A Bi-directional Three-phase Y-Y CLLC Resonant Circuit with Adjustable Bridge Arms applied to a Wide Output Range

This paper proposes a bi-directional three-phase Y-Y CLLC resonant circuit topology with adjustable bridge arms for a wide output range DC-DC converter. Its primary objective is to improve the poor output voltage regulation under light load conditions and enhance efficiency under medium to heavy load by switching the bridge arms of the three-phase Y-Y CLLC resonant circuit between three-phase, full-bridge, or half-bridge modes. This paper mainly presents an introduction to the topology, adjustable bridge arms, circuit switching analysis, gain calculation, mode switching, and loss analysis. Finally, a $1.5 \mathrm{~kW}, 400 \mathrm{~V}_{\mathrm{DC}}$ input, and 150-450 VDC output bidirectional three-phase Y-Y CLLC resonant converter with adjustable bridge arms is developed, achieving a maximum efficiency of $\mathbf{9 5. 2 \%}$. Keywords-three phase Y-Y, CLLC, wide output range, adjustable bridge arms, resonant converter