Nonuniform Power Factor Partial Compensation for Compensating Current Reduction Using Particle Swarm Optimization in Traction Power Supply System

Railway power conditioner (RPC) can provide comprehensive reactive power, unbalanced current, and harmonics compensation in the traction power supply system. Under full compensation (FC), RPC can increase the three-phase power factor (PF) to unity but leads to high current rating and operation loss. In previous studies, partial compensation (PC) for the reduction of RPC current rating was proposed. An analytical solution of PC coefficients was used, which limits design freedom since identical PF is required at three-phase. This uniform power factor partial compensation (UPFPC) limits RPC in achieving a further reduction in its current rating. This article proposes a nonuniform power factor partial compensation (NPFPC), which can further reduce RPC current rating within the acceptable PF region and under the voltage unbalance threshold. However, determining an analytical solution under NPFPC is complicated, considering three degrees of freedom. This is achieved in this article by defining the lower boundary of grid side PFs and optimizing by particle swarm optimization. It is found through investigations that NPFPC can effectively reduce the compensating current rating by 56% compared to FC mode and 53% compared to UPFPC. Simulation and experimental results verify the validity of the proposed NPFPC.