Priority-Based DC-Link Voltage Control for Railway Traction Chains With Onboard Energy Storage

Due to the rapid development of power electronics and energy storage technologies, the trend toward electrified railway systems with onboard energy storage systems (OESS) is being followed by main train manufactures. In such systems, the control of the dc-link can be critical for stability and optimal power sharing between different energy sources. This paper presents a dc-link control strategy intended for OESS-based traction chains. A distinguishing characteristic of the proposed method is its ability to smoothly share the power demand among the available power sources, including the kinetic energy of the train, based on predefined priority levels. The control smoothly reacts to changes in the power limits, including no power, of the available energy sources, without modifying the control structure and with negligible variations of dc-link voltage. Simulation results are provided using a real train model with an onboard battery system. Finally, the proposed control is validated on a hardware prototype.