Modular converter architecture for medium voltage ultra fast EV charging stations: Dual half-bridge-based isolation stage

The concept of ultra fast charging of Electric Vehicles (EVs) is expected to contribute significantly to their widespread utilization in long-distance travels. Towards this direction, emerging power electronic topologies will be the key components of the developed charging infrastructures. Lately, a novel converter architecture has been proposed for such a purpose. The latter is based on a Cascaded H-Bridge (CHB) converter with integrated battery energy storage systems, which play the role of a buffer in such a power demanding application. This paper is focusing on the isolated DC/DC conversion stage, which is needed for the achievement of the high charging currents. The dual half-bridge (DHB) converter is chosen, which fulfills several requirements for the studied application. The soft switching operation of the converter under wide input-output voltage variations is discussed. Moreover, a current controller is designed, capable of dealing with the topology-specific challenges. Finally, the development of a down-scaled laboratory prototype is described and experimental results are provided.