Dynamic Control and Analysis of DC-Capacitor Voltage Fluctuations in Three-Phase Active Power Filters

This paper proposes a new control method of three-phase active power filters for reducing the dc capacitor voltage fluctuations in transient load change. The proposed control method introduces a new k-step compensator, which maintains the mean active power flowing into the dc capacitor at zero every 1/(k-1) ac line period. Therefore, the compensator can suppress the transient voltage fluctuations across the dc capacitor even when a quick load change occurs. This paper theoretically reveals the relationship between the step number k and the reduction effect of the dc voltage fluctuations. The experimental setup introducing the proposed seven-step compensator exhibits a good suppression effect of the dc voltage fluctuations and makes it possible to reduce the required capacitance value of the dc capacitor by a factor of seven.