Single Phase 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 (>98%) and high reliability of the traditional LF 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 SRC converter and the LF-Bridge was realized with two full bridges to perform the bipolar to unipolar folding and the unipolar to bipolar unfolding. In this paper, 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 efficiency at 94.65% at the 3kW maximum load.