A Bidirectional DC-DC Converter With Overlapping Input and Output Voltage Ranges and Vehicle to Grid Energy Transfer Capability

A bidirectional buck-boost dc-dc converter and its control is presented for vehicle charging as well as for vehicle-to-grid energy transfer. The 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 performances of the converter. The reference voltage of this capacitor is set based on the input and output voltage levels, and the power demand. The modularity, control flexibility, and excellent transient performance of the converter have been verified with simulation and experiments.