Simulation Modeling And Level Control Of Deaerator In Nuclear Power Plant

The deaerator is an important equipment in the power plant.Its main function is to remove the dissolved gas in the feed water and to receive the hydrophobicity of various systems to the deaerator.If the water level of the deaerator is too high,the deaerator head will be flooded,and the working fluid will be discharged from the overflow pipe,causing loss of working fluid and heat energy,and also cause unstable working pressure in the deaerator;if the water level is too low,it will reduce the inlet pressure of feed pumps,which is easily to cause cavitation of the feed pumps and even damage the feed pumps.Therefore,maintaining the water level of the deaerator normally while optimizing the quality of the water supply are of great significance to ensure the normal operation of the units.In this paper,the deaerator in the 1000MW Nuclear Power Plant was taken as the research object.Firstly,according to the working principle of the deaerator,its structural characteristics were analyzed.Under certain simplified conditions,the mathematical model of the deaerator was established according to the two laws of mass conservation and energy conservation,and the simulation model of the deaerator was established by developing component program on RINSIM platform.After the boundary parameters and initial values of the components were given for debugging,the steady state and transient operating conditions of the system verified the validity and accuracy of the model.Secondly,the water level control is complicated because the deaerator has hysteresis,instability and inaccuracy when the units load changes.In order to avoid the deaerator water level oscillation phenomenon,PID control was added.With referring to the deaerator water level control blueprint designed by the design institute,the logic control components were developed by the RINSIM platform to establish A Water Level Control System for the deaerator.The debug control results showed that the water level overshoot was reduced,the stabilization time was shortened,and the system stability was enhanced.However,when the deaerator water level had different degrees of disturbance or variable load operation,the PID controller could not adjust the water level more quickly and more accurately.This is because the traditional PID control is difficult to realize the parameter online self-tuning,and the water level adjustment will be delayed.and overshoot.Finally,a scheme of setting PID control parameters automatically by intelligent control method-BP Neural Network was put forward.It realized the neural network to adjust the PID control parameters online.The simulation results showed that the deaerator water level can automatically adjusted the optimal PID parameters in the transient state,and controlled the water level more quickly and accurately to ensure the safe and economic operation of the units.Compared with the traditional PID control,the control effects showed that the scheme can improve the water level control effect to a certain extent.In view of the wide application of deaerator,the simulation model of the deaerator and the research on water level control based on the model are universal,which provides reference value and guiding significance for power plants controlling.