Design strategy and simulation of medium-frequency transformers for a three-phase dual active bridge

Transformers are key elements in high power dc/dc converters such as the dual active bridge. Special attention is required because the dc-to-dc technique operates with non-sinusoidal voltages and currents. Therefore, iron and copper losses differ when compared to standard ac (sinusoidal) operation and sinus based design rules are no more suitable. The working principle of a dual active bridge (DAB3) relies on a particular value of leakage inductance to control the power flow. This inductance can be realized by the sole leakage inductance of the transformer or by connecting an additional choke inductance. The present paper shows the results obtained using an evolutionary strategy applied to design a transformer. The algorithm is adjusted to the particular conditions of the converter such as the flux density waveform (DAB3). The integration of the inductance can be performed by the design strategy and the design is compared to the external choke inductance solution. At this stage of work, the overall test bench setup is verified using simulations.