AC-AC Solid State Transformer Based on Single Conversion Stage

Single phase solid state transformer (SST) has received great attention among researchers and engineers as an effort to replace the standard 50/60Hz low frequency (LF) transformer in certain applications where bulky and heavy low frequency transformer become prohibitive. The main challenge in SST research is how to achieve comparable efficiency and high reliability of the traditional LF transformer. The heavy and bulky low frequency (LF) transformer single phase (50/60 Hz) has long been a proven technology as a solution for providing power delivery in wide range of power rating and voltage rating. However, in applications where the physical dimension of transformer is a limiting factor for its utilization such as in aerospace application, solid state transformer (SST) becoming an interesting alternative to the LF transformer. To significantly miniaturize the physical dimension of the transformer, SST operates at high switching frequency by utilizing power transistor to convert the low frequency power into high frequency power which can be efficiently transferred with much smaller transformer. Based on that target, a single stage single phase SST was developed with separate high frequency converter link (HF-Link) and low frequency commutation bridge (LF-Bridge). The HF-Link was realized using full bridge converter. In this project, our experience in developing single phase SST will be presented along with the lesson learned during the development. A converter structure based on separate high frequency converter link and Low Frequency Commutation Bridge was studied, tested, and analyzed. From the experimental measurement, the prototype converter was able to provide clean sine wave power to the load with conversion at the 1kW maximum load.