Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Nowadays, the distribution networks of electricity are the segment of the electrical power systems that has experienced more changes, due in particular to the presence of distributed generation and the technological advances in the areas of instrumentation, automation, measurement, information technology and comunication. This work aims to present the modelling, the control and the operation management of a group of small-scale energy resources connected to the low voltage, which coordinated form a microgrid. The microgrid energy resources are solar photovoltaic sources, wind energy based on double fed induction generator and hydrogen fuel cell, and a storage system with batteries. Two conceptions are developed: a single-phase microgrid and a three-phase microgrid, both operating in connected mode and isolated from the utility. Each energy resource is connected to a point of common coupling through power converters. For each converter was designed a set of control loops. The master-slave strategy was used to control the converters and to microgrid management. In master-slave configuration only the master converter is designed to be the voltage reference and others operate as a current source. For managing the steady state operation of microgrids different operating scenarios were considered, with variation of load and generation levels, as well as changes in tariff flags, for load supply with economy and sources operating at maximum efficiency. The proposed systems operate satisfactorily fulfill the requirements of utility for synchronization and disconnection. The injected currents are below the allowed distortion level. In stand-alone mode, the system voltage remains within the appropriate level of amplitude and frequency. / Atualmente, as redes de distribuiÃÃo de energia elÃtrica sÃo o segmento dos siste-mas elÃtricos de potÃncia que mais tem experimentado mudanÃas, devido, em es-pecial, à presenÃa da geraÃÃo distribuÃda e aos avanÃos tecnolÃgicos nas Ãreas de instrumentaÃÃo, automaÃÃo, mediÃÃo, tecnologia da informaÃÃo e comunicaÃÃo. Este trabalho tem por objetivo apresentar a modelagem, o controle e o gerenciamento da operaÃÃo de um conjunto de recursos energÃticos de pequeno porte, conectados à baixa tensÃo, que coordenados formam uma microrrede. Os recursos energÃticos da microrrede sÃo fontes solar fotovoltaica, eolielÃtrica com gerador de induÃÃo de dupla alimentaÃÃo e cÃlula combustÃvel a hidrogÃnio, e um sistema de armazenamento de energia a baterias. Duas concepÃÃes de microrredes sÃo desenvolvidas: microrrede monofÃsica e microrrede trifÃsica, ambas operando em modo conectado e isolado da rede elÃtrica principal. Cada recurso energÃtico à conectado a um ponto comum de conexÃo atravÃs de conversores de potÃncia. Para cada conversor foi projetado um conjunto de malhas de controle. A estratÃgia mestre-escravo foi usada para o controle dos conversores e gerenciamento da microrrede. Na configuraÃÃo mestre-escravo apenas o conversor mestre à designado para ser a referÃncia de tensÃo que os outros conversores necessitam para operarem como fonte de corrente. Para o gerenciamento da operaÃÃo das microrredes em regime permanente, foram considerados diferentes cenÃrios de operaÃÃo, com variaÃÃo de nÃveis de carga e de geraÃÃo, bem como variaÃÃo de bandeiras e postos tarifÃrios, visando atender a carga com economicidade e fontes operando em mÃxima eficiÃncia. Os sistemas propostos operam de forma satisfatÃria obedecendo aos requisitos da concessionÃria para a sincronizaÃÃo e desconexÃo. As harmÃnicas de corrente injetada estÃo abaixo do nÃvel de distorÃÃo permitido. No modo isolado, a tensÃo dos sistemas permanece dentro do nÃvel adequado de amplitude e frequÃncia.

A growing need for clean and sustainable energy is causing a significant shift in the electricity generation paradigm. In the electricity system of the future, integration of renewable energy sources with smart grid technologies can lead to potentially huge economical and environmental benefits ranging from lesser dependency on fossil fuels and improved efficiency to greater reliability and eventually reduced cost of electricity. In this context, microgrids serve as one of the main components of smart grids with high penetration of renewable resources and modern control strategies. This dissertation is concerned with developing optimal control strategies to manage an energy storage unit in a grid-connected microgrid under uncertainty of electricity demand and prices. Two methods are proposed based on the concept of rolling horizon control, where charge/discharge activities of the storage unit are determined by repeatedly solving an optimization problem over a moving control window. The predicted values of the microgrid net electricity demand and electricity prices over the control horizon are assumed uncertain. The first formulation of the control is based on the scenario-based stochastic conditional value at risk (CVaR) optimization, where the cost function includes electricity usage cost, battery operation costs, and grid signal smoothing objectives. Gaussian uncertainty is assumed in both net demand and electricity prices. The second formulation reduces the computations by taking a worst-case CVaR stochastic optimization approach. In this case, the uncertainty in demand is still stochastic but the problem constraints are made robust with respect to price changes in a given range. The optimization problems are initially formulated as mixed integer linear programs (MILP), which are non-convex. Later, reformulations of the optimization problems into convex linear programs are presented, which are easier and faster to solve. Simulation results under different operation scenarios are presented to demonstrate the effectiveness of the proposed methods. Finally, the energy management problem in network of grid-connected microgrids is investigated and a strategy is devised to allocate the resulting net savings/costs of operation of the microgrids to the individual microgrids. In the proposed approach, the energy management problem is formulated in a deterministic co-operative game theoretic framework for a group of connected microgrids as a single entity and the individual savings are distributed based on the Shapley value theory. Simulation results demonstrate that this co-operation leads to higher economical return for individual microgrids compared to the case where each of them is operating independently. Furthermore, this reduces the dependency of the microgrids on the utility grid by exchanging power locally. / Thesis / Master of Applied Science (MASc)