Research On Control Strategy Of Variable Air Volume Air Conditioning System Based On Fuzzy Control And Ventilation Network

Since its advent in the mid-1960s,the variable air volume air conditioning system has been tried and popularized in developed countries and regions such as the United States,Europe,and Japan due to its energy saving,comfort,and flexibility,and its utilization rate in high-rise buildings in the United States Up to 90%.However,the application effect of variable air volume air conditioning system and its control technology in China is not ideal.Due to the complicated structure and control method of variable air volume air conditioners,the faults are concealed during operation.At present,the domestic fault diagnosis for existing systems is mainly focused on hardware fault diagnosis,and there are few studies on faults caused by control logic design problems and improper personnel operation.At the same time,there are different degrees of coupling relationship between the parameters of the variable air volume air conditioning system,which is easy to cause the system hydraulic imbalance and fail to achieve the expected control effect.This article first introduces the hardware composition,system structure and control method of the variable air volume air conditioning system.From the perspective of the system structure and working principle,it summarizes various hardware and software failures that may occur during the operation of the variable air volume air conditioning system;The type of connection explains the parameter performance under various types of faults;it forms the fault diagnosis method of VAV air-conditioning system based on "hardware fault diagnosis-control logic diagnosis-human operation diagnosis".Then,explore the factors that affect the control effect of the variable air volume air conditioning system.Starting from the three aspects of system hydraulic characteristics,control parameters,and control methods,Trnsys,Matlab,and Flowmaster simulation software are used to establish a variable air volume air conditioning system model to quantitatively analyze the impact of various factors on flow distribution and temperature control.The investigation found that the impact of each end is mainly from the valve adjustment of the other end of the road,the degree of impact is about 18.75%,and the influence from the other branch ends is only about0.82%.In terms of control parameters,the selection of PID parameters has a significant impact on the stability and rapidity of the system.The increase of the control period can enhance the stability of the system,but the rapidity decreases.In terms of control methods,subject to its own design constraints,the static pressure method and the total air volume method have failed to control the conditions with large load fluctuations.The variable static pressure method can better adapt to changes in various working conditions,but its control method based on the frequency conversion of the terminal valve position makes the system fluctuate greatly.The three methods of constant static pressure,variable static pressure,and total air volume account for 35.51%,75.45%,and 43.21% of the temperature controllable durations that are inconsistent with the design load.Based on the research on the influencing factors of the control effect of variable air volume air conditioning system,a new control method based on fuzzy control and ventilation network is proposed.The control structure of the variable air volume air conditioning system is adjusted,on this basis,the ventilation network calculation system pipe network flow distribution is adopted,and fuzzy control is introduced to calculate the terminal demand air volume.The control effect of variable static air pressure control method,variable static pressure control method,total air volume method and ventilation network method on variable air volume air conditioning system was compared by using simulation software of variable air volume air conditioning system simulation experiment platform.The evaluation indicators include the proportion of temperature controllable duration and system energy consumption.Experiments show that under the design load condition,the new control method proposed in this paper accounts for 100% of the temperature controllable time,which is 18.23% and 11.42% less energy than the static pressure method and the total air volume method.Under load fluctuation conditions,the temperature controllable duration accounted for 93.33%,which was better than 75.45% of the variable static pressure method,and the energy consumption levels of the two were similar..