A waveform control technique for high power Shunt Active Power Filter based on repetitive control algorithm

Shunt Active Power Filters (SAPF) could restrain harmonic current in distribution grid effectively and their compensation precision relies heavily on the design of current loop controllers. Since the reference and feedback signal of the current controller are composed by different harmonic components and the bandwidth of conventional ProportionIntegral (PI) controller is limited, this controller cannot control the output current waveform without any steady error. In this paper, the limitation of conventional PI controller in the application of high power SAPF is analyzed firstly. Then the paper puts forward a double-loop composite controller composed by a PI inner loop and repetitive controller external loop to improve the output current waveform with the control object of LCL filters and the design method is given in detail. The controller could not only acquire high compensation precision when used to suppress odd harmonic, even harmonic current as well as negative sequence parts created by unbalanced load, but also guarantee excellent dynamic response performance. Finally, simulation and experimental results verify the composite controller gains extraordinary effects in high power SAPF.