Frequency Adaptive Repetitive Control of New Energy Grid-Connected Inverter Based on Improved IIR

This article proposes a frequency adaptive repetitive control (FARC) strategy based on an improved infinite impulse response (IIR) filter for new energy grid-connected inverters. By changing the parameters of the IIR filter in real time, the FARC based on the improved IIR filter can achieve frequency adaptation. Considering the narrow effective gain bandwidth of repetitive control (RC), the tracking accuracy of RC is more sensitive to frequency fluctuations. Aiming at this problem, a method of adaptive delay number is proposed, in the case of a fixed sampling period. The method can update the delay coefficient of the filter in real time by introducing a new ladder structure in the IIR filter based on the Thiran algorithm, making the proposed FARC capable of frequency adaptation. The introduced ladder structure is easy to design and can address the complex problem of Thiran filter digital circuit implementation effectively. To verify the feasibility of the scheme, the improved frequency adaptive repetitive controller is theoretically analyzed, and the effectiveness and accuracy of the proposed FARC are verified by simulation and experiments.