Resonant Commutation Electronic-Embedded DC Transformer (RC-EET DCX) With Quasi-Trapezoidal Current and Natural Current Sharing

High-power and high-density dc transformers (DCXs) are critical components in data center power supplies, energy storage systems, medium-voltage solid-state transformers, and transportation electrification. The challenges associated with designing high-power and high-frequency transformers are considerable. The electronic-embedded transformer (EET) concept, proposed in Cao et al. (2023), is a response to these challenges, integrating semiconductor electronics into the transformer windings. In light of this concept, this article presents two significant modifications. First, it replaces the complete full bridge with a low-voltage bidirectional ac switch. Second, it introduces a resonant commutation (RC) to realize a quasi-trapezoidal transformer current with a smaller rms value. Compared to the triangular current produced by the original EET-DCX in Cao et al. (2023), the rms current can be decreased by 15%. In addition to streamlining the circuit, the proposed RC EET-DCX retains all the advantages of the original EET-DCX, including simple open-loop control and natural current sharing. By incorporating only one embedded bidirectional ac switch, the impedance of the high-frequency transformer leakage inductance is fully neutralized. As a result, the rated power of the proposed RC EET-DCX can be readily scaled up through transformer-level parallelism. Furthermore, the RC EET-DCX maintains the benefits of typical LLC/CLLC-DCX, including load-independent voltage gain, full load range zero voltage switching, and low circulating current. To verify aforementioned benefits, a 12-kW RC EET-DCX with four planar RC EET units was built and tested.