An improved repetitive control scheme for active power filter with frequency-adaptive capability

Active power filter (APF) based on repetitive control can achieve a zero steady-state error in compensating the harmonic currents caused by nonlinear loads. The repetitive delay structure must be a known integer. However, conventional repetitive control cannot exactly compensate the harmonic currents while the reference signals have a variable fundamental frequency. In this paper, a novel repetitive control scheme with frequency adaptive capability at a fixed sampling rate is proposed. A simulation model is built in the laboratory. Various simulation results demonstrate the effectiveness of the proposed repetitive control scheme.