Direct power control of dual-active-bridge dc–dc converters based on unified phase shift control

摘要

Dual-active-bridge (DAB) dc–dc converters are the important part of the transformerless electric traction drive system in railway application. Also the dynamic characteristic of DAB converters in the electric traction drive system is very significant under the input voltage fluctuation. In order to improve the efficiency and enhance the input voltage step response, a direct power control with current-stress-optimised (DPC-CSO) method based on unified phase-shift control for DAB converters is proposed in this study. Compared with traditional current-stress-optimised scheme, DPC-CSO scheme can reduce current stress of switching devices and improve efficiency further. Meanwhile, it can keep the output voltage constant when it faces with the input voltage step-change. In addition, only two voltage sensors are used in DPC-CSO scheme to reduce system cost. Finally, a scale-down DAB converter experimental platform is developed, and the experimental results have verified the excellent performance of the proposed DPC-CSO scheme and correctness of theoretical analysis.