Research On Drum Water Level Control And Its Realization On SMPT-1000 Device

In industrial production,boiler is one of the widely used equipment.Because of its special working condition of high temperature and high pressure,it is easy to cause safety accident when the water level of boiler drum is too high or too low.Therefore,in order to ensure the boiler running smoothly,it is required that the water level of the drum is stabilized within the normal range.The water level of drum has the characteristics of time delay,nonlinear and large disturbance,and the phenomenon of false water level is difficult to control.The traditional PID control of drum water level has three kinds: single impulse PID,double impulse PID and three impulse PID.Through the simulation research of three PID control modes on MATLAB/Simulink,the results show that the PID controller can easily produce false action on the feed water regulating valve when the false water level appears.As a result,the water level of the drum fluctuates intensely,and the control effect of the system is not ideal.In addition,because of the complex characteristics of the drum water level,it is difficult to obtain an accurate mathematical model of the drum.Therefore,by studying the model-free Adaptive control algorithm,and analyzing the stability of the model-free adaptive control algorithm,a model-free adaptive PID control scheme was designed and applied for the drum water level.MFAC controller is developed by Simulink platform to simulate the MFAC-PID control system of drum water level.Compared with the PID control effect,the results show that the model-free adaptive control algorithm is not dependent on the mathematical model and only needs the input and output data of the controlled system.The method can effectively reduce the false action on the regulating valve and the influence of disturbance on the system.To further improve the control performance of drum water level model-free control system,an improved model-free adaptive control algorithm with disturbance observer(Disturbance Observer Model-free Adaptive Control,DOMFAC)was applied to drum water level.The control scheme DOMFAC-PID has better ability to restrain and compensate the disturbance of drum waterlevel.The results of Simulink simulation show that the DOMFAC-PID control system of drum water level is stable and has short regulating time.It can overcome the influence of steam disturbance on the system when the false water level is appears,and the control effect is ideal.In order to verify the feasibility and practical control effect of model-free adaptive control algorithm,this paper takes boiler drum on SMPT-1000 device as control object and SIMATIC PCS7 as controller,through the configuration of hardware,software,network and the control algorithm programmed by CFC and SCL language,and the three-impulse PID and MFAC-PID control system of drum water level was built and run.The experimental results show that the model-free adaptive control algorithm has good robustness and is superior to the traditional PID control in interference suppression.