Energy-efficient train control for metro considering the power propagation in the traction power supply system

When optimizing driving strategies of metro with the target of reducing energy consumption of the substations, traditional methods require frequent power flow calculations of the traction power supply system (TPSS), which inevitably leads to a dramatic increase in computational time. In this paper, we define an external power for metro based on the principle of maximizing the utilization of other trains output power during its propagation in the TPSS, which can be predicted prior to optimization. Consequently, we obtain the quasi-optimal solution to the original problem indirectly by solving the energy-efficient train control (EETC) problem considering the external power utilization. For this new EETC problem, we propose three fundamental optimal control strategies for metro and develop numerical algorithms. The results are compared with the optimal solution obtained through three-dimensional dynamic programming which directly addresses the original problem. The comparison demonstrates that while achieving comparable energy-saving performance, our proposed method can reduce computation time from hours level to seconds level.