A New Asymmetric Leakage Inductance for Enhancing Zero-Voltage Switching Performance in Asymmetric Triple-Active-Bridge Converters

The triple-active-bridge (TAB) converter is a representative topology that seamlessly integrates dc sources and loads with galvanic isolation. Especially, there is a growing demand for an asymmetric TAB converter that provides distinct nominal powers at three ports, particularly in electric vehicles and power distribution systems. From the perspective of converter design, the leakage inductance is significant because it is related to zero-voltage switching (ZVS) of switches, and finally affects the power efficiency. Previous articles did not consider the asymmetric TAB converter and a clear guideline of designing leakage inductance for it has not been presented. In this situation, this article proposes a new method for determining leakage inductance for the asymmetric TAB converter. By using the proposed method, the ZVS regions in all power flow conditions are extended up to 62% more than those of the conventional method. Consequently, switching losses under light-load conditions are significantly reduced, enabling the converter to attain high power efficiency in a wide range of power conditions. The unified expression of asymmetric leakage inductance is addressed through the delta equivalent model of the TAB converter, and the comprehensive analysis of ZVS is discussed. The effect of the ZVS region extension with the proposed method is verified by comparing the ZVS regions between the conventional and proposed configurations. Through the simulation model of high-power scale, switch losses are estimated in various power flow conditions, validating the feasibility of the proposed method in practical industrial applications. The performance of the proposed method is finally demonstrated through a 3 kW reduced-scale TAB converter.