Output Impedance Control Method of Inverter-Based Distributed Generators for Autonomous Microgrid

The droop method is the most favorable alternative in microgrid implementations for autonomous control of grid-forming inverter-based distributed generators (DGs) connected in parallel. However, the dynamic characteristic of the conventional droop method is poor because the inertias of inverter-based DG units are extremely low and the transmission line is normally very short. An output impedance control method to enhance the dynamic performance and minimize the circulating current between grid-forming DGs is devised in this study. It is shown that it also enhances the power and harmonic sharing accuracy. The proposed method utilizes the virtual output impedance as a control signal for reactive power flow management. The effectiveness of the proposed scheme is validated using the high-speed field programmable gate array (FPGA)-based real-time hardware-in-the-loop test results.