Study on the start-up schemes for the three-stage solid state transformer applications

This paper investigates two stage-by-stage start-up schemes for a three-stage solid state transformer (SST) that includes a high frequency transformer. The DC-DC converter transformer current dynamics analysis presented in this paper shows that the stage-by-stage start-up scheme may lead to a relatively large transformer current. As a result, the DC-DC converter would suffer a relatively large input inrush current. The pre-charge start-up scheme can improve the transformer current profile during the transient. The detailed analysis of those two start-up scheme is presented and the experimental verification on laboratory prototype proved the analysis of stage-by-stage start-up scheme.