In dual active bridge (DAB) converters, the external series inductor is often placed on the high-voltage side to reduce its losses, but in this configuration, the transformer magnetizing inductance is excited by the reflected voltage of the low-voltage port. This configuration can lead to higher transformer core losses for the DAB converter. However, in a split inductor configuration, the magnetizing current is supplied by both the high-voltage and low-voltage side bridges, reducing the volt-seconds across the magnetizing inductance and therefore reducing core losses. In this work, an analytical expression for the transformer magnetization voltage is presented, and the reduction in transformer core loss achieved by using a split inductance configuration is calculated. An 11kW, 775V/450V prototype is implemented, and both magnetic configurations are experimentally compared under identical volume and thermal conditions for a wide power range at 450V. Under steady-state thermal conditions at 450V and 11kW, the split-inductance configuration achieves up to a 5.88% reduction in total converter losses and an 18.3°C decrease in the worst-case transformer core temperature compared to the high-voltage-side inductance configuration.

In dual active bridge (DAB) converters, series inductor and transformer functionalities are integrated into a single magnetic core structure to improve efficiency or power density. Allowing independent tuning of this integrated series inductance and magnetizing inductance gives higher design flexibility. However, the existing integrated magnetic methods often lower magnetizing inductance, compromise the transformer winding coupling, require complex custom core designs, or cannot effectively decouple transformer and inductor fluxes in the case of separate transformer and inductor windings. To overcome these problems, this article proposes a unified core structure that allows independent tuning of series inductance without the above-mentioned limitations. To demonstrate the performance of the proposed integrated structure, a DAB converter for a dc–dc electric vehicle charging application is built, and the proposed integrated structure is compared with discrete transformer and inductor structures under identical core volume and thermal steady-state conditions. It is experimentally validated that for the proposed structure at a high output voltage and high load conditions of 450 V and 9 kW, the magnetic power loss reduction is 8.8%, whereas, at a low output voltage and high load conditions of 250 V and 7 kW, the magnetic power loss reduction is 13.0%. Furthermore, this article presents an iterative design methodology based on the derived reluctance and analytical models to systematize the design process.

In a dual active bridge converter, the split series inductance configuration with finite magnetizing inductance can provide an additional degree of freedom to optimize the converter's performance. However, this magnetic configuration results in three separate magnetic structures, which increases the volume and footprint. To address this issue, this article proposes a four-winding integrated magnetic structure comprising decoupled primary inductance, secondary inductance, and a transformer capable of independent tuning. The fluxes produced by primary and secondary inductors within the integrated structure consistently oppose in the middle leg of the inductor core, resulting in reduced losses and a smaller volume. A design methodology based on an analytical model has also been developed to systematize the design process. A sensitivity analysis is performed using the finite element method to verify the decoupling operation. An 11 kW, 775 V/450 V prototype is implemented, and the integrated magnetic structure is compared with its discrete implementation under steady-state thermal conditions at different ambient temperatures. A volume reduction of 12.1% and magnetic loss reduction of 4.5% is achieved, while the converter efficiency remains higher or comparable to that of the discrete implementation across the entire operating range.

This paper compares the indirect cooling method using a heatpipe and air-cooled circular fins with conventional cooling methods like forced air convection and forced water convection for cooling power electronics placed underground. A two-module dual active bridge power converter with reconfigurable outputs for electric vehicle charging is used for the thermal analysis. The comparison is based on specific constraints imposed by semiconductor switch surface area requirements and the maximum junction temperature limit. A detailed analysis is presented, and performance parameters like convective resistance, pressure drop, and mechanical pumping power of the cooling systems as the function of volume flow of working fluid are obtained. Commercially available cooling components like extruded fin heatsinks, cold plate, and heat exchanger are used for conventional cooling methods analysis. Whereas indirect cooling using heatpipes and air-cooled circular fins is designed by performing individual analysis on a heatpipe sizing, air-cooled circular fin design, and heatpipe integrated base plate. This work also highlights the equivalent thermal resistance model for each cooling system.