A Decentralized Current Sharing Strategy for Islanded Resistive Microgrids Based on Iterative Virtual Impedance Regulation

The output impedances of inverters can be reshaped to improve current sharing accuracy in islanded microgrids. In this paper, a decentralized current sharing strategy based on iterative virtual impedance regulation (IVIR) is proposed. The whole IVIR process is decomposed into several continuous iterations. During each iteration, three stages are involved. In the first stage, a virtual impedance increment is generated with the integral of the inverter uniform output currents. Then, an impedance compensation is introduced to restore the voltage magnitude in the second stage. In the third stage, the current sharing error is judged. Based on this iterative regulation, the impedance mismatches are eliminated with small virtual impedances, all the balanced, unbalanced and harmonic current components are distributed accurately, and good voltage quality maintains. The proposed control strategy requires neither communication nor grid impedance knowledge. Simulation and experimental results are presented to verify the effectiveness of the proposed strategy.