Objective In urban rail transit traction power supply systems, the topologies and control methods of different power supply equipment affect the system energy consumption. To clarify the system-level energy-saving effect of the full bi-directional converter power supply scheme compared with the conventional rectifier unit plus inverter-based feedback device, it is necessary to perform a comparative analysis.

Method Efficiency models and equivalent-circuit models for key substation equipment are developed, and AC/DC transmission-loss models of the power-supply system are established. A system-level traction energy consumption evaluation index is proposed to individually quantify energy consumption segments, such as train traction energy, main substation reverse power consumption, device losses, and AC/DC transmission losses. Taking an under-construction subway project in Qingdao as an example, a simulation-based comparative analysis is conducted under identical control objectives and capacity configurations, to study the energy-saving effects of the full bi-directional converter power supply scheme and the conventional rectifier unit plus inverter-based feedback device power supply scheme.

Result & Conclusion  The metered energy consumption at the main substation for the bi-directional converter power supply scheme is 12 558.05 kWh, lower than the 12 573.95 kWh for the conventional rectifier-inverter power supply scheme, improving the overall energy-saving rate by 0.27%. Although the efficiency of the bi-directional converter itself is slightly lower, and device losses increase due to the higher device start-stop frequency, its constant-voltage control decreases the DC-side transmission losses and the main substation reverse power consumption, thereby lowering the total system energy consumption.