Control of a Modular Multiport Solid State Transformer for a Flexible High Power Charging Infrastructure

This paper presents a control strategy for a Multiport Solid-State Transformer designed to connect multiple EV charging stations to the medium-voltage AC grid. The transformer employs a Cascaded H-Bridge converter composed of identical switching cells, each incorporating a Dual Active Bridge to provide galvanic isolation between the AC grid and the charging ports. Steady-state modelling of the multilevel converter is used to identify the permissible power imbalance between charging ports, ensuring stable operation. The proposed real-time control method facilitates independent output power control for each port while maintaining effective cell voltage balancing across the converter. Furthermore, dynamic switch matrix reconfiguration enhance the converter’s operational range. The control strategy is validated through simulations and experimental measurements, demonstrating improved flexibility and performance for scalable EV charging infrastructure.