A consortium of British companies, led by motorsport specialist Prodrive, is developing a new DC-DC converter for use in automotive hybrid and electric vehicles, which will be more efficient, smaller and lower cost than those currently available.
The project, part funded by the Technology Strategy Board under the technology programme (5th call – electrical/electronic control & power systems) will pool expertise from companies including Prodrive, HILTech Developments, International Transformers, LDV, Sloan Electronics and the Universities of Manchester and Newcastle.
Hybrids are powered by both small petrol or diesel engines and an electric motor. They also have the ability to capture the energy lost during braking to be reused later to power the electric motor, making them more efficient and less polluting than non-hybrid vehicles. Current hybrid vehicles without DC-DC converters compromise the energy storage device (usually ultra capacitors or batteries) and the electric motor. For example, when storing energy under braking, as the vehicle slows the voltage generated by the motor falls while the energy in the storage device increases. There is a point when the motor can no longer supply enough voltage for the storage device so energy recovery after this point is no longer possible. The situation is the same when using the stored energy to power the motor to accelerate the vehicle.
A DC-DC converter balances the voltage between the motor and the energy storage device, boosting or reducing the voltage as necessary. This reclaims more of the energy under braking and provides more under acceleration, making the vehicle more efficient.
“Our converter will be designed for use with 50 kW systems,” said Pete James, electronics specialist at Prodrive. “This means it can provide an additional power boost of up to 67bhp, which allows a hybrid car to use a much smaller petrol engine without any loss in performance. The other exciting prospect is that such a system could be used instead of a turbo or supercharger on higher performance sports cars.”
The project will require development of new technologies in the fields of power electronics and thermal management. One important feature of the system will be the prognostics and health monitoring, providing the converter with the ability to predict failure and shut down, or run in a reduced ‘limp home’ mode. Such functionality is a prerequisite in the automotive industry.
Vehicle packaging, price and efficiency are fundamental to the success of the DC-DC converter. The targets for the project are to produce a unit of efficiency of 96%, power/volume ratio of 6 kW/litre and power/weight ratio of 4 kW/kg.