Trip-based SOC management for a plugin hybrid electric vehicle

Abstract

The control of PHEVs (Plug-in Hybrid Electric Vehicles) strictly depends on the management of the battery SOC (State of Charge) over a given trip. Indeed this key vehicle parameter affects the vehicle autonomy and its evolution may be enhanced by a proper match with further “external” variables, such as the availability of recharge stations and their characteristic speed for battery recharging.In this paper we propose an easily implementable control strategy, that is intrinsically robust with respect to the variation of used SOC over a trip and is based only on a preliminary knowledge of the target distance. Its use is experimentally demonstrated on a prototype PHEV to accomplish a defined target SOC at the end of the trip. A vehicle model has also been validated, in comparison with previously gathered experimental data, and then applied to analyze the control strategy behavior by varying input data such as trip distance, speed over time and target SOC. Results show that the target SOC may be obtained within an error in the range of 2%, allowing for a potential fuel economy increase up to 8.2% if compared with a baseline PHEV strategy. However fuel economy increase definitely depends on key trip characteristics such as speed profile, duration, distance, etc.