Study On Optimal Control Strategy Of Circulating Fluidized Bed Boiler Combustion System

As a highly effective and clean coal combustion technique,CFB boiler has been widely used in commercial operations in my country.However,its current combustion automatic control system has a low operating utilization rate and the combustion state of the system generally deviates from the economic optimal state.And with the development trend that the proportion of new energy power generation into the grid increases year by year,the thermal power unit is forced to perform load peaking tasks more frequently,the performance of the CFB boiler combustion control system is required to continuously improve,so the research on the optimized control strategy of the CFB boiler combustion system is of great significance.CFB boiler combustion system is a complex control object with multiple variables,nonlinearity,large lag,and strong coupling characteristics.This paper aims to study the automatic control of CFB boiler combustion system.Fresh steam pressure and bed temperature are the key control parameters of the combustion system.Scientifically modeling and optimal control of fresh steam pressure and bed temperature are the key factors affecting the safe,environmentally friendly,efficient and economical operation of the CFB boiler.In order to achieve the above goals,this paper has done the following work:Firstly,based on the research of the existing CFB boiler combustion system control strategy,this paper adopts the combined method of analyzing the dynamic characteristics and using the historical data of the power plant to establish a dynamic mathematical model,which is used to express the dynamic response relationship of fresh steam pressure and bed temperature with changes in coal feed volume and primary air volume.It provides a theoretical basis for the decoupling strategy and the design of the main controller of the combustion circuit.Secondly,in view of the strong correlation and coupling between fresh steam pressure and bed temperature in CFB boilers,the feedforward compensation decoupling method is selected for decoupling after comparing various industrial decoupling control strategies.After decoupling,the CFB boiler combustion system is equivalently decomposed into two relatively independent control loops: coal feed rate to fresh steam pressure and primary air volume to bed temperature.And the effectiveness of the decoupling strategy is verified through simulation tests.Finally,in order to improve the performance of the boiler combustion control system,the main controller of the combustion control loop is optimized.On the basis of fully combining the advantages of conventional PID control and fuzzy control,a fuzzy adaptive PID controller based on dynamic universe is designed.The controller adjusts the scope of the fuzzy universe by introducing an expansion factor,So the fuzzy adaptive PID controller can more accurately set the PID parameters at different stages of the control process without changing the fuzzy tuning rules,and can achieve excellent CFB boiler combustion system operating conditions.Control performance.Target value tracking test,disturbance test and robust performance test prove that the fuzzy adaptive PID control based on dynamic universe has strong adaptability and robustness,and is suitable for actual thermal engineering site.