A unified thermal management framework for electric vehicles: Design and test bench implementation

An integrated thermal management system for the Heating, Ventilation, and Air Conditioning (HVAC) unit and the battery pack of an Electric Vehicle (EV) is proposed in this research. Unlike most of the existing work in the literature, in the current study, a unified thermal management framework is developed for the entire EV to address both the heating and cooling requirements for the battery pack and the HVAC system. Accordingly, a comprehensive and detailed 1D simulation model is first developed in which different parts of the vehicle, including the powertrain components, battery pack, cabin, compressor, battery chiller, expansion valves, pumps, radiator fan, etc., are accurately modeled and integrated into the EV general model in the GT-Suite environment. Subsequently, considering different heating/cooling scenarios in various environmental conditions (including air temperature, solar flux, metabolic rate, vehicle speed, etc.), effective control systems are designed for each subsystem, particularly the compressor, heaters, and pumps, using the gain-scheduling PI control method in the MATLAB/Simulink environment, coupled with the GT-Suite model. In particular, the control logic of the compressor balances the cooling effort between the battery and cabin evaporator based on a weighted temperature error. According to the simulation results, the proposed control system can appropriately fulfill the desired objectives, even in the case of pessimistic scenarios. Results showed that the controller maintained the battery temperature within the 27-37 degrees C range while reducing the cabin temperature from 70 degrees C to 29 degrees C within 10 min. The integrated system maintained safe battery temperatures under extreme ambient conditions of 50 degrees C. Then, the proposed framework is implemented on a complete test bench to evaluate the performance of the designed system in practice. Code generation enabled implementation on an automotive microcontroller. Finally, a preliminary test is conducted on an actual EV to evaluate its performance under real-world driving conditions. The obtained results indicate that the suggested thermal management system is capable of tuning the battery temperature as well as the cabin temperature in various conditions, complying with the protective rules required in real EVs.