Optimized harmonic detecting and repetitive control scheme for shunt active power filter in synchronous reference frame

Two optimized control schemes of shunt active power filter (SAPF) in balanced three-phase three-wire system are proposed in this paper, including a fast fractional-order repetitive control (RC) strategy and a computation reduced harmonic detecting method. The improved RC is implemented in the synchronous reference frame (SRF) and based on the fractional-delayed-filter. Compared with the conventional RC (CRC), the proposed strategy can reduce the repetitive period from one fundamental cycle to one-sixth of the fundamental cycle, which results in the faster dynamic response. The fractional-delayed-filter, as the delay part of the proposed improved RC strategy, is used to achieve the high tracking accuracy of reference signals for control systems with different sampling rates. This paper also proposes a harmonic detecting method in the SRF based on the sliding Discrete Fourier transform (SDFT) with reduced computational burden, catering for selective harmonic elimination. Simulations and experiments show the validity of the proposed solutions.