A Frequency Adaptive PIMR-Type Repetitive Control for a Grid-Tied Inverter

A proportional integral multiresonant-type repetitive control (PIMR-type RC) has not only a better harmonic suppressing performance but also a faster error convergence rate. However, the harmonics suppressing performance of PIMR-type RC will significantly decrease when the grid fundamental frequency fluctuates in a large range. In this paper, an improved frequency adaptive PIMR-type RC (FA-PIMR-type RC) is proposed to cope with the frequency fluctuation in a large range. The improved PIMR-type RC is based on a fractional delay filter, which can be approximately realized by a finite impulse response filter. The varying fractional delay filters ensure that the resonant frequencies can match the actual reference frequency and harmonic frequencies. The synthesis, stability analysis, and parameters design criteria of the proposed FA-PIMR-type RC are given in this paper. The simulation and experimental results show that the improved PIMR-type RC can track grid reference signal, suppress harmonic signals, and have good error convergence rate under grid frequency fluctuation.