A novel active power filter based on high-accuracy harmonic current detection and sliding mode controller

A real-time digitalization method with high-accuracy and quick detection on harmonic and reactive currents in active power filter (APF) is proposed. Based on the principle of trigonometric function orthogonality and adaptive filter, a phase-lock control loop is constructed, the unit sine function in-phase with the fundamental wave of voltage and load current can be obtained, the amplitude of the fundamental wave can be obtained based on the sliding-window Fourier analysis, and then the reactive or harmonics current can be easily checked out accurately. Based on the time-domain analysis of three-phase three-wire active power filter current control loop, the common sliding-mode control strategy of current control loop is deduced. A new sliding-mode control strategy with variable reaching law is proposed, the current tracking error can be reduced quickly and chattering can be reduced effectively under the proposed sliding-mode control strategy. The proposed control strategy can provide both robustness response and a good dynamic response of the current tracking control, and has the characteristics of simple computation and easy application. The simulation and experiment results show its validity and feasibility.