Stability-Guaranteed Harmonic Suppression Method for Inverters Under Weak Grid

The grid voltage weighted feedforward scheme based on multiple resonant components is an effective method to improve the quality of injected grid current under weak grid conditions. However, when the grid strength is too low, the weighting coefficients must be designed to be small in order to ensure system stability, which significantly reduces the harmonic suppression performance. This paper proposes a grid voltage weighted feedforward method based on series impedance compensation, where appropriate impedance is inserted into the inverter's equivalent impedance path to increase the inverter's impedance magnitude and phase. Based on this, the weighting coefficients of the resonant components are designed, achieving high harmonic suppression capability under weak grid conditions while ensuring system stability. Simulation results demonstrate the effectiveness of the proposed method.