| With the continuous development of science and the continuous improvement of living standards,people have higher and higher requirements for the thermal comfort and air quality in buildings,which makes the role of air conditioning more and more important in daily life and production.The traditional constant air volume air conditioning system takes the maximum cold,heat and wet load of the room as the design load.In most cases,it works for partial load,and the energy consumption is large,which is difficult to meet the needs of modern energy saving and emission reduction.The variable air volume(VAV)air conditioning system has gradually become the mainstream of central and international air conditioning systems at home and abroad due to its low energy consumption,flexible control and diversity.The external air parameters,the personnel activities in the air-conditioning system room,and the heat dissipation of the electrical appliances vary greatly.The air conditioning process and the operating characteristics of the air conditioner actuators are highly nonlinear.There is strong coupling between control loops and complete decoupling is difficult.As time goes by,the device will age and change,resulting in system parameter changes,etc.The above reasons make the temperature control of VAV air conditioning system nonlinear,large time lag,uncertainty and difficult to establish accurate mathematical models.These characteristics bring a big problem to the design of the VAV air conditioning temperature controller.Therefore,improving and designing the temperature controller of the VAV air conditioning system has important research value and practical significance.The ADRC algorithm is a new type of control algorithm that does not depend on the controlled object model.It has strong anti-interference ability,fast response,high control precision,simple algorithm and easy digital implementation.It uses the "observation + compensation" method to deal with the nonlinearity and uncertainty in the control system,and with the nonlinear feedback method,it can effectively improve the dynamic performance of the controller.According to its unique characteristics,ADRC can observe and compensate the thermal disturbance in real time,which can effectively overcome the uncertainty and thermal disturbance in the temperature system of VAV air conditioning system and realize the decoupling between the control loops.This algorithm solves the problem of temperature control in VAV air conditioning system.Firstly,this paper analyzes the working principle of VAV air conditioning temperature control system,the commonly used control loop and coupling relationship.It was determined that the VAV air conditioning temperature control system was modified by ADRC technology.Secondly,according to the characteristics of each controlled object in the VAV air-conditioning wind system,LabVIEW and MATLAB software are used to establish the mathematical model based on the theory of least squares.In order to improve the control effect,a cascade active disturbance rejection controller is designed by introducing the active disturbance rejection control into the cascade-controlled temperature loop with taken the opening of the air valve of variable air volume terminal device as the intermediate adjustable quantity.The cascade ADRC controller is designed to achieve precise control of the room temperature of the air conditioning system.There is strong dynamic coupling between the room temperature loop,the supply air temperature loop and the air duct static pressure loop in the VAV air conditioning system,and it is used as the total disturbance in each loop.The ADRC decoupling controller guarantees the stable operation of the system and improves the control effect.Finally,the simulation and experimental verification of the above control scheme show that the above control scheme has a good application effect in the actual operation of the VAV air conditioning temperature control system,and improves the quality of the temperature control of the VAV air conditioning system. |
