Design And Research Of Drum Water Level Control System For Circulating Fluidized Bed Boiler

Nowadays,under the background of the rapid development of science and technology,the research on process control field is also proceeding with a flourishing trend.Circulating fluidized bed boiler,a complex control system to complete corresponding controlling task,is also belonging to process control category.Boiler control contains many parameters that affect each other.Here,the content of this study is based on the water level in the water supply system,whi ch directly related to whether the other subsystems of the boiler can operate safely the required steam quality is ideal.In this study,the research object is a model of DHX25-1.25-All(25t/h rated evaporation and 1.25 Mpa rated pressure)circulating fluid ized bed boiler in the reconstruction of Yulong Copper Mine Plant.The control scheme and control algorithm of the boiler drum water level is mainly studied and the research work will be involved following three aspects:(1)The workflow of the water supply system is analyzed,especially for the internal and external disturbance factors and dynamic characteristics of the drum water level,which is combined with the advantages and disadvantages of the single impulse and double impulse control schemes.Finall y,the three impulse control scheme selected.In order to effectively eliminate the effects of “false water levels”,steam flow as a feedforward signal is introduced.(2)PID control has the advantage of high precision;however,its parameters are difficult to set.By combining the characteristics of fuzzy control theory without specific mathematical model,the corresponding drum water level control system is designed,which mainly uses fuzzy adaptive PID as the main regulator and constitutes the secondary regulator of PI control.Next,the corresponding model is built in MATLAB and simulated in the module environment of SIMULINK.Through making comparison of the simulation results,it is verified that the water level can be kept within a reasonable range whether the boiler workload becomes smaller or larger.(3)After communicating with the customer,the PLC hardware module is selected and the first and second instruments are matched.The redundant hardware control system is bridged to ensure the operation quality of the on-site boiler and the specific hardware design of the control system is competed.Through the lower configuration software STEP7 corresponding to PLC,the ladder diagram program related to water level control is compiled and the intelligent control algorithm is realized.Through the upper configuration software WinCC,the monitoring and operation interface is made,the communication connection between the upper computer and the PLC is realized,and the real-time acquisition of field data is completed.After debugging,the on-site water level control system is tested,and the final acceptance by customers is successful.