Hybrid modulation strategy of three-phase dual-active-bridge converter to improve power conversion efficiency under light load conditions in LVDC applications

Abstract

A hybrid control strategy for the three-phase dual-active-bridge (3P-DAB) converter of LVDC applications is presented to improve the power conversion efficiency under light load conditions. The 3P-DAB converter is an attractive topology for high-power applications such as railway traction and aircraft due to its inherent the zero voltage switching (ZVS) capability and reduction of conduction loss due to an interleaved structure with seamless bi-directional power transitions. However, conventional phase shift modulation (PSM) applied to a 3P-DAB converter has disadvantages such as ZVS failure under light load conditions. In this paper, an asymmetrical pulse width modulation is inserted into PSM to replace the existing modulation algorithm of a 3P-DAB converter with a simple control approach. In the proposed control, the transferred power can be calculated according to the mode changes. In addition, the soft switching area of the power switches can be expanded by the proposed hybrid control strategy. Finally, experimental results validate the proposed hybrid modulation strategy using a 3-kW prototype 3P-DAB converter.