A novel control strategy for active filters usable in harmonic polluted and/or imbalanced utility voltage case of 3-phase 4-wire distribution systems

This paper presents a new control strategy for parallel active filters. The instantaneous positive sequence extraction of load current and utility voltage is combined with the p-q theory. This method is able to control a four leg active filter for compensation of reactive power, current harmonics, three-phase imbalance and neutral current cancellation simultaneously in 3-phase 4-wire distribution systems. The presented method can operate in harmonic polluted and/or imbalance utility voltage case. The simulation results prove the considerable ability of control strategy to suppress the above-mentioned subjects with a very fast dynamic response. This method is also usable in 3-wire systems