Fundamental Duty Modulation of Dual-Active-Bridge Converter for Universal Reduced Conduction

This paper proposes a modulation scheme for a dual-active-bridge (DAB) converter to reduce current conduction in wide-range operating conditions. The operating principle of the proposed fundamental duty modulation (FDM) is formulated based on the fundamental component analysis (FCA) of the DAB converter. By modulating the PWM signals in the fundamental component domain, the circulating current can be reduced to the minimum level. With the proposed FDM, the controller implementation can be much simpler than the other conventional modulation schemes maintaining high efficiency especially at light load condition. The proposed scheme features smooth transitions against load change since it does not require an operating mode classification or off-line calculations. Furthermore, the proposed method does not require current information. The experimental results for verification of the proposed modulation scheme show efficiency improvements and smooth transient responses.