Modeling and Analysis of a Hybrid Co-Phase Traction Power Supply System Considering Minimum Compensation Capacity and Flexible Standby Strategy

The co-phase traction power supply system (TPSS) is an ideal solution for safe and efficient rail transit. To ensure reliability, the current topology adopts a 100% redundancy design, which results in high investment costs. To improve converter utilization and reduce costs, this paper proposes a hybrid co-phase TPSS (HCTPSS) and a coordinated control strategy between the primary power supply equipment (PPSE) and standby power supply equipment (SPSE) under N-1 equipment faults (single-converter failure). A comprehensive compensation model is derived to determine the minimum compensation capacity required for power quality improvement under both healthy and fault conditions, and a control strategy is developed to ensure reliable operation. Compared with existing combined co-phase TPSS, the HCTPSS can utilize existing Vv transformers, and compared with existing hybrid power quality conditioner schemes, it requires smaller converter installation capacity. Case studies and experimental results show that, for a practical traction substation retrofit, the proposed scheme can reduce total investment costs by 5,288 kCNY and 4,581 kCNY compared with the two existing schemes, while maintaining power supply reliability, demonstrating the effectiveness and economic advantages of the HCTPSS.