With the vast number of distributed energy resources integrated into the medium voltage distribution system, there is a strong need for flexible grid services to strengthen the grid's stability and reliability. The solid-state transformer (SST) can serve as an energy hub that provides grid services in the distribution network. The 3-stage SST has emerged as the most popular SST topology because of its flexibility, controllability, full isolation, and bidirectional power flow. Real-time simulation of SST is a key step to validate its design and control before moving to hardware development. However, simulating an SST in real-time is very challenging due to its complex topology with many power electronic switches involved. To address this challenge, a high-fidelity CPU-FPGA-based real-time simulation platform has been developed. Particularly, an FPGA-based model was developed with flexibility and scalability to simulate different SST topologies. An SST model with a modular, multilevel, cascaded H-bridges and dual-active bridges in a back-to-back topology was developed and tested. A hierarchy control algorithm was utilized in the simulation with pertinent simulation results presented.
