A Novel Urban Rail Transit Full DC Flexible Power Supply System

Urban rail transit plays an important role in reducing road congestion and greatly facilitates travel. Currently, reducing energy consumption and implementing high-quality power supply are two urgent needs of urban rail transit power supply systems. Therefore, this paper presents a full DC flexible power supply system in which the DC standard is adopted for the medium voltage power network, traction network, and station low-voltage distribution network. A modular multilevel converter (MMC) is deployed in the main substation to supply a medium voltage power network. Moreover, the traction and step-down substations in the traditional DC power supply system are merged to form a secondary substation. The three-port energy router based on the dual active bridge (DAB) DC‒DC converter simultaneously connects the medium voltage power network, traction network, and station distribution network. On this basis, via the power allocation of a comprehensive energy management system, the regenerative braking energy can be efficiently utilized. Finally, simulation tests are implemented to validate the correctness and superiority of the proposed system.