Abstract: To solve the problems of reduced energy efficiency and “defrosting without frost” caused by the traditional timed defrosting strategy in air conditioners, a synergistic control strategy based on precise frost point judgment and active frost suppression with variable frequency is proposed. This strategy establishes a mapping of ambient temperature-humidity to frosting status, using the frost point temperature as the core criterion to accurately determine the timing for defrosting. Concurrently, it actively raises the evaporation temperature by dynamically adjusting the compressor frequency during different stages of frost development to suppress frost nucleation and retard frost layer growth. Experimental results show that this synergistic strategy can effectively extend the continuous heating period by 36% under the -7℃/RH70% condition, and significantly improve the comprehensive winter energy efficiency by 6.7% under the -12℃/RH65% condition. This research provides an effective technical solution for enhancing the heating comfort and energy-saving performance of heat pump air conditioners in cold and humid environments.

Key words: Heat pump air conditioner, Frost suppression control, Frost point temperature