Performance evaluation of steady-state and dynamic response for innovative configurations of EV cabin and battery coupled thermal management based on transcritical CO₂ cycle

Effective thermal management of the cabin-battery is crucial for operational safety of electric vehicles. To develop an optimal coupled thermal management system for cabin-battery that balances steady-state performance and dynamic response, four thermal management configurations (series configuration (SC), series-parallel configuration (SPC) with independent main/auxiliary heat exchanger (SPC_M/SPC_A) and parallel configuration (PC)) based on transcritical CO₂ cycles are proposed, alongside corresponding multi-objective coupled control strategies. Initially, the influence of ambient temperature, battery heat generation, and mass flow rate on steady-state performance metrics−COP, cooling capacity, power consumption, and battery temperature−has been comparatively analyzed. The SC exhibits the best steady-state performance, followed by the SPC_M and SPC_A, while the PC performs the worst. Furthermore, the SPC_M demonstrates an optimal CO₂ flow rate, and both SC and SPC_M cycles effectively maintain battery temperature below 45 °C with temperature differences on the battery pack surface under 1 °C. In contrast, SPC_A and PC fail to manage thermal control at high heat generation rates, resulting in temperature differences of up to 8.92 °C and 10.08 °C, respectively. Subsequently, the dynamic response time and maximum deviation characteristics of multi-objective controls are comprehensively evaluated, identifying SPC_A as the best performer, followed by SPC_M and SC cycles. Finally, dynamic anti-interference characteristics are rigorously tested using the Worldwide Harmonized Light Vehicles Test Cycle, where SC, SPC_A, and SPC_M cycles showcased superior resilience, maintaining maximum deviations in discharge pressure and cabin temperature within 0.05 MPa and 0.2 °C, respectively. Considering both steady-state and dynamic response performance, SPC_M is the ideal choice.