Abstract—To improve the high frequency compensation performance, LCL-filter is used instead of L-filter in three-phase four-wire active power filter (APF). In this paper, the characteristic of LCL-filter is discussed. The three-loop control strategy with active damping using capacitor current feedback is introduced. Then the system stability is analyzed by bode and zero-pole diagram, especially considering the time delay of the control system. The results of simulation and experiment prove the effectiveness and stability of the proposed control strategy.

Index Terms—Active Power Filter (APF), active damping, delay, lcl-filter, stability.

Longfei Li and Xinjian Jiang are with the Department of Electrical Engineering, Tsinghua University, Beijing 100084, China (e-mail: lilf11@ mails.tsinghua.edu.cn, jiangxj@ mail.tsinghua.edu.cn).