An ISOP Hybrid DC Transformer Combining Multiple SRCs and DAB Converters to Interconnect MVDC and LVDC Distribution Networks

A hybrid dc transformer (DCT) combining multiple series resonant converters (SRCs) and dual-active bridge (DAB) converters with input-series-output-parallel (ISOP) configuration is proposed in this article. The proposed DCT is suitable for connecting medium-voltage dc and low-voltage dc distribution networks, which combines SRCs as the majority modules for power transmission and DAB converters as the minority modules for terminal voltage regulation or power regulation. Benefiting from the hybrid circuit topology, the proposed DCT can achieve a higher efficiency than the ISOP DAB converters with a reduced complexity in the communication and control, while maintaining the controllability of the dc voltage/power. The operation principles of the proposed DCT are analyzed and key parameters design are presented. Then, a 1 MW, 10 kV/750 V hybrid DCT is simulated and a DCT prototype of 2 kW, 400/100 V is built to verify the theoretical analysis.