Achieving greater efficiency, better packaging and improved cost-effectiveness from hybrid powertrain systems is a challenge facing the motor industry. Now, a new collaborative program has been launched in the U.K. to develop a dc-dc converter aimed at being more efficient, smaller, and more economical than others on the market. The converter would also enable regenerative braking to become more effective.
Led by Prodrive and partially funded by the U.K.’s Technology Strategy Board, the project is supported by HILTech Developments, International Transformers, LDV, Sloan Electronics, the University of Manchester, and Newcastle University.
Hybrid-vehicle systems without dc-dc converters typically incorporate an energy storage device such as an ultracapacitor or battery as well as an electric motor, explained Prodrive electronic specialist Pete James. “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.”
In contrast, James said that 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.”
James said the consortium’s converter would be designed for use with 50-kW (67-hp) systems. This would mean that it could provide an additional power boost of up to 50 kW (67 hp), facilitating the use of a downsized power unit in a hybrid car without any performance loss. “The other exciting prospect is that such a system could be used instead of a turbo or supercharger on higher-performance sports cars,” he added.
The project will require development of new technologies in the fields of power electronics and thermal management. James emphasized the importance of prognostics and monitoring of system health, which help the converter to predict failure and shut down, or run in a reduced “limp-home” mode.
Targets for the project are to produce a converter with 96% efficiency, a power/volume ratio of 6 kW/L (8 hp/L), and a power/mass ratio of 4 kW/kg (2.4 hp/lb).