Timetable optimization for maximization of regenerative braking energy utilization in traction network of urban rail transit

Timetable optimization is one of the effective solution methods for urban rail transit to achieve energy-saving. Previous studies on timetable optimization only focused on the transfer and utilization of mechanical energy, which did not consider the exchange of energy and line losses in the traction network. Therefore, this paper constructs a cross-substation energy transmission and utilization model taking into account the characteristics of the actual traction power supply systems. An overlap current method is presented to increase the utilization of regenerative braking energy (RBE) of trains and reduce the energy supply of the traction substation by considering the line loss, which is achieved by compensating the current generated by accelerating and braking trains in the substation. The compensation current can be maximized by adjusting the dwell time to achieve energy-saving. The traction power supply systems with highly nonlinear dynamic characteristics are linearized to construct a mixed-integer linear programming (MILP) model, which utilizes the utilization of RBE as the objection and dwell time as the variable. The method of maximum compensation current is verified by numerical examples based on Beijing Batong Line. The results show that the energy-efficient of the method is greatly improved compared with the method of maximizing the overlap time between the accelerating train and the braking train.

Automated summary

Timetable optimization is an effective solution to achieve energy-saving in urban rail transit. Previous studies neglected the energy exchange and line losses in the traction network, focusing only on the transfer and utilization of mechanical energy. This paper proposes a cross-substation energy transmission and utilization model considering the characteristics of actual traction power supply systems. A method for increasing the utilization of regenerative braking energy and reducing energy supply by compensating the current generated by accelerating and braking trains is presented. By adjusting the dwell time, the compensation current can be maximized, resulting in energy-saving. A mixed-integer linear programming model is constructed to linearize the highly nonlinear dynamic characteristics of the traction power supply systems, with the utilization of regenerative braking energy as the objective and dwell time as the variable. Numerical examples based on Beijing Batong Line verify the effectiveness of the method, showing significant improvement in energy efficiency compared to maximizing the overlap time between accelerating and braking trains.