A railway power quality conditioner based on chain circuit using impedance-matching balance transformers

In order to compensate reactive power and eliminate the negative-sequence and harmonic currents of electrified railway system, a new railway power compensator (RPQC) is proposed. The RPQC consists of three single-phase voltage source converters based on the chain circuit inverters. It connects the railway traction power system directly without isolation transformer. Power rating of the conditioner can be increased simply by adding chain links in series. The proposed topology is suitable for traction power system with impedance-matching balance transformer. Regarding the traction substation as a control object, the power quality of the traction substation with RPQC can be improved integrally. The RPQC always makes the traction substation become a nearly balanced three-phase power system in the public grid whether the loads of two feeders are balanced or not. According to simulation results, the proposed RPQC is feasible, and it can compensate reactive power, harmonic, and negative-sequence currents in two feeders together.