An Efficiency Based Approach for the Energy Management in HEVs

A proper Energy Management Strategy (EMS) is a cornerstone for Hybrid Electric Vehicles consumption minimization. In general, to find the global optimal strategy, the knowledge of the entire mission profile of the vehicle is needed, making the real-time implementation impossible. A well-known solution to this problem is the Equivalent Consumption Minimization Strategy (ECMS) that optimizes at each time instant an equivalent fuel consumption, which combines the real fuel rate and a virtual fuel associated to the use of the battery energy. This virtual fuel is the actual battery power weighted by an equivalence factor, that implicitly accounts for the battery recharge efficiency during the vehicle mission. In this work, we propose an efficiency based EMS, rather than a fuel consumption based one. Despite the two approaches are proven to be identical under some assumptions, in the efficiency based solution the definition of the equivalence factor results easier. An offline estimation of this quantity is firstly proposed, eventually extended with a real-time adaptation. Simulation results show the effectiveness of the proposed approach, in particular when the adaptive strategy is used.