A Quad-Active Bridge (QAB)-Based Solid-State Transformer for Fast Charging of Light/Medium and Heavy Electric Vehicles

Integrating electric vehicle (EV) fast charging stations with the medium voltage (MV) grid using a solid-state transformer (SST) has attracted more interest from researchers due to the reduced size and the smart functionalities it offers for maintaining the stability and power quality of the grid. However, the modular structure of SST requires many power converters and high-frequency transformers in the isolated DC/DC converter stage which again increases the space of the charging station. This paper proposes a design of an SST-based EV charging station using a quadruple-active-bridge (QAB) as the isolated DC/DC converter and investigates the power density enhancement compared to the dual-active-bridge (DAB)–based system. The proposed charging station can charge different EVs with different battery voltages (800V, 400V, and 200V) and capacities. The performance is validated by simulating a 1MVA, 10kV EV charging station using MATLAB. The control architecture and a detailed analysis of the system are included in the paper.