A Prodrive-led consortium managed to run a silicon carbide-based multiport DC-DC converter in an electric car. The converter – which controls power flow between multiple energy sources -- has managed to return a class leading efficiency of 98.7%. This was achieved while increasing power density and cutting the converter’s size and weight.
The DC-DC converter serves as a hub that could transfer energy between key components of a car’s high voltage electrical system. The converter features four ports, two of which link to the traction motor and high voltage battery.
The third port links to a secondary energy source (super capacitor bank) while the fourth port provides power to the EV’s 12V systems. The DC-DC converter could match the voltages of the components as well as transfer energy between them when prompted by CAN commands from an external supervisory controller.
The converter was tested in a Tata Vista EV demonstrator vehicle with a 220V battery and 37kW traction motor. The EV features two 200 kJ super capacitor banks that run at 75-150 V.
Mark Willows, Prodrive electrical systems and control specialist, remarked that in normal driving, the DC-DC converter increases the battery voltage to about 400 V for an optimal motor performance.
He added the converted can supplement the battery supply with additional energy from the super-cap banks when the driving situation calls for it. The DC-DC converter transfers energy during re-generation from the motor to the battery or super-capacitor banks, as commanded by through supervisory controller.
The converter could also transfer energy directly between the battery and super capacitor ports. The system could also be configured to support other energy sources like fuel cells. It could also be configured to supply multiple traction motors.
The converter uses silicon carbide devices that could operate at a higher frequency than silicon components. It also results to lower switching losses and smaller magnetic components, enabling the converter to achieve an efficiency of 98.7%, a gravimetric power density of 10.5kW/kg and a volumetric power density of 20kW/liter. [source: Prodrive]