An evaluation of selected solid-state transformer topologies for electric distribution systems

Multiple topologies of solid-state transformers (SST) were proposed for locomotive traction systems, and more recently, for electric power distribution systems because of advantages such as reduced volume and weight, and functionalities not always possible with traditional fundamental-frequency transformers. The main goal of this paper is to evaluate selected SST topologies based on dual-active bridge (DAB) converters as well as a new SST topology based on boost converters in order to establish their suitability for emerging applications in electric power distribution systems. The evaluation is based on the number of power semiconductor devices, requirements imposed upon the high-frequency (HF) transformers, system losses, and a simplified cost comparison. The new boost-based SST topology has the highest system efficiency among the evaluated topologies, but requires twice the number of power semiconductor devices when using the same high-voltage device in all topologies.