Harmonic compensation and resonance damping for SAPF with selective closed-loop regulation of terminal voltage

Shunt active power filter (SAPF) is conventionally designed to compensate harmonic currents from non-linear load. However, due to parallel resonance between line impedance and capacitive load, the distortion of the voltage at point of common coupling (PCC) and grid current may not be mitigated completely by traditional manner of SAPF. This paper investigates harmonic compensation and resonance damping combined control for SAPF with selective closed-loop regulation of PCC voltage. Through developing equivalent circuit model, physical principle of SAPF with the proposed scheme is analysed as well as resonance frequency shifting phenomenon. To compensate specified harmonic currents, compensation reference is extracted flexibly by means of improved recursive discrete Fourier transform algorithm with phase-angle compensation. Meanwhile, selective virtual conductance with proportional–integral (PI) regulation of PCC voltage is proposed to damp parallel resonance. Then, a zero steady-state error controller composed of ordinary PI and advanced repetitive controller in parallel under synchronous rotation frame is adopted to improve current tracking performance of SAPF. Experimental results are provided to verify the effectiveness of the proposed method.