Controlling an electric turbo compound system for exhaust gas energy recovery in a diesel engine

This paper describes control system developments for an electric turbocompound system on heavy-duty diesel engines. The system consists of a turbocharger with an electric generator integrated into the turbocharger shaft, and an electric motor integrated into the engine crankshaft. The generator extracts surplus power at the exhaust air turbine, and the electricity it produces is used to run the motor mounted on the engine crankshaft, recovering otherwise wasted energy in exhaust gases. The ultimate goal of this system is to improve the overall fuel efficiency of the engine. The electric turbocompound system provides added control flexibility because it is capable of varying the amount of power extracted from exhaust gases. This allows for control of engine boost, and thus air/fuel ratio. The system configuration, turbocharger features, and the development of a system control strategy are presented