Current control strategy research for active power filter

Compensating effect of three-phase shunt active power filters (APF) is totally decided by the design of controller. But many non-ideal factors, such as limited bandwidth of output current loop, the time lag of signal sensing circuit and generation of reference current etc, will deteriorate the compensation effect. Proportion-integral (PI) controller cannot be used simply to control the output current without any steady error due to its limited current tracking capability. In order to improve the APF compensation performance, a new control method named as zero-steady-error control at the synchronous rotating coordinate system is proposed. Through adding numbers of harmonic compensation to major harmonic currents, appointed order harmonic with outer control loop can achieve non-offset regulation, meanwhile other harmonics without outer control loop remains the compensation of traditional PI controller. The feasibility of this output current controller architecture is verified completely by theoretic analysis and experimental results in detail.