Modeling and Control of the Asymmetric Multiport Solid-State Transformer for High Power Charging

This paper introduces a novel Asymmetric Multiport Solid-State Transformer (AMP-SST) topology based on a cascaded H-bridge converter, with switching cells incorporating Dual Active Bridges. The proposed architecture enables the direct, galvanically isolated connection of multiple EV charging stations to the MV-AC grid. The use of asymmetrical groups of cells at each charging port increases the permissible power imbalance within the converter while maintaining a symmetrical threephase grid current. To ensure stable operation of the converter, the permissible power unbalance is determined by modeling the steady state. The proposed real-time control strategy facilitates independent output power control of each port and manages the cell voltage balancing under varying load scenarios. The stable operation and control concept of the proposed AMP-SST is experimentally validated using a low voltage prototype.