An Enhanced Droop Control Scheme for Islanded Microgrids

Due to the line impedance impact on islanded low-voltage microgrids, traditional droop control cannot guarantee the proper power sharing between distributed generation (DG) units. In the meanwhile, droop control would cause voltage and frequency deviation, which will influence the power quality of customers. This paper proposed an enhanced droop control scheme with autonomous frequency restoration control. Reactive power sharing problem is solved by adding a redesigned virtual impedance and voltage compensation loop, which ensures PCC voltage in nominal range. To the problem of frequency deviation, autonomous frequency restoration loop is added. Small signal model of frequency control is established to analyze the stability. In circumstance of frequent load switching, the frequency can properly restore to nominal value, with smooth and stable transient process. The simulation results demonstrate the effectiveness of the proposed control strategy.