A Two-Leg Converter and Control Strategy to Compensate the Three-Phase Imbalanced and Harmonic Currents

In order to reduce the number of switches in the three-phase current compensation converter, a compensation scheme of two single-phase half-bridge back-to-back converters is proposed in this paper. In the traditional control, the active current is imbalanced and the reactive power cannot be fully compensated because the angle difference between line voltage and phase current is not considered. In order to solve this problem, a two-phase cross-decoupling control strategy of active and reactive currents is proposed. Firstly, the relation between active and reactive reference compensation currents and load currents is deduced based on the phase angle difference. According to this relation, the active and reactive currents of the single-phase converter are controlled respectively. To suppress the influence of load harmonic current on grid currents, a specific order harmonic control method is proposed. The simulation results show that compared with the traditional control strategy, the proposed control strategy can reduce the imbalance of three-phase current from 25% to 0.5%, increase the PF from 0.962 to 0.999, and compensate the grid harmonic currents.