Control-oriented Model of HVAC and Battery Cooling Systems in Electric Vehicles

Abstract

Energy-efficient thermal management of heating, ventilation, and air-conditioning (HVAC) and battery cooling systems is essential for an enhanced driving range of electric vehicles. With recent advances in vehicle connectivity technologies and vehicle computation units, a predictive model has been emphasized in control design. However, the system complexity due to refrigerant circuits and coupling with the battery cooling system makes it challenging to develop a computationally inexpensive model for potential model predictive control applications. This paper presents a novel control-oriented model to capture the behavior of a combined HVAC and battery cooling system for electric vehicles. To reduce the complexity due to the nonlinear two-phase flow heat transfer, the refrigerant circuit is modeled based on the assumption of a quasi-steady ideal vapor-compression cycle. The proposed model is calibrated with a three-step optimization process and then validated against a high-fidelity physics-based model with open-loop simulations. The simulation results show the effectiveness of the proposed model with four states and five actuators: the root mean square errors (RMSE) of the battery temperature and the coolant temperature are 0.41°C and 0.35°C, respectively, and the normalized RMSEs of the heat transfer rate at the heat exchangers are within the range of 2.8% to 10.6%.