Accurate Reactive Power Sharing and Harmonic Mitigation in Islanded Microgrids Using Adaptive Virtual Capacitance

This paper presents an adaptive virtual capacitance control method for distributed generation (DGs) in an islanded microgrid to mitigate the voltage harmonics at the point of common coupling (PCC). To achieve the control target, the proposed method emulates the inverter output capacitance at the dominant harmonic frequency to compensate for the mismatched voltage drop on the line impedance. In addition, the virtual capacitance at the fundamental frequency is regulated to improve the reactive power sharing performance of the inverter units. The proposed capacitance control method is developed based on simple integral controllers without prior knowledge of the feeder impedances and local nonlinear load currents. By continuously adjusting the inverter output capacitance, the microgrid power sharing performance and voltage quality are ensured despite any load changes. The effectiveness and superiority of the proposed strategy are theoretically analyzed and verified.