Online Parameter Tuning Method of Multi-Resonant Controller for Grid-Forming Inverters

Grid-Forming inverters are expected to offer sinusoidal voltage in islanded ac microgrids, where harmonic current generated by nonlinear loads may cause distortion of the output voltage. The proportional multi-resonant controller is widely used for harmonic voltage compensation, but the resonant gains are usually fixed, which may result in poor output voltage waveform quality when the load characteristics change. To handle this issue, this paper proposes an online parameter tuning method of the multi-resonant controller. Based on the gradient descent algorithm, resonant gains are calculated online to optimize the allocation of resonant gains. The proposed method can ensure that better harmonic compensation performance is achieved and the system stability is guaranteed. Experimental results are presented to verify the effectiveness of the proposed method.