Integration of active filter and energy storage system for power quality improvement in microgrids

In order to improve the power quality of renewable energy-based microgrids when unbalanced non-linear loads and generations occur, the integration of active filter functions into energy storage systems has been investigated. A four-leg voltage-source inverter supplied by a lithium iron phosphate battery has been considered. A control system, aimed to integrate the battery energy management with the compensation of higher current harmonic components, has been proposed. For managing battery systems both as a shunt active filter and energy storage system, when unbalanced and non linear load conditions in microgrids occur, an instantaneous power-based approach has been developed. The simulation results, referred to a three phase non-linear load which is characterised by the presence of a significant neutral currents, have been reported and discussed at the aim of showing the advantage of the proposed energy storage configuration.