Performance enhancement of active power filter in the presence of low order harmonics and distorted voltage

Dynamic characteristics of active power filter (APF) are dependent on APF control strategy performance. Synchronous reference frame (d-q) and instantaneous power theory (p-q) methods are the useful control strategies of APF. According to p-q and d-q methods, transient and steady state performance of the APF in these control methods is depends on the DC component separation speed and accuracy. The quick and accurate separation of DC component causes lower transient and THD in APF performance. So, in this paper, a discrete wavelet based low-pass filter (DWLPF) is proposed to improve the DC component separation speed and accuracy. To this end, three different methods are studied for discrete wavelet transform implementation and are compared with each other in transient response time, accuracy and computational cost. Afterward, the traditional low-pass filter (TLPF) in the p-q method is replaced by the new DWLPF to improve the DC component separation speed and accuracy and as a result enhancement of the transient and steady state performance of the three-phase APF. On other hand with fundamental extraction of point of common coupling (PCC) voltage using second order general integrator (SOGI), harmonics could be compensated by APF in a distorted voltage condition. The effectiveness of proposed method is examined by simulation and experimental results, which validates superiority of the proposed method.