A Powerflow Control Strategy to Minimize Energy Losses in Hybrid Electric Vehicles
Morten Hemmingsson
External reviewer: Anders Malmquist, Dep. of Electrical Machines and Drives, KTH

This work considers control of powerflow and energy storage in a Hybrid Electric Vehicle (HEV). The performance of a HEV, such as fuel consumption and emissions, depends  not only on the individual components but also on how the components are controlled. Control in this case is to determine  operating points for the components during driving, while control on the machine level, such as speed and torque control, is not an issue. A model of a series HEV has been developed. A number of different performance indices have been applied to the model and evaluated using methods from optimal control. These methods allow us to define simple specifications such as minimizing fuel consumption and to put constraints on emissions.
The resulting controller is impossible to implement since it is open loop and needs information about the future.
A controller that captures the behaviour of the optimal controller has been synthesised and tried on the model with satisfying result.

The developed controller has also been implemented on a full scale experimental platform, similar to the hybrid busses in Stockholm.
The experimental and theoretical results show good agreement. A reduction in fuel- consumption of about 10% seems possible when the results are compared with the busses in Stockholm.

Last updated 1999-02-04