Dynamic optimization of mechanical/electrical power flow in parallel hybrid electric vehicles

摘要

This paper deals with the optimization of the instantaneous mechanical/electrical power split in parallel hybrid electric vehicles. Traditionally, this perennial optimization question has been handled by various control strategies based on the instantaneous state of the system (vehicle, IC engine, EM machines, battery state-of-charge, transmission operating points), and is based on the premise that global optimality results from instantaneous optimality. However, in the context of Hybrid Electric Vehicles, the overall strategy is most often globally charge-sustaining. This overall integral constraint transforms the nature of the optimization problem by rendering it non-local in time. Global state-of-charge sustainment over substantial times does not imply instantaneous state-of-charge sustainment. The optimization problem is further compounded by the lack of knowledge of the long-term future energy requirements of the vehicle, and the distance to the horizon at which the SOC should be nominally maintained.