Analysis of Magnetic Configurations to Enhance DAB Converter Performance Over a Wide Power Range at High Voltage

Abstract

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.