High precision control strategy for three-phase four-wire Shunt Active Power Filter

Three-phase four-wire Shunt Active Power Filters (SAPFs) can not only compensate the harmonics and reactive power for kinds of unbalanced nonlinear loads, but also suppress the neutral current. According to the disadvantages of conditional control strategies in dq0 frame for APF systems, a control strategy based on abc frame for three-phase four-wire SAPFs is presented. It achieves the control of DC-bus voltage and compensation currents in time domain and there is no coupling among each phase. What´s more, the selective harmonic detection method based on Discrete Fourier Transformation (DFT) algorithm and the compound current control strategy consists of Proportional-Integral (PI) controller and repetitive controller are adopted. Consequently, excellent compensation performances both in balanced and unbalanced load are achieved. Experimental results of a 16.5-kVA laboratory prototype prove its efficiency and feasibility.