Hybrid electric vehicle (HEVs) represents a promising approach to reduce vehicle fuel consumption and exhaust emissions. However, due to the electric motor (EM) assistance, the engine load could be reduced and intermittent operation of engine is realizable in HEVs powertrain system. Consequently, the HEV powertrain heating-up process and engine fuel consumption will be changed accordingly.
Therefore, the influences of the EM power and battery capacity on the hybrid powertrain heating-up process and the engine fuel consumption will be analyzed, and 2 methods for optimizing the heating-up process by applying the auxiliary heaters (AHs) and the modification of the energy management strategy are represented.
The application of AHs can improve engine efficiency during heating-up; the controlling of the power flow from the AHs to the ICE cooling system is of special important. Accordingly, a thermal and energy management strategy (TEMS) is introduced in this paper to find a balance between fuel consumption and heating-up.
The TEMS is based on model predictive control (MPC) and dynamic programming (DP). MPC analyzes the forthcoming vehicle speed profile, calculates the power requirement and controls the AH accordingly. A cost function is then formulated based on the battery SOC and other driving conditions. DP solves the objective function and optimizes the power distribution between electric motor and engine.
The effects of the two methods are demonstrated by simulation in Matlab/Simulink. Simulation results are compared to demonstrate the optimized heating-up process.