T09.8 - A Partial-Power-Processed CLLC-Dab DC/DC Transformer with Voltage Self-Balancing Capability for Bipolar LVDC Distribution Systems

The bipolar low-voltage DC (LVDC) distribution system is an excellent approach to facilitate the flexibility and reliability of the DC microgrids. This paper proposes a DC-DC transformer with bipolar multi-voltage output and self-balancing property. First, this configuration combines the efficient CLLC converter and the flexible DAB, with the main power transferred via the CLLC converter and the DAB carrying partial power. Moreover, for achieving self-balancing, a pair of resonant LC branches are implemented on the secondary side of the CLLC and DAB converters, forming a new series resonant dual-active-half-bridge (SR-DHB) converter that enables partial self-balancing. Additionally, following the principle of volt-second balancing, inductors and capacitors can be added to the first arm, completing the self-balancing property. Furthermore, precise regulation of the output voltage can be achieved by merely adjusting the phase shift angle of the DAB. Lastly, simulations reveal outputs of 750V and 375V, and experiments is conducted to prove the proposed scheme.