蒸汽發(fā)生器水位控制畢業(yè)論文中英文資料外文翻譯文獻(xiàn)

1、 蒸汽發(fā)生器水位控制 中英文資料外文翻譯文獻(xiàn)research on fuzzy control for steam generator water leveli. introductionthe steam generator is one of the main devices in pwr nuclear power plant, in order to ensure the safety of nuclear power plant during operation; the steam generators water level must be controlled in a cer

2、tain range. when the nuclear power plant is running, as the steam flow or the water flow changing, the amount of boiling bubbles in the steam generator will change due to local pressure or temperature change, the instantaneous water level showed “false water level” phenomenon . the existence of “fal

3、se water level” made it difficult to control the water level. the introduction of feed-forward control to the traditional single-loop pid control can, in a certain extent, overcome the "false water level" phenomenon. but the conventional pid control method in the process of steam generator

4、 water level control has some shortcomings. to the steam generator that has highly complex, large time-delay and nonlinear time-varying characteristics, the pid parameters tuning is a tedious job and the control effect is very poor. furthermore, to achieve good control performance still as condition

5、s changing, it often needs to change the pid controller parameters. but the analog pid controller parameters are difficult to regulate online. fuzzy control is a kind of nonlinear control strategy based on fuzzy reasoning, which express operating experience of skilled manipulation men and common sen

6、se rules of inference through vague language. fuzzy control do not need to know precise mathematical model of controlled object, is not sensitive to the change of process parameters, is highly robust and can overcome non-linear factors, so, fuzzy control has faster response and smaller ultra- tone,

7、can get better control effect. based on understanding above, this paper design a steam generator water level fuzzy controller, the simulation shows that the controller has good control performance and practical value.ii. dynamic characteristics of steam generatorthe transfer function of pwr steam ge

8、nerators mathematical model of the general form shows below:y(s)=gw(s)qw(s)+gs(s)qs(s) （1）where y is the steam generator water level; qw for the water flow; qs for the steam flow; gw (s) for the impact of the water flow to the steam generator water level; gs (s) for the effect of the steam flow (loa

9、d) to the steam generator water level.the balance of the steam generator water level is maintained through the match between the water flow and steam flow. the process that water level changes with the steam flow or water flow changing can be regarded as a simple integration process, but impact of t

10、he water flow and steam flow s change on water level is different.a. dynamics characteristics under water flow disturbancesuppose steam flow gs remains unchanged, and water flow gw step increases, on the one hand because the temperature of feed water is much lower than the temperature of saturated w

11、ater in the steam generator, so that , when feed water entering, it will absorb a lot of extra heat, the vapor phase bubble contents will reduce, resulting in water level decreasing; on the other hand, the increase in water flow gw made it greater than steam load, and cause water level increases lin

12、early. comprehensive two factors, after the step increase of the water flow, the water level rise has a time delay process, showing a down then up.b. dynamic characteristics under steam load disturbancesuppose feed water flow gw remains unchanged, and steam load gs step increases, on the one hand th

13、e water level will flow down because the steam flow rate is greater than the water flow rate. on the other hand, as the steam load increased, vapor pressure is reduced; the bubble volume on the liquid surface increases, causing the water level increased. comprehensive two factors, after the step inc

14、rease of the steam flow rate, the water level down has a time delay process, showing a up then down. the impact on the water level of water flow or steam flow stepping decreased has similar principle as above.as analysis can be seen as above, when the water flow or steam load change, the water level

15、 did not follow the change immediately, but there is an opposite process at first. this phenomenon is called "false water level" phenomenon.iii. design of water level fuzzy controllerthe conventional pid controller has a poor control performance to the steam generator that exist “false wat

16、er level” characteristics, showing a greater overshoot in the tracking time. but a well-designed fuzzy controller is able to overcome the "false water level" phenomenon, and has good control performance. a. sstructure of fuzzy controllerthe structure showed in figure 1.fuzzycontrollerk1val

17、vegw(s)dx/dtk2gs(s)expected water leverstream flowwater leverwater floweec+-+-+figure 1. structure of steam generator water level fuzzy controllerchoose the water level error (e) and change rate of error (ec) as input of the fuzzy controller, the output of the fuzzy controller is the added value of

18、the valve opening signal u. meanwhile, use the steam flow feed-forward to overcome the "false water level" phenomenon, use water flow feedback to overcome fluctuations in water supply side . k1, k2 were water flow and steam flow transmitter conversion factor. to ensure the water flow to ma

19、tch the steam flow, k1 and k2 values should be equal to.b. fuzzy theory, fuzzy subset and membership functionthe fuzzy analects of e, ec and u are -6, 6, both with seven fuzzy sets nb (negative big), nm (negative middle), ns (negative small), zo (zero), ps (positive small), pm (positive middle) and

20、pb (positive big) to describe. e, ec and, u are all using triangular membership function (see figure 2).figure 2. input and output variable membership functionc. fuzzy control rule tablethe establishment principle of fuzzy control rules are: when the error is large, the output control volume should

21、give priority to eliminate error as soon as possible; when the error is small, the output control volume should givepriority to prevent overshoot. where ec is negative ,it shows that water level has a rising trend, if the water level is high at this time, then we should reduce the valve opening sign

22、al; whereas, we should open the valve more. through a comprehensive analysis of expertise, the establishment of rule table shown in table 1.table 1. fuzzy control rule table eecnbnmnszopspmpbnbnbnbnmnmnsnszonmnbnmnmnsnsnszonsnmnmnsnszopspszonmnsnszopspspmpsnsnszopspspmpmpmnsnszopspspmpmpbzopspspmpmp

23、bpbd. fuzzy reasoning and solutionthis fuzzy inference system uses mamdani. the basic properties of fuzzy inference system set to: "and" operation with a very small operation; "or" operation uses the maximum operation. using a very small operation fuzzy implication, fuzzy rules i

24、ntegrated with great operations center defuzzification method used. iv. simulation examplesa pressurized water reactor steam generator in chinese qinshan nuclear power station has empirical model g1 (s), g2 (s) below:where ps denote the rated load. when load at 15% 90% ps, use (6) and (8); when load

25、 less than 15% ps, use (7) and (8).figure 3. expected water level step response diagramthe coefficients in control system are k1=k2=0.5. water control valve is a king of linear valve, its gain is 4. the quantitative coefficients of e and ec are 6 and 60 respectively; the scale factor of u is 0.5. we

26、 limit water flow the range of 0 kg / s to the rated flow 258kg / s when simulation. consider the expected level step from the initial 0m to 10m, water level response is shown use the solid line in figure 3. for contrasting the increase effect of fuzzy controller, we also carried out using the tradi

27、tional pid control simulation. we can see, compared with traditional pid control, fuzzy controller has reported significant improvements in overshoot, settling time, steady degrees.v. conclusionthis paper designed a water level fuzzy control system aimed at steam generators characteristics of large

28、time delay and model uncertainty. we also gave a simulation to the steam generator of qinshan nuclear power plant, and achieved satisfactory results. the method can also be used for other large time -delay and time-varying process control model, and has broad application prospects.蒸汽發(fā)生器水位模糊控制研究1.導(dǎo)論蒸

29、汽發(fā)生器是壓水反應(yīng)堆式核電廠里的一個(gè)重要的設(shè)備。為了保證核電廠運(yùn)行的安全性，蒸汽發(fā)生器的水位必須控制在一定的范圍內(nèi)。核電廠的運(yùn)行中，因?yàn)檎羝髁亢徒o水流量的改變，蒸汽發(fā)生器里沸水中的氣泡數(shù)量會(huì)隨著局部氣壓和溫度的變化而改變，瞬時(shí)水位呈現(xiàn)“虛假液位”現(xiàn)象。正是由于“虛假液位”的存在使得水位控制變得困難。將前饋控制引入到傳統(tǒng)的單回路pid控制中，可以在一定程度上克服“虛假液位”的問題。但是蒸汽發(fā)生器的傳統(tǒng)pid控制仍然存在著一些不足。對(duì)于具有高度復(fù)雜，大滯后，非線性特征的蒸汽發(fā)生系統(tǒng)，不僅pid參數(shù)的調(diào)整單調(diào)乏味，控制效果也很差。并且當(dāng)條件改變時(shí)，為了獲得好的控制性能，通常需要改變pid控制器的參

30、數(shù)，但是模擬量的pid控制器參數(shù)的在線調(diào)整是很難的。模糊控制是一種基于模糊推理的非線性的控制方法，它體現(xiàn)了熟練操作人員的實(shí)際經(jīng)驗(yàn)和模糊語言推理的一般規(guī)則。模糊控制不需要知道被控對(duì)象的精確的數(shù)學(xué)模型，它對(duì)過程參數(shù)的變化并不敏感，魯棒性很強(qiáng)，能夠克服非線性因素，因此，模糊控制有更快的響應(yīng)速度，更小的超調(diào)，更好的控制效果?；谝陨狭私猓疚脑O(shè)計(jì)了一個(gè)蒸汽發(fā)生器水位的模糊控制器，仿真結(jié)果表明這個(gè)控制器有更好的控制效果和實(shí)用價(jià)值。2.蒸汽發(fā)生器的動(dòng)態(tài)特性壓水堆蒸汽發(fā)生器一般形式的數(shù)學(xué)模型的傳遞函數(shù)如下所示:y(s)=gw(s)qw(s)+gs(s)qs(s) （1）其中，y代表蒸汽發(fā)生器的水位；qw代表

31、給水流量；qs代表蒸汽流量；gw代表給水流量對(duì)蒸汽發(fā)生器水位的作用；gs代表蒸汽流量對(duì)蒸汽發(fā)生器的水位的作用。蒸汽發(fā)生器水位的平衡是靠蒸汽流量和給水流量的匹配來維持的。可以將水位隨蒸汽流量或者給水流量變化而變化看作一個(gè)簡(jiǎn)單的一體化過程，蒸汽流量變化和給水流量變化對(duì)水位的影響又是不同的。(1) 給水流量擾動(dòng)下的動(dòng)態(tài)特性假設(shè)蒸汽流量保持不變，而給水流量階躍增加，一方面，由于新增給水的溫度要比蒸汽發(fā)生器中的飽和水的溫度低很多，因此，當(dāng)新水進(jìn)入后就會(huì)吸收大量的額外熱量，水中的氣泡含量大大減少，從而導(dǎo)致水位下降；另一方面，給水流量大于蒸汽負(fù)荷，引起水位線性增加。綜合以上兩點(diǎn)，當(dāng)給水階躍增加，水位增長會(huì)有

32、一個(gè)延遲的過程，表現(xiàn)為先下降后上升。(2) 蒸汽負(fù)荷擾動(dòng)下的動(dòng)態(tài)特性假設(shè)給水流量保持不變，蒸汽負(fù)荷階躍增加，一方面，由于蒸汽流速比給水流速大，水位會(huì)下降；另一方面，隨著蒸汽負(fù)荷的增加，內(nèi)部蒸汽壓力降低，液面的氣泡容積增加，從而引起水位增加。綜合以上兩個(gè)因素，當(dāng)蒸汽流量階躍增加以后，水位下降會(huì)有一個(gè)延遲的過程，表現(xiàn)為先上升后下降。給水流量或者蒸汽流量階躍減少對(duì)水位的影響與上述有相似的原理。綜上所述，當(dāng)給水流量或者蒸汽負(fù)荷變化，水位不會(huì)立即跟隨變化，開始會(huì)出現(xiàn)一個(gè)相反的過程。這個(gè)現(xiàn)象就稱為“虛假液位”現(xiàn)象。3.水位模糊控制器的設(shè)計(jì)傳統(tǒng)pid控制器對(duì)于蒸汽發(fā)生器水位的控制效果不佳，存在“虛假液位”的現(xiàn)象，表現(xiàn)為跟蹤設(shè)定值時(shí)有較大的超調(diào)。但是，一個(gè)設(shè)計(jì)合理的模糊控制器能夠克服“虛假液位”的現(xiàn)象，有較好的控制效果。(1) 模糊控制器的結(jié)構(gòu)模糊控制器的結(jié)構(gòu)如圖1所示。fuzzycontrollerk1valvegw(s)dx/dtk2gs(s)expected water leverstream flowwater leverwater floweec+-+-+圖1 蒸汽發(fā)生器水位