Research And Application Of NO_x Reduction Control System Based On Fuzzy Self-tuning PID

In recent years,there are different degrees of fog and haze in most parts of China,and the emission of the chimneys in the thermal power plant is one of the main causes of this phenomenon.As a result of the country further restricts the NO_x content of thermal power plants,so how to effectively reduce the content of NO_x in the flue gas is an urgent problem.At present,the SCR denitrification system of power plant is controlled by normal PID,and can be effectively controlled in the condition of steady state or small change.When the load is heavily wavy,little or large ammonia will be sprayed as untimely control.So the NO_x value of export will cause strong variations.The dissertation takes the load variation in thermal power plants as background,a fuzzy inference based denitration control system is proposed.This method has fast response and strong applicability,and can control better when load changes.Compared with the normal PID,fuzzy control language is simple and can combine with expert specialistic experience to achieve the anticipated effect.It is an intelligent control method and can be applied to large delay,nonlinear and time-varying systems.Because the fuzzy control is a nonlinear control and can not eliminate the static difference,so it is not used in practical application.In this paper,the control strategy combines the fuzzy control and PID control.The fuzzy self-tuning PID control ensure the rule of parameters according to PID adjustment experience,and adjusts the parameters when error occurs.The quantification factor and scale factor of normal fuzzy self-tuning PID control is fixed,because the load changes frequently in thermal power plants so that there may be a untimely control.A fuzzy self-tuning PID control strategy based on extension factor is proposed,it can enhance the robustness of the control system.The step response curves,anti disturbance curves,tracking ability curves and curves of load variation of different control strategies under load conditions of 58%,75%,92% is analyzed with MATLAB,the experimental results show that the fuzzy self-tuning PID control with extension factor is superior to the traditional fuzzy self-tuning PID control and PID control in real-time and robustness.