A Modified Repetitive-Based Controller for an Active Filter to Compensate Harmonics 6k+/-1

The paper presents a repetitive-based controller for a three-phase three-wire shunt active filter aimed to compensate reactive power and harmonic distortion in the case of distorted and unbalanced source voltages and load currents. The repetitive scheme used here is aimed to compensate specifically the harmonics 6k +/- 1 (k = 0, 1, 2,..., infinity) of the fundamental frequency. The scheme includes a damping gain to somehow limit the infinite gain produced, also a simple low pass filter (LPF) is included to restrict the bandwidth. However, this modifications cause inaccuracies in the frequency response, basically a considerable phase shift arises at the expected frequencies. In this work practical modifications are proposed for this scheme to minimize the negative effects caused by the introduction of the damping gains and the LPR Experimental results in a 2 KVA prototype and experiments of the algorithm itself are provided to illustrate the merits of our solution.