A composite compensation method of a grid-connected AC/DC converter to improve robustness under weak grid conditions

Characterized by grid impedance variation and background grid voltage harmonics, weak grid may give rise to injected grid current distortion and cause stability issues in a grid-connected AC/DC converter. To lessen the effect, a composite compensation method is proposed in this paper based on output impedance model, which can increase control bandwidth and improve system's robustness against grid impedance variation and background harmonics. Simulations and preliminary tests are both conducted to verify that the proposed method can retain a good current harmonic suppression and system stability when the grid impedance varies or grid voltage harmonics are injected.