This article discusses the various ways in which the stresses experienced by the IGBTs and diodes in a Dual Active Bridge (DAB) are asymmetric. This asymmetry can be between the two bridges or between IGBTs and diodes on both bridges. The terminal voltage, transformer ratio and the power through the DAB are varied to discuss the stresses. These asymmetrical stresses lead to devices' distinct temperatures. This unevenness of stresses can affect the lifetime of the devices employed. An analytical model of the DAB is used to analyse the currents and power losses in various devices. Some preliminary results of power losses in the devices are presented.

The Dual Active Bridge (DAB) is a popular DC-DC converter for bidirectional power transfer in applications such as the re-emerging technology of flow batteries. For such applications, it is essential to design the DAB for the wide voltage range operation of batteries, specifically focusing on its non-linear characteristics. The existing design methods utilise an optimisation algorithm to minimise the losses of the DAB at various equidistant voltage points in the voltage range. The resulting design is less efficient as it gives too much weight to insignificant operating points. This article proposes a new method that uses the flow battery characteristics to determine the operating points at which minimisation should be performed. The proposed method is validated with simulation results.