Study on Repetitive Control of Current Loop in Active Power Filter

Three-phase shunt active power filter (APF) is often used to compensate the harmonic and reactive current derived from non-linear load. But many non-ideal factors, such as the limited bandwidth of output current loop and the time lag of signal sensing circuit and reference current generation 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. A novel output current control architecture in the synchronous rotating frame with ordinary PI and advanced repetitive controller (RC) in parallel is put forward in this paper to enhance the compensation characteristic of three-phase shunt APF. The advanced repetitive controller in parallel is used to eliminate the steady current tracking error caused by cyclic disturbance signal to improve the compensation precision of APF, while the ordinary PI controller is used to ensure the dynamic response performance of APF. The feasibility of this output current controller architecture is verified completely by theoretic analysis and experimental results in detail.