Energy management for plug-in hybrid electric vehicles based on road gradient

In consideration of the impact of road gradient on the vehicle driving demand,a predictive energy management strategy was proposed for plug-in hybrid electric vehicles(PHEVs) on the basis of road gradient provided by the vehicle navigation system.The knowledge of route data(trip distance,road gradient and altitude) was used to predict the electricity consumption. Then the state-of-charge(SOC) trajectory was planned for the charge depleting(CD) mode and the charge sustaining(CS) mode. With exact calculations of the charge timing,the SOC was charged to the target value before uphill and reached to the threshold after uphill in case of battery electricity shortage and over-discharge during uphill. The proposed adaptive SOC control strategy can improve the vehicle performance and is in favor of the full absorption of regenerative braking energy. Based on the MATLAB/Simulink platform,a simulation model was built for the plug-in hybrid electric system. The proposed energy management strategy based on road gradient prediction was verified to avoid battery over-discharge and to ensure sufficient electric energy during uphill.