Hybrid Resonant DC–DC Converters for DC Transformers in DC Distribution Networks With Limited Reverse Power Flow Range

In DC distribution networks integrating distributed generation, DC transformers (DCT) exhibit asymmetric forward and reverse power flows, with reverse power flow range being limited. Based on this characteristic, this paper proposes a hybrid resonant (HR) DC-DC converter for DCTs. Distinguished from traditional dual active bridge (DAB) converters and Hybrid Non-resonant (HNR) DC-DC converters, the proposed HR converter features a low-voltage hybrid resonant bridge composed of a low-voltage-side active bridge (LAB) and a low-voltage-side diode bridge (LDB) in parallel, enabling efficient adaptation to such asymmetric power flows. It not only satisfies power transmission requirements but also simplifies system complexity and reduces costs. Key technical aspects, including converter topology, operation modes, suppression of circulating currents in reverse mode, and impact of leakage inductance in high-frequency transformers, are analyzed in detail. Comparative studies show that the HR converter reduces semiconductor costs by 33.43% and conversion losses by 16.22% compared to DAB and HNR converters. Experimental results confirm the feasibility and performance benefits of the proposed converter.