Controle em espaço de estados utilizando lqr de conversores para aplicação em microrrede

Abstract

Studies related to microgrids have grown considerably in recent years, becoming one of the most famous research topics in the field of electrical engineering, in Brazil and abroad. In this context, this work presents the modeling and control of an alternating current microgrid fed directly by a photovoltaic generation unit and an energy storage system, operating in the connected and isolated mode from the electrical grid. The Perturb and Observe algorithm is used to track the maximum power point of the fixed set of photovoltaic solar panels. The energy storage system is used due to the intermittency of photovoltaic generation and is used during all operation of the microgrid ensuring DC link voltage control. The topology of the converter, which interfaces between the direct current bus and the electrical grid, is a single stage, and its main feature is its multifunctionality: when connected to the electrical grid, acting in the grid supplying mode, operating as current source, controlling the current injected into the point of common coupling. However, in the grid forming mode, isolated from the electrical grid, the converter operates as a voltage source, controlling the amplitude and phase of the voltage at the common coupling point. The structure of the converter used is the same in both operating modes, changing only the control strategies. The transition from the operation and control mode is carried out with the help of the islanding detection technique based on the negative sequence current injection, with the opening of the switch, which connects to the electrical grid, performed when the level of negative sequence of the voltage after islanding exceeds the rated operating limit. The modeling of the proposed system is performed in state spaces and its control based on full state feedback, whose gains were found using the linear quadratic regulator. Simulation tests were carried out to validate the system, which proved the efficiency of the multifunctional converter and also the energy storage system. In addition, experimental results of the converter in the network forming mode have also shown satisfactory results.