Determination of the Optimum Transformation Ratio for a Trapezoidal Modulated Dual Active Bridge Converter for Wide Range Voltage Operation

This paper provides analytical approaches for determining the optimum transformation ratio (TR) of a trapezoidal modulated dual active bridge (TraMDAB) converter for automotive and other related applications. The approaches are based on the duty cycle of the transformer (inductor) AC voltages. The search for optimum TR is explored further using the extrema of the converter's maximum power transfer. The theory is verified by simulation of a 5 kW TraMDAB converter modelled in PLECS. The converter was operated at 50 kHz for an input voltage range of 500 V to 1000 V and output voltage range of 10 V to 15 V to determine the best choice among the three investigated TRs selected based on the limit provided by this paper. It concludes that the selected TR must not be too close to or not far from the maximum allowable TR such that the required voltage and power ranges are covered. The resulting transformer must be easy to manufacture, and its size must not impact negatively on the converter's power density. A modified leakage inductance formula is provided to limit the output power to the specified power range.