Negative‐Sequence Component Compensation for Railway Power System With Supercapacitor Integrated MMC

ABSTRACT This paper presents a coordinated control strategy for a supercapacitor‐integrated modular multilevel converter (SC‐MMC) to address the negative sequence component in railway traction power systems. The MMC is a single‐phase, four‐bridge‐arm topology with a traction‐side sub‐module connected to a supercapacitor energy storage device. The operating mode is divided based on the negative sequence compensation principle and locomotive load characteristics. The upper level of the strategy determines the operating modes and calculates the reference power of each port, while the lower level achieves power control and coordinates the switching of operating modes. The case study demonstrates that the system can effectively compensate for the negative sequence of the grid under different locomotive load levels and coordinate the control of the supercapacitor and MMC to participate in the compensation.