An auxiliary unit with selective harmonic suppression and inherent reactive power compensation for civil distribution networks

Abstract

In view of the fact that there are usually two dominant harmonic currents and large amounts of inductive loads in residential distribution networks and low voltage distribution networks (called civil distribution networks in the paper), an auxiliary unit with selective harmonic suppression and inherent reactive power compensation for civil distribution networks is proposed in this paper. The proposed auxiliary unit consists of a passive part and an active inverter part. The passive part is composed of a compensation capacitor and two series resonance circuits tuned at the frequencies of the two dominant current harmonics. The passive part is used to compensate reactive power with a constant capacity and reduces capacity requirements of the active inverter part as well as voltage ratings of active inverter part. Owing to the low-impedance of the series resonance circuits, the vast majority of compensation currents generated by the active inverter part are injected to grid. These characteristics have been verified by experiment results. It is indicated that the proposed auxiliary unit is a preferred topology for improving power quality in civil distribution networks.