Power Quality Enhancement of Dual Mode Traction Power Supply System Based on Power Hub

In order to solve the problems of AC negative sequence (NS) and DC traction network voltage fluctuation in dual mode traction power supply system (TPSS), this study proposes dual mode TPSS based on power hub. It can fully compensate AC NS by co-phase power supply technology. Furthermore, it integrates coordinated power flow management among the AC grid, DC traction network, and energy storage system, enabling both efficient utilization of regenerative braking energy (RBE) and peak load shaving, thereby effectively stabilizing DC link voltage fluctuations. Consequently, an overall control strategy with a hierarchical structure is developed. In the upper layer, a cooperative compensation algorithm with constraints of AC NS and DC traction network voltage is designed to calculate the port compensation power. The lower layer ensures stable system operation and precise compensation by controlling multiple converters in accordance with upper-layer commands. The experimental results show that the VU is compensated to close to 0 and the DC voltage is stable in the safe range under different operating conditions.