A thermal management system for the battery pack of a hybrid electric vehicle: modeling and control

Abstract

The lithium-ion battery pack in hybrid electric vehicles is an important energy storage device that requires proper thermal management. A considerable amount of heat is generated by the battery cells owing to their internal resistance during charging and discharging, especially for peak vehicle loads. This study focuses on developing a smart controlled thermal management solution in which a vapor compression system is integrated. A lumped-parameter cylindrical battery thermal model is developed with a Kalman observer to estimate the transient changes in the temperatures of the battery surface, the battery core, and the cooling air flowing around the cells. For the first time, the optimal cooling air temperature of the battery is investigated using optimal control theory. A model predictive controller is then introduced to regulate the refrigerant compressor and to track the ideal cooling air temperature. In a case study, the power consumption of the thermal management system and the behavior of the internal temperature of the battery are investigated under an urban assault cycle. For various operation configurations and conditions, the numerical results demonstrate that the peak error of the core temperature of the battery can be tracked within 0.25 °C of the target value and the energy consumption of the cooling system can be reduced by up to 58%.