Modeling And Control Of Power Plant Coal Mill Based On System Dynamics

The "rich coal,poor oil,less gas" energy characteristics determine that coal-fired power generation is long-term main power energy in China.With the continuous increase of installed capacity of thermal power stations in China,medium speed coal mill direct-fired pulverizing system is used more widely.As the main equipment of the direct-fired pulverizing system,medium speed coal mill,whose safety and economic performance directly affects the safety and economy of the boiler operation.Therefore,it is necessary and practical to study the modeling and control of medium speed coal mill.From the perspective of mass and energy balance,based on the principles of system dynamics,the causal loop diagram that can reflect causality of the system internal variables and stock and flow diagram that can reflect quantitative mathematical relationships of the system internal variables are established according to working principle of medium speed coal mill.Then,the simulation experiment of the established model was carried out in the system dynamics software Anylogic.According to comparison of the system dynamic and differential equation model simulation results,the validity and correctness of the established system dynamic model is proved.Using the established system dynamic model,the classical PID controller is selected to control the medium speed coal mill with the control scheme that is outlet temperature adjusted by cold primary air valve and primary air flow adjusted by heat primary air valve.The parameters of the controller are tuned by the engineering setting method and realizing the control of outlet temperature and primary air flow.The fruit fly optimization algorithm(FOA)which is used widely in the areas of system parameter identification and optimization and has the characteristics of small computation,simple principle and good convergence,is used to optimize the controller parameters to overcome adjust time too long,large overshoot problems.The control effect of before and after optimization controller was compared and analyzed,and the results show that the controller after optimization has a better control effect.Given the large inertia and delay characteristics of coal mill,combined with the fuzzy control theory,self-tuning fuzzy PID controller is designed based on after optimization controller.The control effect of after optimization controller and self-tuning fuzzy PID controller is compared and analyzed,and the results show that the self-tuning fuzzy PID controller has a better control effect.