Decentralized voltage restoration method for droop controlled parallel operation inverters in AC microgric

摘要

This paper presents a new communication-independent voltage restoration method for droop controlled voltage source inverters. Major issues of decentralized control are categorized into the regulator synchronization and the line-impedance unbalance. For these issues, the proposed method restores voltage deviation individually by eliminating the interference of regulation control. The proposed decentralized controller is comprised of synchronized restoration control and cross current suppression control. Detection algorithm consisting of the moving average filter synchronizes load variation detection. However, the restoration control causes difference at the output voltage of each inverter under line-impedance unbalance. This voltage difference causes large cross current at the time of load variation, and causes abnormal rises of the DC-link voltage. The proposed cross current suppression control detects the cross current from the DC-link voltage rise, and suppresses it by correcting the output voltage. The proposed method only uses local measurements, so it provides high reliability in addition to the simplicity and scalability of system configuration. Both simulation and experimental results are presented to verify the effectiveness of the proposed method.