A novel traction power supply system for urban rail transportation

This paper presents the design of a novel traction power supply system for urban rail transportation based on multiple-paralleled H-bridge modules. A quasi-sinusoidal voltage output is generated by the novel system with phase-shift control mechanism and the voltage combination of the zig-zag connected transformers on AC line side. As a result, the harmonic components on line side can be greatly eliminated resulting in a higher power factor. Moreover, the power flow of the novel system is bidirectional and the power generated during the braking of vehicles can be fed back into the AC electric grid, saving much of it.