Y-Δ結線による三相絶縁型双方向DC/DCコンバータの軽負荷時の効率改善

概要

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In order to improve light-load efficiency, a Y-Δ connected three-phase dual active bridge (DAB) galvanically isolated bidirectional dc/dc converter topology is proposed in this paper. All the primary and secondary switches of this converter are operated in a soft-switched manner over the entire operating range, when the secondary to primary voltage gain is kept within approximately 100 ± 14%. In comparison with the conventional Y-Y connected three-phase DAB converter, the stresses of power devices such as transformers, inductors, filters' capacitors, and switches are almost at the same level as that of the conventional converter, and the power devices can be kept at the same size. With space vector analysis of voltage harmonics and inductor current harmonics, it is clear that the 5th and 7th harmonics' reactive current flowing through the inductor is greater than that of the Y-Y connected DAB converter at light-load condition, which makes switches easy to be operated in a soft-switched manner when they turn on. A 5.5kW prototype has been built to verify all the theoretical considerations.