A bi-directional DC-DC converter with overlapping input and output voltage ranges and vehicle to grid energy transfer capability

A bi-directional buck-boost DC-DC converter is presented for vehicle charging as well as vehicle to grid (V2G) energy transfer. The chosen cascaded buck-boost topology allows overlapping input and output voltage ranges and a higher intermediate DC bus voltage where the electric drivetrain traction inverter can be connected. The intermediate DC-link capacitor voltage is varied to improve the transient performance of the converter. The reference voltage of this capacitor is set based on the input and output voltage levels, and the power demand. Experimental results have shown that with its modularity, control flexibility and transient performance the converter is a viable candidate for vehicle-to-grid energy transfer.