Application of Bidirectional Converters in Urban Rail Transit Power Supply Systems

Abstract

[Objective] To address the challenges about renewable energy utilization and significant grid voltage fluctuations in urban rail transit power supply system, a power supply solution based on bidirectional converter technology for traction system is proposed. [Method] The main circuit topology and operational logic of bidirectional converters are introduced. The control characteristics of bidirectional converters under two operating modes of independent power supply and hybrid power supply are presented, and the external characteristic curves combining constant voltage and droop are designed. Using the example of Xuzhou Metro Line 2, tests are conducted for both independent power supply and hybrid power supply under traction and braking conditions for a single train AW0 (unloaded) on the depot test track. Same tests are also performed under normal operation conditions with 12 trains on the mainline. Performance indicators for train operation and bidirectional converters are evaluated. [Result & Conclusion] Bidirectional converters can automatically and smoothly switch between rectification and inversion modes based on the train on-line operation conditions, automatically adapting to the train traction/braking conditions. The use of bidirectional converters in power supply significantly ameliorates train grid voltage fluctuation, preventing working conditions below 1 500 V and enhancing train traction characteristics.

Keywords

• urban rail transit
• power supply system
• bidirectional converter