Research On Modeling And Control Method Of Fresh Air Conditioning System

Fresh air conditioning can create a comfortable indoor environment and save energy,increasingly making it become the popular air conditioning equipment.Like other air conditioning systems,fresh air conditioning system is also a large hysteresis,nonlinear,strong coupling system.The key to realize the temperature and humidity control of fresh air conditioning is to establish a more accurate mathematical model and design an appropriate controller.This paper introduces the application background of fresh air conditioning system,and the research status of temperature and humidity control system modeling and control strategy.Based on the working principle of each link of air conditioning temperature and humidity control system,the mathematical model of fresh air conditioning temperature and humidity control system is established,and the traditional PID controller and fuzzy PID controller are designed.Finally,the fresh air conditioning temperature and humidity control system were simulated and dynamic response characteristic was analyzed.Firstly,this paper introduces the problems of energy consumption and indoor air quality in the field of air conditioning.Some solutions and technical difficulties to solve these problems was represented.And summarizes the research status of modeling and control algorithm in the field of air conditioning temperature and humidity control.Secondly,the structure and working principle of the temperature and humidity control system of fresh air conditioning are analyzed.Based on the law of conservation of mass and energy,the mathematical models of temperature control loop and humidity control loop are established for the control process of air conditioning compressor,refrigeration cycle,evaporator,PTC electric auxiliary heater,humidifier and heat and humidity balance of air conditioning room.Thirdly,on the basis of mathematical modeling,the structure of the temperature and humidity control system of fresh air conditioning is analyzed,and the transfer function of each link of the control system is derived.The parameters of the temperature and humidity control system of fresh air conditioning are identified by using the experimental data.The analysis shows that the results of parameter identification based on mathematical modeling have a high degree of fitting with the experimental data.Considering that the temperature and humidity control system of fresh air conditioning is a nonlinear and strong coupling system,the decoupling method of feed-forward compensation is discussed according to the coupling between temperature and humidity.Finally,in order to study the performance of different control strategies in the task of temperature and humidity control of fresh air conditioning,the traditional PID controller and fuzzy PID controller are designed,and the dynamic response characteristics of the two controllers under the conditions of model matching,model mismatch and strong interference are compared and analyzed.The results show that the fuzzy PID control strategy can shorten the rise time and adjustment time and restrain overshoot in quantity,the effect is better than the traditional PID control,and the fuzzy PID control algorithm shows strong robustness in the case of model mismatch and strong interference.