Heating Control Strategy of CO2 Heat Pump Air Conditioning System of Electric Vehicle Based on Waste Heat Recovery Technology

Abstract

The control strategy of the thermal management system is crucial for ensuring the thermal comfort of an electric vehicles (EVs) cabin. However, the performance of heat pump air conditioning (HPAC) significantly deteriorates in low-temperature weather conditions. In recent years, the CO₂ HPAC system has emerged as a potential solution to address the insufficient heating capacity in such environments. In order to ensure cabin comfort and optimize winter mileage, a three-stage heating control method for CO₂ air source heat pump (ASHP) system is proposed in this article. Firstly, a simulation model is established and its feasibility is verified by comparing it with experimental results. Subsequently, the cabin's heating capacity is examined under four different low-temperature conditions (–5, −10, −15, and −20 °C). Optimal opening and closing strategies of each mode are discussed to maintaining the temperature requirements of the cabin. The three-stage heating control strategy demonstrates improvements in battery state of charge performance over 7200 s of running time compared to conventional CO₂ ASHP: optimization rates increase by 8.07% at −5 °C, a further increase by 10.03% at −10 °C, a substantial increase by 14.51% at −15 °C, and under extreme conditions of −20 °C, the optimization rate is as high as 16.21%.