Modeling And Control Of Wet Desulfurization System For Large Coal-fired Power Plants

In recent years,our country has appeared the large-scale environment pollution question,which has brought the serious negative influence to the people's health and the living environment.As a large pollutant emitter,the environmental protection rectification of power generation industry is highly valued by the state.Due to the serious environmental pollution caused by sulfur dioxide in the flue gas of thermal power plants,and the low degree of automation and control precision of the desulfurization control link in power plants,it is necessary to optimize the desulfurization control link of power plants in order to control SO2 emissions.The establishment of accurate system model is an important prerequisite for optimizing the desulfurization control system.In this paper,the WFGD(wet flue gas desulfurization)system for large-scale coal-fired thermal power units is established,and the relevant identification model and control system are established.The main research work includes:1.System identification based on improved differential evolution algorithm.This paper introduces the improvement of differential evolution algorithm in the modeling and simulation of limestone-gypsum wet flue gas desulfurization system for the first time.In this paper,the 3-sigma criterion and Butterworth filter are used for the processing of desulfurization data,model by decision tree analysis on the selection of input variables,to select the optimal variable set as the input variables of wet flue gas desulfurization system,the slurry pH value as output variables of WFGD and export of SO2 concentration,to establish a multiple input double output transfer function matrix model.2.Design of feedforward-feedback compound control system.This paper introduces the structure,characteristics and types of the feed-forward control system,gives the design method and steps of the system,and emphatically describes the selection principle and design parameters of the feed-forward feedback composite control system.Based on the above identification model results,the Matlab/Simulink model of the corresponding feed-forward/feedback composite control system was established by taking the slurry pH value and outlet SO2 concentration as the research objects.3.PID parameter tuning based on MCP standard transfer function model.Based on capacity of inertia(MCP,multi-capacitive process)standard principle and main structure of the transfer function model,model related characteristics,and set up appropriate for the setting method of PID controller parameters in the model(MCP-PID),respectively,for single capacity inertial process,double let inertia process,single and double capacity delay time delay process P controller,PI controller and the PID controller parameter setting formula is derived.Finally,the applicability and accuracy of McP-pid tuning method were verified by taking slurry pH value and outlet SO2 concentration as research objects.By comparing the simulation results,the feed-forward feedback composite control system has the highest accuracy,the shortest stabilization time and the lowest overdose,which is suitable for the transfer function matrix model identified by the limestone-gypsum wet desulfurization system.Through modeling and simulation,this paper studies the identification and control of the limestone-gypsum wet desulfurization system of large coal-fired power generation units,and establishes the system model based on the improved differential evolution algorithm.Based on MCP standards are introduced in this paper,the transfer function model of the MCP-setting method of PID controller,get the very suitable for limestone/gypsum wet desulphurization system model and control method of multiple variables continuous system model identification provides a new train of thought,provides reference for the optimization of power plant desulphurization control link,for the practical operation of large coal-fired units provide theoretical support.