Unified Model and the Sliding Mode Control Method of Active Power Filter

Active power filters dynamically generate compensation currents based on load currents, reducing harmonic currents and reactive power in the power grid. The existing control methods for parallel active power filters have poor robustness, and the compensation effect is not ideal when the load current changes dramatically, especially during load switching. A control method of active power filter is proposed, which controls the compensation current and DC side voltage uniformly. Establishment of parallel active power filter <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\alpha \beta$</tex> Based on the tracking control model in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\alpha \beta$</tex> coordinate system, a sliding mode control method is proposed to minimize the tracking error. The reachability of the control method is proved, and the value range of sliding mode surface parameters is determined. The simulation results show that when the THD value of the grid current is 21.54 %, the THD of the compensated grid current decreases to 3.75 %. The DC side voltage can remain stable near the reference voltage. The unified model sliding mode control method is stable and effective.