Wide range ZVS operation of dual active bridge DC-DC converters using adaptive modulation and low coupling factor transformers

One of the central requirements of a Dual Active Bridge (DAB) converter is to operate under Zero Voltage Switching (ZVS) conditions, to reduce switching losses and increase operating efficiency. This paper shows how frequency domain analysis can be used to design and operate a DAB to ensure ZVS across the entire operating range by using transformers with a reduced winding coupling factor and adaptive 3-level bridge modulation, while also including second order effects. The approach is shown to achieve experimentally measured efficiencies between 96.5% and 98.5% over the entire power range for an optimised DAB converter stage (>1 kW).