Objective With the continuous expansion of line network scale, the significant electricity consumption issue caused by urban rail transit system cannot be ignored. Train diagram is a crucial factor influencing the traction energy consumption of the system. It is necessary to carry out a research on energy-oriented train diagram to reduce the system traction energy consumption.

Method Based on the negative correlation between inter-section running time and train traction energy consumption, and the principle of regenerative braking energy utilization, a two-stage optimization method for energy-oriented diagram is proposed to minimize net traction energy consumption. In the first stage, based on the pre-stored multi-operation level information in the ATS (automatic train supervision) system, a diagram scaling optimization model is established to minimize the turnaround traction energy consumption, thus achieving the effective allocation of train inter-section running time. In the second stage, a mixed-integer nonlinear programming model is constructed with train headways as the decision variables, aiming to maximize the overlap time of traction and braking trains near the same station. The model is then further processed into a linearized form for easier solution. A case study is conducted using an actual metro line in China, and the commercial solver GUROBI is used to solve this model.

Result & Conclusion  The first stage optimization reduces the train turnaround traction energy consumption from 650.30 kWh to 593.55 kWh, achieving a reduction of 8.73%, while keeping the total train turnaround time unchanged. The second stage optimization further increases the overlap time of traction and braking trains from 1 005 seconds to 1 710 seconds, representing an increase of 70.10%. The proposed method achieves a dual optimization of both train turnaround traction energy consumption and regenerative braking energy utilization rate, thereby enhancing the energy-oriented performance.