Parameter Design of Second-Order Sliding Mode Controller for LC-coupling Hybrid Power Filter Based on Describing Function

LC-coupling hybrid active power filter (LC-HAPF) is one of the most cost-effective solution for power quality problem in distribution networks, in which its performance is mainly affected by the current controller. Among the state-of-the-art current controllers for the LC-HAPF, the second-order sliding mode controller (SOSMC) performs a superior dynamic and steady-state performance simultaneously. However, the existing SOSMC design method did not consider the upper bound of the control parameters, which may lead to saturation effect and control performance degradation. In this paper, a SOSMC design method based on describing function (DF) is proposed, which contributes the upper bound design constraint. The DF control block diagram for the LC-HAPF enables frequency domain analysis of SOSMC. Moreover, the analytical upper bounds of the SOSMC's control parameters are provided to avoid the saturation effect. Finally, the advantages of the proposed SOSMC design based on DF are verified by simulation results compared with the existing SOSMC design method under low DC-link voltage condition.