Secondary control for reactive power sharing and voltage amplitude restoration in droop-controlled islanded microgrids

This paper focuses on the islanded operation of microgrids. In this mode of operation, the microsources are required to cooperate autonomously to regulate the local grid voltage and frequency. Droop control is typically used to achieve this autonomous voltage and frequency regulation. However, droop control has real and reactive power sharing limitations between the microsource inverters when there are mismatches between the output filter components and power line impedances. In this paper, secondary control loops were implemented to achieve equal reactive power sharing between the inverters and to restore the voltage deviations caused by the droop control. Primary droop control loops where implemented in the inverters to supply the real and reactive power. Simulation results are presented showing the feasibility of the proposed algorithm in achieving reactive power sharing between the inverters connected to the microgrid while simultaneously restoring the voltage deviations due to the droop control.