Under the background of achieving the dual carbon goals, urban rail transit needs to achieve energy-saving and low-carbon operation. The existing traction power supply system (TPSS) with droop control strategy has some problems, such as low utilization rate of regenerative braking energy, lack of proactive and effective control and optimization measures for power flow. This paper analyzes the impact of droop parameters of the bidirectional converter on the power consumption of the system, and then proposes a collaborative control method to achieve optimal distribution of traction load power. This method optimizes and adjusts droop parameters of the bidirectional converter in real-time, which promotes the flow of regenerative braking energy, and realizes the real-time control of system power flow. Simulation calculations demonstrate that this method can save 17 million kWh of electricity per year and effectively contributing to the safe and economical operation of the TPSS of urban rail transit.