The challenges of determining the optimum transformation ratio for a triangular modulated dual active bridge converter

This paper identifies the challenges of determining the optimum transformation ratio (TR) for a triangular modulated dual active bridge converter (TMDABC) applicable for a wide voltage range TMDABC for automotive applications. Duty-cycle-based methodology is developed which shows the restrictions imposed on the TR by the choice of the PWM implementation. The optimal choice of the ratio is considered via transferred power maximisation. A TMDABC is configured in PLECS to verify the method. The DAB converter was operated at 50 kHz within an input voltage range of 100 to 1000 V and output voltage range of 8 to 16 V, providing an output power of 5 kW. Within the threshold of the recommended range of acceptable TRs, the simulation result shows the secondary side RMS current ranges of 388 – 812 A, 435 – 787 A, 464 – 768 A for TRs 5, 4, and 3 respectively compared with 510 – 917 A obtained through the choice TR outside the allowable threshold. The selection approach has potency to reduce current stress and reduce conduction losses (improve efficiency).