Study On Dual Closed Loop Decoupling Control Of Temperature And Humidity In VAV Air-conditioning System

Temperature and humidity have an important influence on people's living environment,and the control of temperature and humidity directly affects people's comfort.Air-conditioning temperature and humidity control system is a large-lag,time-varying,nonlinear and strongly coupled multi-variable system,there is a coupling between temperature and humidity.Under the summer working conditions,the humidity will decrease when the temperature in the room increases;the humidity will increase as the temperature decreases,so it is difficult to precisely control.Due to this mutual interference between loops,in order to allow the system to operate stably on the basis of the set value and improve system utilization,the coupling loop must be decoupled.Through the combination of theoretical analysis and experimental methods,based on the basic principle of dew point dehumidification,a decoupled double closed-loop control system with temperature and humidity was constructed.The mathematical models of fan pipe static pressure,chilled water pump supply water pressure difference,end valve opening-room supply air volume,room supply air volume-room temperature,chilled water valve opening supply air temperature,supply air temperature-room humidity control loop of Variable Air Volume System are established by using the least square method.On this basis,PID control is used for the fan-static pressure and chilled water pump-feedback pressure differential circuit,PI control is used for the end valve opening-room air supply loop,and Model free adaptive control(MFAC)is used for the chilled water valve-supply air temperature loop.Methods Underlying control,and then using cross decoupling,PID neural network decoupling control,simulation and experimental control of room temperature and humidity double closed loop decouplingcontrol system.Simulation results show that the bottom simulation control effect is better,and can quickly reach a stable state without overshoot.Because the PID neural network decoupling controller has a simple structure,it is easy to implement,The decoupler and the controller are integrated,which can not only solve the shortcomings of traditional decoupling methods with low accuracy.At the same time,it can realize online control.Under the summer working conditions,system simulations and experimental studies show that the PID neural network decoupling achieves stable time is twice faster than cross decoupling control on the basis of good decoupling control,and experimental studies have shown that the room temperature and humidity can make the system more energy-efficient while achieving the purpose of decoupling.