Research on Coordinated Control Strategy of Negative Sequence Current Compensation for Traction Power Supply System Under Unbalanced AC Grid

The Railway Power Conditioner (RPC) is designed to fully compensate for negative sequence current in the AC grid when the three AC grid voltages are symmetrically equal, but it is difficult to compensate for negative sequence currents in the AC grid when there is a voltage dip or phase jump in the AC grid voltage. To solve this problem, a coordinated control strategy for the compensation of negative sequence currents in traction power supply systems based on Dynamic Voltage Restorer (DVR) is proposed, whereby a railway power conditioner and a dynamic voltage restorer installed on the AC grid side work together to solve the negative sequence current problem. This paper first analyzes the effect of the negative sequence component of the AC grid voltage on the voltage and current of the traction power supply system, and then introduces the compensation principle of the coordinated control strategy. Finally, the efficiency of the control strategy proposed in this paper is verified by simulation and experiment.