This paper proposes a novel sliding mode control (SMC) scheme with a repetitive sliding surface for shunt active power filters (SAPF) to enhance the system robustness and eliminate harmonic current tracking errors. Traditional control schemes, such as PI control, repetitive control (RC), proportional resonance control (PR), improve the stability of the SAPF in the stable grid to a certain extent. However, the robustness of the SAPF control system has not been improved. In this paper, the SMC is applied to SAPF, and a sliding mode controller is constructed by using a linear sliding mode surface composed of the system state variables and a fast exponential power-reaching law, which can effectively enhance the system robustness. When the grid parameters change or external disturbances exist, sliding surface drift and sliding mode chattering will occur. Although fast-tracking of the harmonic current can still be achieved, it is difficult to accurately compensate AC harmonic current. Moreover, this may cause the harmonic current compensation error to be amplified. RC can achieve infinite gain at multiples of the fundamental frequency and can track inputs without static errors. In order to fully eliminate the harmonic current tracking error and effectively suppress the total harmonic distortion (THD) of the grid, the sliding mode surface was modified. An RC term of harmonic current error is introduced to the sliding mode surface, and a novel plugin-repetitive sliding mode control strategy (RCSMC) for SAPF is proposed. Finally, simulation and experiment results on the LCLCL-filter based SAPF show the effectiveness of the proposed control strategy.
A Modified Sliding Mode Control for Circulating Current Control and Voltage Balancing in Modular Multilevel Converter
