Switching-loss reduction technique in active power filters without auxiliary circuits

To reduce the active power filter (APF) system switching loss, the usual method is to apply different soft-switching techniques. However, this would increase the system initial cost. In this study, a switching loss and switching noise reduction control strategy for APF under reactive power and current harmonics compensation is proposed, which can be applied to the existing APF systems in worldwide, thus causing economic benefits. The minimum dc-link operating voltage of APF is computed through both fundamental and harmonic frequencies analysis. Then an adaptive dc-link voltage controller for the APF is proposed, such that the compensating range of the APF is adaptively varied according to the variation of the loading. Thus, the switching loss and switching noise of the APF can be lowered. Moreover, the design criteria of the proportional and integral gains of the adaptive dc voltage controller are presented and discussed. Finally, simulation and experimental results of a 110 V, 5 kVA APF experimental prototype are given to prove the validity of the proposed control strategy for the APF in current quality compensation, and at the same time reducing switching loss and switching noise during operation.