Hybrid Railway Power Conditioner With Partial Compensation for Converter Rating Reduction

Single-phase traction transformers are widely used in traction power supply systems due to their characteristics such as a low cost and a simple structure. Railway power conditioners (RPCs) could increase the loading capacity of substations and improve the supply quality. In this paper, a hybrid RPC (HRPC) is applied to reduce reactive power, relieve system unbalance, and suppress harmonics. The operational voltage of the HRPC is much lower than that of a conventional RPC. A method named partial compensation was used to reduce the current rating of the RPC, in which the compensating currents are expressed as a function of the power factor target at the grid side. When this method is used in the HPRC, the operational voltage varies with the compensating currents over a wide range. A comprehensive design procedure is proposed so that both the current and voltage ratings of the HRPC are reduced with partial compensation. A reduction of more than 50% is achieved by compensating the power factor at the grid side to 0.95 instead of to unity. The control block diagram for the HRPC with partial compensation is presented. The design and control of the HRPC are validated by simulation and experimental results.