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Fractional Repetitive Control based on IIR Filter for Grid-connected Inverters

Conventional repetitive control (CRC) can track period reference signals with zero error, thus, it is widely employed in grid-connected current tracking and harmonics current suppressing of inverter systems. However, when the grid frequency fluctuates, the tracking and suppressing performance of CRC will deteriorate. In this paper, a fractional repetitive control (FRC) with frequency adaptive based on infinite impulse response (IIR) filter is proposed. The resonant frequency of FRC will match the grid fundamental frequency and harmonics frequencies by adjusting the coefficients of IIR filter on-line, and then the system adaptability to the grid frequency fluctuation is achieved. Finally, the simulation results show that the proposed FRC scheme can effectively reduce the tracking error and suppress harmonics of grid-connected inverter systems.