Fuzzy soft-startup controller of active power filter

Shunt active power filter (APF) has been proved to be a useful approach to eliminate harmonics and reactive current. With ancient control strategies, there will be voltage overshoot and current impulse when active power filter is plunged into the whole system. This limits the development and practicability of active power filter. In order to solve this problem, a fuzzy controller with self-adjustable factor is proposed in this paper to control DC-link voltage of active power filter. The distinctive advantage of this fuzzy controller is that its fuzzy control rules can be modified according to real system states automatically and simultaneously, which can improve the dynamic performance and robustness of the system. In order to absorb the merits of PI controller and fuzzy controller simultaneously, a combined controller is designed. The combined controller can not only realize the soft-startup of active power filter, but also eliminate the steady state error. Finally simulation results verify the validity and effectiveness of the combined controller.