Digital Generalized Integrators of current control for three-phase Active Power filter with selective harmonic compensation

To improve the compensation performance of threephase Shunt Active Power filter (APF), a novel current control strategy was proposed based on Generalized Integrators (GI). The method employs an array of generalized integrators, one for the fundamental and the others for each harmonic, implemented in stationary frame. Due to the GI´s characteristics of the infinite open-loop gain and high selectivity, zero steady-state error and selective compensation strategy for the APF are achieved. The proposed controller is designed directly in Z-domain in order to eliminate the unexpected loss of gain and detuning of GI during digitalization processing. And a special digital phase-locked loop with fixed sampling points per line cycle is utilized to guarantee the frequency adaption of the GI in case of grid frequency varies. The superiority of the proposed control scheme is verified completely by both simulation and experimental results.