| Through the increasingly fierce contradiction between environmental protection and industrial development,countries around the world pay more and more attention to the strict control of low-carbon emissions,and also pay more and more attention to the construction and application of low-carbon new energy.As a new low-carbon energy with great development potential,nuclear power plays an important role in the transformation of low-carbon emission reduction and green development in china.Steam Generator is the very important equipment between first poop and second loop in nuclear power plant.The level control of Steam Generator makes a big sense on the safety and economic of the nuclear power plant.Therefore,it is very important to have a good design on level control of Steam Generator,and it is valuable to have the research on level control of Steam Generator.Generally,Based on the simplified power-related generator level simulation model,the traditional multivariable compound serial PID controller has been designed for level control of SG in the nuclear power plant in our country.This kind of PID control has advantages of simple-structure,Response in time,precision control etc.But because of the nonlinearity,time varying,time lag and non-minimal phase for Steam Generator level control,it still can not work well in some cases.It needs a lot of additional operation by the operator which make the increase of the workload and even the risk of economic and safety problems caused by human-factor mistake.So there is much more requirement and challenge for the design of SG level control.It is necessary to make optimization analysis on the related control system in order to improve the control effect of SG level control system under various transient conditions in the process of full load scope(especially under low load).This paper studies and analyzes the structure and functional principle of the steam generator of the second generation PWR nuclear power plant,its dynamic characteristics and water level transient characteristics,deduces and analyzes the function of water level and related parts,and on the basis of the above mathematical model,combined with the functional requirements of the actual project,accomplish the typical water level control system design and parameters adjustment.Meanwhile after analysing the existing problems according to the work experience and site investigation,three improvement measures of the generator water level control are proposed:1)By analyzing and fitting the historical data,a new load-level setting curve is proposed to improve the water level regulation performance in the stage of power increase and power decrease.2)Through the design of nozzle valve flowmeter,the measurement accuracy of steam flow,level setting and pump speed setting value under low load is improved.3)Based on the combination of fuzzy control technology and traditional PID technology,a fuzzy self-tuning PID water level controller for PWR is designed,which can effectively improve the control performance.The above optimization measures make the control scheme not only have the characteristics of convenient realization,small static difference and high reliability of traditional PID scheme,but also have better adaptability to the characteristics of non-linear,time-varying,strong lag and non minimum phase of generator water level system,so that the new design can obtain better regulation effect to improve the automation level,economic level and safety level of power plant control. |
