Virtual Impedance Control Scheme to Compensate for Voltage Harmonics With Accurate Harmonic Power Sharing in Islanded Microgrids

In case of voltage harmonic compensation at the point of common coupling (PCC) in islanded microgrids, it is important to share the harmonic load power correctly among the distributed generators (DGs) to use the DGs' capacity effectively. In previous DG control schemes, it is impossible to satisfy the requirements of PCC voltage quality and accurate harmonic power sharing simultaneously with only a virtual impedance controller (VIC). In this article, we propose an enhanced DG VIC to provide accurate harmonic power sharing along with voltage harmonic compensation in islanded microgrids. The proposed VIC is developed based on simple integral controllers with two controllable parts and no information about the feeder impedances or load currents. The control performance is theoretically analyzed using a small-signal state-space model to evaluate the system dynamics and stability. The feasibility and effectiveness of the method are validated by simulated and experimental results.