Sistema fotovoltaico conectado à rede trifásica com controle das potências ativa e reativa para mitigar o afundamento momentâneo de tensão

Abstract

Photovoltaic distributed generation has gained an important role in the world energy matrix as it is a renewable source of low environmental impact and has a great potential for energy generation and its use on a large scale. The photovoltaic solar generation considered as unconventional is characterized as an intermittent source, as it strongly depends on weather conditions (temperature and irradiance). When dealing with the subject in a more specific way, it is worth noting that the increasing insertion of photovoltaic solar energy in the Brazilian energy matrix can contribute to the improvement on the voltage levels of the electrical distribution network, adequately supplying the active and reactive powers. The main objective is to propose an active and reactive power injection control to mitigate voltage sags. The suggested control strategy works together with a modified version of an automatic voltage regulator (AVR), where it will act on the active and reactive powers injected by the inverter to reduce the effects of voltage sags. In this way, the control will avoid possible shutdowns and damage to equipment connected to the grid. The voltage improvement can be perceived by consumers connected to the power system. Modifications to the model and parameters of the AVR are carried out to speed up its performance, thus identifying short-duration voltage variations and, consequently, the control acts by changing the powers, by decreasing the injection of active power and increasing the reactive power based on inverter capacity during momentary voltage dip. A 75 kW three-phase grid-connected photovoltaic system equipped with the proposed control was inserted in part of a distribution grid in block 1106 South of the city of Palmas, Tocantins, and different short-circuits (fault) were analyzed. All computer simulations were performed in Matlab/Simulink®. In the analysis of the results, it was observed that the improvement in the voltage levels, both for the electrical network and for consumers, attests to the effectiveness of the proposed control, and also, when the fault is cleared, all values return to the pre-fault condition, so the inverter operates on active power only.