Energy management and control strategy design of a generation set in plug-in hybrid electric vehicles

This paper studies the optimal energy management approach and the control strategy of an engine/generator system, named "GENSET", for the purpose of extending the traveling mileage of a plug-in hybrid electric vehicle (PHEV). To derive the optimal energy management, two approaches are employed in this study. They are: (1) energy minimization control and (2)SOC-based control. For the first method, a theoretical-based analysis that searches the most efficient operation points exhaustively, called "Equivalent Consumption Minimization Strategy (ECMS)", is utilized. By giving BSFC/fuel consumption maps of the engine, as well as the efficiency contour of the generator, the optimal commands of torque and rotational speed of the GENSET can be calculated. Multi-dimensional tables are thereby constructed for the best power distribution between the GENSET and the energy storage system - A lithium battery package. The second method is a SOC-based control, which depends on two parameters: Expected charging time and current SOC status. The derived optimal results at different needed currents will be applied to the SOC-based control. These two energy management methods will be integrated into the operation modes of the control strategy for a vehicle control unit (VCU). The control software with a PHEV simulator is established on the Matlab/Simulink/Stateflow platform to verify the designed energy management and control strategy.