An Improved Repetitive Control for Active Power Filters with Three-Level NPC Inverter

Due to the difficulty of handling nonlinear loads for traditional active power filter(APF) with two-level inverter in high voltage high power grid, this paper researches three-level active power filters. This paper presents an improved repetitive scheme to control the shape of output current waveform. The design process of each part in the repetitive controller is presented. Q(z) is designed as a notch zero phase shift filter which degrade the high order harmonic severely with close-to-unit gain at low and medium frequency band. The revised filter, the phase compensator and the repetitive gain is also given. The control method has fast dynamic convergence rate and little static misadjustment. The experiment results illustrate that the performance of the proposed approach is satisfactory.