Study And Application Of The Fuzzy Self-Tuning PID Control In Superheated Steam Temperature System

In recent years, with the rapid development of our country electric powerindustry, the unit capacity of power plant is gradually enlarged, the requirementsof the thermotechnical automation improve continuously. Among them, thesuperheated steam temperature of the boiler as an important index measurequality of superheated steam, in relation to the safety and economic of the powerplant operation. A superheated steam temperature is too high to security working,and when steam temperature too low will influence the economic benefit ofpower plant. So, superheated steam temperature of the boiler must be strictlycontrolled as one of the important indexes.At present, the conventional PID control method is widespread used tocontrol a superheated steam temperature of power plants. Because a superheatedsteam temperature as a control object which has big inertia and large delay, and ithas the nonlinear and time-varying characteristics, so the conventional PIDcontrol difficultly achieve a excellent control level. To solve the control problem,it is necessary to use a advanced control method. This paper mainly include：1. The characteristics of the superheated steam temperature are detailedintroduction. All kinds of influencing factors of the steam temperature isdiscussed.The paper analyzes the static characteristics of the superheated steamtemperature. Finally, the paper emphaticanalyzes the dynamic characteristic ofthe superheated steam temperature in the disturbances of steam flow, thedisturbance of smoke and the disturbance of desuperheating water.2. Theory basis and design method of the fuzzy self-tuning PID control arestudied. First, this paper introduces the basic theory and the developmentalhistory of the fuzzy control, and the detailed explain the characteristics and thebasic control principle of the fuzzy control. Second, it analyzes the advantagesand disadvantages of conventional PID control and fuzzy control, and putforward the combination of traditional PID control method and the fuzzy control technology to overcome the shortage of each other. And the thought of fuzzy self-tuning PID control is introduced in this paper. Finally, through the combinationof the fuzzy control and PID control, it designs a kind of fuzzy self-tuning PIDcontrol method, can realize the on-lineautoregulation of PID parameters.3. The paper study to how to apply fuzzy self-tuning PID control in asuperheated steam temperature control system. First, we introduces several thetypical plans of superheated steam temperature control, and focuses onintroducing the cascade control system of steam temperature which is appliedwidely in current. Secondly, the fuzzy self-tuning PID controller is applied to thesuperheated steam temperature control system of boiler, and it use theSIMULUNK modules of MATLAB software to contrast the simulation of thiscontrol mode and the conventional PID control mode. Through the simulationresults show that: the fuzzy self-tuning PID controller has better performancethan the conventional PID controller, which have the characteristics of shortersetting time, less overshoots, shorter steady time, higher accuracy and betteradaptability. Finally, the practical application of the fuzzy self-tuning PIDcontroller in a superheated steam temperature control system is further discussed.4. This paper using particle swarm algorithm optimize to the parameters offuzzy self-tuning PID control system. The principles and characteristics ofparticle swarm optimization algorithm are introduced. Then, using this particleswarm algorithm optimized the parameters of fuzzy self-tuning PID control.Finally, MATLAB is used to simulate the system which is optimized, and thesimulation results indicate that the ability of system in stability, quickness,disturbance, tracking performance and inhibit delay all has improved greatly.