A Decentralized PCC Voltage Secondary Control Method Based on Small-AC-Signal Injection for Parallel Inverters in Islanded Microgrids

To deal with the voltage deviation problem at the point of common coupling (PCC), a decentralized secondary control based on the injection of an extra small-AC-signal (SACS) into the output voltage of each inverter is proposed in this paper. Equal compensation value from the secondary control (SC) can be guaranteed and the voltage at the PCC can be restored to the nominal value without communication links. Moreover, the proposed method can also endure the inaccurate line impedance and the start-up delay of SC making it suitable for practical applications. The effectiveness of the proposed method is demonstrated by the simulation and experimental results.