Three-phase dual active bridge converter design considerations

In three-phase dual-active-bridge (DAB) converter, the zero-voltage-switching (ZVS) range, DC capacitor ripple current and converter efficiency are significantly impacted by the selectable system parameters, including transformer turn ratio n, switching frequency f and leakage inductance Lk. The converter performance also varies with different operation conditions, i.e., input voltage, output voltage and output power level. Therefore, these parameters need to be carefully selected to achieve optimized performances. In this paper, a comprehensive study of the parameter selection for the three-phase DAB converter is conducted under different operation conditions. A new parameter fL is defined to reduce the analysis from 3 dimensions to 2 dimensions, which simplifies the analysis of transformer turn ratio significantly. Furthermore, the effective operating area (EOA) of f and Lk are defined for feasible transformer designs. The current stress of switches and DC capacitors are studied in the EOA to help determine the range of f and Lk. Finally, the converter total loss and efficiency are analyzed at full and half load with different input and output voltages. The converter parameter (n, f, Lk) can be selected using ZVS and efficiency criteria. The tradeoff between high efficiency, wide ZVS area and low capacitor ripple current can be achieved accordingly.