Cophase Traction Power Supply System Based on Improved MMC-STATCOM-Vv Wiring

Abstract

A static synchronous compensator topology with an improved MMC (MMC-STATCOM) is proposed in this study after analyzing the modular converter (MMC) topology. The improved MMC uses fewer low-voltage power switching elements and is more economical compared to the traditional MMC. In the traction power supply environment without balancing equipment, the DC-side voltage balancing control of the converter is studied in depth, and a three-level control strategy is established. The first level of control is total voltage control, which achieves energy exchange between the converter and the power system through active power to achieve DC-side voltage balance. The second level of control is phase-to-phase voltage balancing control, which achieves phase-to-phase power redistribution by injecting zero-sequence voltage into the new topology converter. The third level of control is the intra-phase voltage balancing control, which ensures that the intra-phase module DC-side voltage is equal to the given value by controlling the DC voltage of each phase sub-module. In the same phase power supply environment, the compensation capability of the improved converter is analyzed to derive the compensation relationships for each port, and the compensation targets are achieved. Finally, the correctness of the control strategy and the compensation capability of the improved converter structure are verified by simulation experiments.INDEX TERMS DC-side voltage control, modular multilevel converter, static synchronous compensator, traction power supply