Study On The Control Scheme Of The Heat Network Supply Water Temperature In The Cooling System Of Power Plant

Under the background of saving energy and improving energy utilization rate,a thermal power plant in Shanxi uses the five-stage extraction steam of the steam turbine to heat the circulating water to drive the long-distance hot water type lithium bromide refrigeration unit,which realizes the recycling of the waste heat of the power plant and reduces the pollutant discharge of the airport refrigeration system.The temperature of the circulating water supply of the hot network is directly related to the working efficiency of the lithium bromide refrigeration unit.When the temperature of the circulating water supply of the hot network is too low and the heat source is insufficient,the overall refrigeration load is low.When the temperature of the circulating water supply of the hot network is too high,it will cause problems such as crystallization of the circulating solution,and the refrigeration unit will not work normally.At present,the temperature control of the circulating water supply of the hot network is manually controlled,and the labor intensity of the operating people is large,and the control effect is not good.This topic studies the control of the temperature of the circulating water supply of the heating network of a thermal power plant.Firstly,the process flow and main equipment of the power supply cooling system are introduced.According to the heat balance law,the dynamic process of the peak heater is established.Combined with the historical data collected on the site,the mathematical model of the steam inlet valve opening temperature-heat grid circulating water supply temperature in the case of the hot network circulating water flow of 360m3/h and 256m3/h is established respectively,and the model is confirmed.The single-loop PID control scheme of the circulating water supply temperature of the hot network is designed and simulated on the SIMULINK simulation platform.The result shows that the scheme has a long adjustment time and a large overshoot.Aiming at the problem of long temperature regulation and overshoot of the hot water circulation water supply in the single loop PID control scheme,the DMC predictive control scheme is designed.Firstly,the principle of DMC predictive control is introduced.The predictive control scheme of circulating water supply temperature of hot network is given,and the simulation research is carried out on SIMULINK platform.The simulation results show that under the given value step signal input and the spontaneous disturbance of the inlet valve adjustment degree,the predictive control scheme has less adjustment time and almost no overshoot,and the control effect is better than the single loop PID control scheme.Disturbance simulation result shows that the predictive control has good load adaptability.