Control And Simulation And Modeling Of The VAV Air-Conditioning System

Along with the progress of modern civilized society, improvement of people’sliving standards and development of science and technology, people living environmentdemands increase, air conditioning has become an indispensable part of people’s lives.In production and life, air conditioning technology bring convenience and comfort topeople. At the same time, people also begin to explore problem solving methods, suchas efficient operation of air conditioning, high degree automation and control, energysavings, etc. There are some defects in control function of traditional constant airvolume air conditioning system, it is difficult to meet modern needs. Variable AirVolume air-conditioning become mainstream of central air conditioning systemdevelopment and research by virtue of its flexibility and energy efficiency. Currently, itis the most promising air conditioning system.Relative to constant air volume system, variable air volume system adjusts indoortemperature and humidity of air conditioning system by air volume change or supply airtemperature regulation. Air flow is adjusted by VAV terminal devices, and air flow of airhandling units (AHU) is adjusted, supply air temperature is adjusted automatically,meanwhile blower speed is adjusted automatically, fan power is reduced, energy issaved, it also meets the requirements of indoor comfort.Various aspects of typical characteristics of air conditioning system is analyzed inpaper, and cooler, heater, room and other mathematical models of VAV system arederived and established. Performance predictive of control system can be implementedthrough computer simulation, Dynamic characteristics were obtained in order to assessthe performance of the real system, dynamic characteristics are obtained in order toassess the performance of the real system, resulting in an effective control program.Based on mathematical model of each VAV systems typical links, correspondingsimulation model is built. And model control process at room temperature variation issimulated. Appropriate input signal is added to observe model response. Applicability ofthe model has been validated. Because of model universal, depth study of VAV system control strategies have been laid.Energy efficiency of VAV system is good, it can meet the requirements of roomtemperature comfort. But during the operation, we need appropriate control meansto ensure the stability of system operation and superior energy efficiency. TraditionalPID control can not tune parameters online, and it has low control accuracy, poorstability, air conditioning control requirements can not be met. The fuzzy PID controlcombines the advantages of fuzzy theory and traditional PID control, there optimizedparameters are sent to PID controller, parameter self-tuning is completed, satisfactorycontrol effect is obtained. Fuzzy PID control parameters is self-adaptive with changes inenvironment, while control requirements is reached, it is accuracy and efficiency.In this paper, VAV air-conditioning temperature control system is used as researchobject and explored theoretically. Temperature control has large inertia, delay andnon-linear characteristics. For this feature, cascade control of fuzzy PID algorithm isused in the main loop, system is adjusted online during operation. Room temperaturecontrol relevant mathematical model of VAV air-conditioning system is established inpaper, room temperature control system is designed, temperature control in simulinkenvironment is researched. Temperature changes under PID cascade control andtemperature changes under string level self-tuning fuzzy PID control are simulatedrespectively. Compared with simulation results conclusion is drawn: In this paper,compared with the former one, self-tuning fuzzy PID cascade control has significantadvantages both in terms of control accuracy, interference and other aspects. Significantadvantage of control method is verified in comparison with other commonly usedcontrol methods. Models and control strategies are achieved good control effect, systemrequirements for energy efficiency and comfort are satisfied. It has a certain referencevalue for the improvement of VAV air-conditioning system energy saving technologyand the development of intelligent control technology.