An improved centralized/decentralized accurate reactive power sharing method in AC microgrids

Abstract

In AC microgrids, Conventional P-f and Q-V droop curves are adopted to share active and reactive power between converter-based distributed generations (DGs). Active power is shared with no error through the P-f droop curve, due to the same frequency all over the microgrids. But the reactive power cannot be shared accurately through the Q-V droop curve because of different bus voltages in microgrids, due to the feeders impedance mismatch. Centralized control methods are the most accurate methods for reactive power sharing. However, in centralized methods, a communication link (CL) failure leads to the reactive power sharing error (RSE). In this paper, a novel centralized/decentralized (C/DC) control method is proposed to remove the error in the CL failure situation until the CLs are restored. In this strategy, a centralized control method based on the adaptive virtual impedance is used to accurately share the reactive power before the CL fault, and the new proposed C/DC control method is utilized to remove the reactive power sharing error (RSE) after the CL fault. Consequently, unlike most control methods in the literature, a permanent accurate reactive power sharing is guaranteed through the proposed control strategy. Simulation results show the effectiveness of the proposed method.