Resonant Commutation Technique for Scalable Electronic-Embedded Transformer DCX with Bidirectional Switch

Due to the galvanic isolation, fixed voltage ratio, and high efficiency, dc transformer (DCX) plays a significant role in the high-power applications such as data center power supplies, energy storage systems (EES), medium-voltage solid-state transformers (SST), and transportation electrification. To tackle the inherent trade-off between high power and high frequency in transformer design, the electronic-embedded transformer (EET) concept was introduced in [1], where semiconductor electronics are integrated into the transformer windings and a robust current sharing can be realized automatically without any feedback control. Based on this concept, this paper firstly simplified the EET topology with only one bidirectional ac switch. And then, a resonant commutation (RC) technique was developed to achieve a quasi-trapezoidal current through the transformer. Compared to the triangular current in typical EET-DCX [1], the rms current can be reduced. In addition to saving the device number, the proposed RC EET-DCX can retain the significant merits from resonant CLLC/LLC-DCX, such as load-independent voltage gain, and full load range zero-voltage-switching (ZVS). Finally, a 12 kW RC EET-DCX with four paralleling transformers was built to verify the aforementioned analysis.