A DC Side Sensorless Single-Phase Shunt Active Power Filter with a Second Order Sliding Mode Control and Unbalance Loads

In this paper, a second order sliding mode control (SOSMC) method based on the super twisting strategy is introduced for the current control of a shunt active power filter (APF). This method is capable of alleviating the chattering phenomenon by smoothing the control input while showing satisfactory robustness even under distorted grid conditions. Furthermore, the DC side capacitor voltage is determined by leveraging the relationship between the compensating current and the accumulated charge in the capacitor. The energy storage relationship is applied to find the capacitor voltage indirectly instead of direct measurement. Following that, a basic proportional-integral (PI) controller is implemented to regulate the DC side capacitor voltage and generate the grid current reference. The simulation results, validated through MATLAB/Simulink, indicate that the proposed method is effective in regulating the DC side capacitor voltage and generating a sinusoidal grid current in the absence of harmonic disturbances. Furthermore, the proposed method displays encouraging behavior when exposed to distorted grid voltages.