Real-time Simulation Platform for a Solid-State Transformer with Multilevel Cascaded H-Bridge Dual-Active Bridge Back-to-Back Converters

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 three-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 an SST is a key step to validate its design and control algorithm before moving to hardware development. However, simulating an SST in real-time is very challenging due to its complex topology with a large number of 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. To validate the development of the real-time simulation platform, an SST model was developed and tested. This design had a modular, multilevel, cascaded H-bridges and dual-active bridges in a back-to-back topology along with a hierarchical control algorithm. Simulation results show the stable operation of this SST topology for specific setpoint changes, thereby vetting the real-time simulation platform presented.