A proportional integral multi-resonance control scheme based on FIR filter for odd harmonic suppression

Repetitive control has been employed to grid current control owing to the high steady-state accuracy and good harmonics suppression ability. However, in a distributed generation system, the grid frequency will change in a certain range, which will cause deterioration of system stability. Therefore, a proportional integral multi resonance (PIMR) control scheme based on FIR filter is proposed to restrain odd harmonic of grid-connected inverter. While the frequency is variable, FIR filter coefficients can be adjusted online that the resonant frequency of PIMR can approximate to real grid frequency. This scheme can reduce the influence of grid frequency fluctuations on the system and suppress the odd harmonics excellently. Finally, simulation verified the effectiveness of the proposed control strategy.