A Novel Harmonic Sharing Scheme in Islanded Microgrid

For the islanded microgrid which is connected with nonlinear loads, an effective harmonic sharing method should be designed to guarantee the system stable operation. In this paper, a novel method of virtual impedance and PCC voltage compensation are proposed to achieve the harmonic sharing and voltage quality improvement at the point of common coupling (PCC). The fundamental and each harmonic currents are extracted by the fourth order band-pass filter respectively. Then large virtual impedance is added to the voltage reference for harmonic power sharing. However, large virtual impedance will cause large voltage drop at PCC. To avoid such occurrence, a PI controller is used to compensate the voltage drop without additional hardware. Simulation and experimental results validate the correctness and feasibility of the proposed method.