A hybrid railway power conditioner for traction power supply system

Co-phase traction power supply system was proposed for supplying the long-distance electrified railway without neutral sections. However, a railway power compensator (RPC) needs to be installed in each substation together with the traction transformer for improving the power quality. The RPC is mainly constructed by a back-to-back converter, which can reduce the unbalance currents by active power transfer and compensate reactive current and harmonics at the same time. A hybrid railway power conditioner (HRPC) is proposed for the co-phase traction power supply system in this paper. The HRPC uses a LC coupling branch between the converter and the traction supply. It is able to operate at a lower converter rating for achieving the same performance compared with conventional RPC. As a result, the initial cost and operational losses are reduced. The design of the LC coupling impedance and the DC bus voltage of the HRPC is focused on in this paper based on the mathematical models. The control system is implemented. Simulation results are provided and comparison with RPC is also given. Experimental results are provided to show the validity of the HRPC.