Abstract
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.
Highlights
Traditional control schemes applied to shunt active power filters (SAPF), such as PI control, repetitive control (RC), proportional resonance control (PR), and their hybrid control, can compensate the current harmonics accurately in the stable power grid [1,2,3]
In the steady-state experiment, the harmonic steady-state compensation performance is verified by using sliding mode control (SMC), multiresonance sliding mode controller (MRSMC) and RCSMC
This paper proposes a novel sliding mode control scheme with a repetitive sliding surface for SAPF with an LCLCL filter, which effectively eliminates grid-connected harmonic current tracking errors and enhances the system robustness
Summary
Traditional control schemes applied to shunt active power filters (SAPF), such as PI control, repetitive control (RC), proportional resonance control (PR), and their hybrid control, can compensate the current harmonics accurately in the stable power grid [1,2,3]. For SAPF, the above methods have a limited tracking ability for harmonics, and ISMC is prone to problems such as large overshoot and long adjustment time, which deteriorate transient performance To address these deficiencies, [17] introduced a multi-resonance term of grid-connected current error on the sliding mode surface, and a multiresonance sliding mode controller (MRSMC) is proposed, which eliminated the grid-connected current tracking error by using the high-loop gain characteristics of resonance control to the periodic signal. Considering the advantages of RC with gain amplification for harmonics and non-static error tracking for periodic signals, 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.
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