A decentralized negative sequence compensation method for islanded mirogrids

Single phase loads, which constitute the majority of low voltage consumers, give rise to unbalanced load currents in microgrids. As a consequence the voltage unbalance might rise beyond the permissible range. The voltage unbalance can be reduced by injecting a negative sequence (NS) compensation signal into the DERs reference voltage. However, such compensation might cause circulating currents between the DERs and also excessive current in the heavily loaded phases of some DERs. In this paper, a novel NS compensation method is proposed to reduce the circulating currents and eliminate the excess current in inverter-based microgrids. In this method, the NS voltages of the DERs are adjusted according to again scheduled NS droop method. The compensating signal is then computed by solving an optimization problem, which aims at tracking the NS voltage with minimum compensating action. Simulation results are proposed to verify the efficacy of the method.