Study on fuzzy controller with a self-adjustable factor of active power filter

Active power filter has been proved to be a useful approach to eliminate current harmonics caused by nonlinear loads. This paper proposes a fuzzy controller with self-adjustable factor to control DC-link voltage of active power filter. The distinctive advantage of the fuzzy controller is that its fuzzy control rules can be modified according to the real system states automatically and instantaneously, which can conquer the nonlinearity and uncertainty of power system. In the fuzzy controller design, the non-uniform quantization method is used for easy fuzzification and defuzzification. In order to absorb the merits of PI controller and fuzzy controller simultaneously, a combined controller is then designed. The combined controller has excellent performance in both steady and transient states. Furthermore a soft synchronization method based on sliding Fourier analysis in adopted to calculate the phase information of current reference. The whole system is simple, the calculating method is convenient to be realized and the effect is significant. Simulation and experiment results verify the effectiveness of the combined controller. It can greatly restrain voltage overshoot, reduce current impulse when APF is plunged into, improve the transient stability and dynamic response of the system and compensate reactive current and harmonics well.