An Asymmetrical Phase-Shift Scheme of Three-Phase Dual Active Bridge With Minimum Current Root-Mean-Square Value Control

The three-phase dual active bridge (3ph-DAB) converter is a promising topology attracting increasing attention. However, because it is limited to symmetrical three-phase bridge control, the conventional single-phase-shift control method (SPS) remains the most common method for 3ph-DAB converter. The obvious shortcomings of SPS control include the soft-switching failure, massive circulating energy, and high root-mean-square (rms) current value at the light load, particularly with large voltage variation-ratio conditions. To overcome these drawbacks, this article proposes a novel asymmetrical phase shift (APS) control strategy. Unlike other optimized modulation schemes, this optimized strategy breaks the symmetrical control rules of three-phase bridges by introducing variable phase-shift angles among three-phase legs. The novel APS control strategy can substantially reduce the current's rms value and extend the soft-switching operation range due to these additional phase-shift angles. Further, the analytical solutions for the optimal phase-shift angles are derived by solving the global optimal condition equations. Analytical solutions, compared with complex numerical solutions derived by other optimized schemes, can be easily adopted in digital implementation and perform well under changing parameter conditions. Finally, experimental results verify the outstanding performance of the proposed modulation strategy.