New structure of frequency self-adaptive selective harmonics repetitive control for the grid-connected converter

A new structure of selective harmonics repetitive control (NS-SHRC) scheme is first proposed. The proposed frequency self-adaptive NS-SHRC (FSA-NS-SHRC) is achieved by combining NS-SHRC with an infinite impulse response (IIR) filter. It is capable of effectively attenuating the impact of frequency fluctuation. NS-SHRC is a superior control scheme compared with conventional repetitive control and selective harmonic repetitive control in terms of dynamic response, frequency adaptability and steady-state tracking accuracy. This paper presents a comparison of the differences in computational burden and harmonic suppression ability between the IIR filter and finite impulse response (FIR) filter when applied to NS-SHRC. The proposed FSA-NS-SHRC is capable of solving the problem of resonance point mismatch caused by fundamental frequency fluctuation. Furthermore, the proposed control scheme can achieve precise and fast recognition of periodic reference signals with self-adaptive performance at various frequencies. The design method and digital control system of FSA-NS-SHRC are proposed. Experiments are conducted in a three-phase grid-connected control system. The results validate the effectiveness and advantages of FSA-NS-SHRC.