Switching Modulation Method for Current-Fed Dual-Active-Bridge Converter to Improve Power Conversion Efficiency

A current-fed dual active bridge (CF-DAB) converter has attracted much attention in battery applications and energy storage systems (ESS) because of their zero-voltage-switching (ZVS) capability and high performance due to the high control degree of freedom. However, conventional switching algorithms cannot reduce the high current in low-side switches under the heavy load condition. It causes high conduction loss which decreases power conversion efficiency. In this paper, a new switching modulation method of the CF-DAB converter for the ESS application is proposed to improve the power conversion efficiency by reducing the conduction loss. The relationship between the pulse width modulation (PWM) and the phase shift modulation (PSM) is investigated and a PWM-plus-PSM modulation method is proposed to reduce the conduction loss. A 1-kW prototype CF-DAB converter is used to verify the effectiveness of the proposed switching modulation method.