A Decomposed Harmonic Current Suppression Method for VSG-Based Microgrids Connected to Distorted Grids

For virtual synchronous generator (VSG) based microgrids, it is challenging to address the adverse effect of nonlinear loads and grid background harmonics with existing harmonic suppression methods. To address this issue, a decomposed grid harmonic current suppression (DHS) method with proper feedforward point of common coupling voltage and feedback VSG output current as well as nonlinear load current is proposed for VSG-based microgrids. The proposed DHS method can separately mitigate the grid harmonic current caused by nonlinear loads and grid background harmonics, obtaining a promising harmonic suppression effect without potential system instability problem. Compared with conventional harmonic control methods, the DHS method reduces the control sensitivity to system parameters including line impedance, grid impedance, and system shunt capacitance, improving the adaptivity of harmonic control in distorted grids. The proposed method's effectiveness and reliability are verified by theoretical analysis and comparative experiments.