to obtain the computational treatability using classical optimization techniques. In addition, conventional simulation-based reliability assessment is implemented equivalently through algebraic expressions. Several benchmarks are used to demonstrate the effectiveness of the proposed planning methodology. / Doutor

Orientador: Prof. Dr. Edmarcio Antonio Belati / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2017. / Os sistemas elétricos de Potência englobam os campos da engenharia elétrica que tratam da geração, transmissão e distribuição de energia elétrica. A confiabilidade e otimização são itens de suma importância para o funcionamento correto e eficiente das instalações elétricas. Esta pesquisa tem o seu foco voltado para os sistemas de distribuição, tratando especificamente da reconfiguração desses sistemas visando minimizaras perdas ativas. A reconfiguração é uma boa estratégia para diminuir perdas, pois demanda um baixo custo de investimento e apresenta resultados eficazes. Por tratar-se de um problema de otimização (minimização das perdas), o mesmo está sujeito às restrições impostas: 1) manutenção da radialidade; 2) ilhamento de cargas; 3) limite de tensão admissível nos nós; 4) balanço de potências do sistema. O método apresentado neste trabalho para a solução dessas questões baseia-se em uma metaheurística desenvolvida a partir da observação do comportamento e interação socioambiental de vaga-lumes. Através do seu tratamento e adequação ao problema, o algoritmo desenvolvido será utilizado em conjunto com um Fluxo de Carga CA para a determinação das perdas. Também é estabelecido um critério para diminuir o espaço de busca dos sistemas, tornando a busca pelo ponto ótimo mais eficaz. As simulações computacionais do método proposto foram realizadas em sistemas teóricos e reais e, os resultados, comparados com outros disponíveis na literatura especializada. / The Electrical Power Systems covers the electrical engineering fields that deal with electrical energy generation, transmission and distribution. Reliability and optimization are one of the most important subjects concerning the correct and efficient operation of electrical facilities. This research focuses on the distribution system, dealing specifically with its reconfiguration aiming active losses reduction. Reconfiguration is a good strategy for loss decreasing, because demands a low investment cost and shows efficient results. As an optimization problem (loss reduction), the same is subject to the imposed constraints: 1) radiality; 2) load islanding; 3) bus voltage limit; 4) system load flow balance. The method presented for this issues solution, is based on a metaheuristic developed through the observation of fireflies behavior and socioenvironmental interaction. Through its treatment and adjustment to the problem being studied, the algorithm developed will be applied with an AC Power Flow to determine active losses. Also, is proposed a criterion to reduce the systems search space, to improve the accuracy of the optimum point search. The computational simulations of the method herein proposed were performed on theoretical and real systems and, its results, compared with other methods applied by the authors of the specialized literature.