蒸汽發(fā)生器水位控制畢業(yè)論文中英文資料外文翻譯

1、<p><b>　　中文2175字</b></p><p>　　Research on Fuzzy Control for Steam Generator Water Level</p><p>　　I. INTRODUCTION</p><p>　　The steam generator is one of the main dev

2、ices in PWR nuclear power plant, in order to ensure the safety of nuclear power plant during operation; the steam generator’s water level must be controlled in a certain range. When the nuclear power plant is running, as

3、 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” phenomeno

4、n . The existence </p><p>　　II. DYNAMIC CHARACTERISTICS OF STEAM GENERATOR</p><p>　　The transfer function of PWR steam generator’s mathematical model of the general form shows below:</p>

5、<p>　　y(s)=GW(s)QW(s)+GS(s)QS(s) （1）</p><p>　　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 generat

6、or water level; GS (s) for the effect of the steam flow (load) to the steam generator water level.</p><p>　　The balance of the steam generator water level is maintained through the match between the water fl

7、ow 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 the water flow and steam flow ‘s change on water level is

8、different.</p><p>　　A. Dynamics Characteristics under Water Flow Disturbance</p><p>　　Suppose steam flow GS remains unchanged, and water flow GW step increases, on the one hand because the tempe

9、rature of feed water is much lower than the temperature of saturated water 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, resu

10、lting 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 linearly. Comprehensive t</p><p>　　B. Dynamic Characteristic

11、s under Steam Load Disturbance</p><p>　　Suppose feed water flow GW remains unchanged, and steam load GS step increases, on the one hand the water level will flow down because the steam flow rate is greater t

12、han 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 t

13、he step increase of the steam flow rate, the water level down has a time delay process, showing a up then down. </p><p>　　The impact on the water level of water flow or steam flow stepping decreased has simi

14、lar principle as above.</p><p>　　As analysis can be seen as above, when the water flow or steam load change, the water level did not follow the change immediately, but there is an opposite process at first.

15、This phenomenon is called "false water level" phenomenon.</p><p>　　III. DESIGN OF WATER LEVEL FUZZY CONTROLLER</p><p>　　The conventional PID controller has a poor control performance t

16、o the steam generator that exist “false water level” characteristics, showing a greater overshoot in the tracking time. But a well-designed fuzzy controller is able to overcome the "false water level" phenomeno

17、n, and has good control performance. </p><p>　　A. Sstructure of Fuzzy Controller</p><p>　　The structure showed in Figure 1.</p><p>　　Figure 1. Structure of steam generator water lev

18、el fuzzy controller</p><p>　　Choose 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 the valve opening signal

19、 Δu. 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 tran

20、smitter conversion factor. To ensure the water flow to match the steam flow, k1 and k2 values should be equal to</p><p>　　B. Fuzzy theory, fuzzy subset and Membership Function</p><p>　　The fuzzy

21、 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 PB (positive big) to describe. e, ec

22、 and, Δu are all using triangular membership function (see Figure 2).</p><p>　　Figure 2. Input and output variable membership function</p><p>　　C. Fuzzy control rule table</p><p>　　

23、The establishment principle of fuzzy control rules are: when the error is large, the output control volume should give priority to eliminate error as soon as possible; when the error is small, the output control volume s

24、hould 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 signal; whereas, we should ope

25、n the valve more. Through a comprehensive analysis of expert</p><p>　　Table 1. Fuzzy control rule table </p><p>　　D. Fuzzy Reasoning and Solution</p><p>　　This fuzzy inference syste

26、m 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 implic

27、ation, fuzzy rules integrated with great operations center Defuzzification method used. </p><p>　　IV. SIMULATION EXAMPLES</p><p>　　A pressurized water reactor steam generator in Chinese Qinshan

28、nuclear power station has empirical model G1 (s), G2 (s) below:</p><p>　　where Ps denote the rated load. When load at 15% ~ 90% Ps, use (6) and (8); when load less than 15% Ps, use (7) and (8).</p>&l

29、t;p>　　Figure 3. Expected water level step response diagram</p><p>　　The coefficients in Control system are k1=k2=0.5. Water control valve is a king of linear valve, its gain is 4. The quantitative coeffic

30、ients of e and ec are 6 and 60 respectively; the scale factor of u is 0.5. We 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 10

31、m, water level response is shown use the solid line in Figure 3. For contrasting the increase effect of fuzzy controller, we also carried out us</p><p>　　V. CONCLUSION</p><p>　　This paper design

32、ed a water level fuzzy control system aimed at steam generator‘s characteristics of large time delay and model uncertainty. We also gave a simulation to the steam generator of Qinshan nuclear power plant, and achieved sa

33、tisfactory results. The method can also be used for other large time -delay and time-varying process control model, and has broad application prospects.</p><p>　　蒸汽發(fā)生器水位模糊控制研究</p><p><b>　　

34、1.導(dǎo)論</b></p><p>　　蒸汽發(fā)生器是壓水反應(yīng)堆式核電廠里的一個重要的設(shè)備。為了保證核電廠運行的安全性，蒸汽發(fā)生器的水位必須控制在一定的范圍內(nèi)。核電廠的運行中，因為蒸汽流量和給水流量的改變，蒸汽發(fā)生器里沸水中的氣泡數(shù)量會隨著局部氣壓和溫度的變化而改變，瞬時水位呈現(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

35、“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。并且當條件改變時，為了獲得好的控制性能，通常需要改變PID控制器的參數(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際經(jīng)驗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象的精確的數(shù)學(xué)模型，它對過

36、程參數(shù)的變化并不敏感，魯棒性很強，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?，本文設(shè)計了一個蒸汽發(fā)生器水位的模糊控制器，仿真結(jié)果表明這個控制器有</p><p>　　2.蒸汽發(fā)生器的動態(tài)特性</p><p>　　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:</p><p>　　y(s)=GW(s)QW(s)

37、+GS(s)QS(s) （1）</p><p>　　其中，y代表蒸汽發(fā)生器的水位；QW代表給水流量；QS代表蒸汽流量；GW代表給水流量對蒸汽發(fā)生器水位的作用；GS代表蒸汽流量對蒸汽發(fā)生器的水位的作用。</p><p>　　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?？梢詫⑺浑S蒸汽流量或者給水流量變化而變化看作一個簡單的一體化過程，蒸汽流量變化和給水流量變化對水位的

38、影響又是不同的。</p><p>　　給水流量擾動下的動態(tài)特性</p><p>　　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，當新水進入后就會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荷，引起水位線性增加。綜合以上兩點，當給水階躍增加，水位增長會有一個延遲的過程，表現(xiàn)為先下

39、降后上升。</p><p>　　蒸汽負荷擾動下的動態(tài)特性</p><p>　　假設(shè)給水流量保持不變，蒸汽負荷階躍增加，一方面，由于蒸汽流速比給水流速大，水位會下降；另一方面，隨著蒸汽負荷的增加，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。綜合以上兩個因素，當蒸汽流量階躍增加以后，水位下降會有一個延遲的過程，表現(xiàn)為先上升后下降。</p><p>　　給水流

40、量或者蒸汽流量階躍減少對水位的影響與上述有相似的原理。</p><p>　　綜上所述，當給水流量或者蒸汽負荷變化，水位不會立即跟隨變化，開始會出現(xiàn)一個相反的過程。這個現(xiàn)象就稱為“虛假液位”現(xiàn)象。</p><p>　　3.水位模糊控制器的設(shè)計</p><p>　　傳統(tǒng)PID控制器對于蒸汽發(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)定值時有較大的超調(diào)。

41、但是，一個設(shè)計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。</p><p><b>　　模糊控制器的結(jié)構(gòu)</b></p><p>　　模糊控制器的結(jié)構(gòu)如圖1所示。</p><p>　　圖1 蒸汽發(fā)生器水位模糊控制器的結(jié)構(gòu)</p><p>　　選擇水位偏差（e）和偏差變化率（ec）作為模糊控制器的輸入，

42、模糊控制器的輸出量為閥門開度的增量信號Δu。同時，以蒸汽流量作為前饋信號來克服“虛假液位”現(xiàn)象，以給水流量作為內(nèi)反饋信號來克服給水波動。k1，k2是給水流量和蒸汽流量的傳感器的轉(zhuǎn)換系數(shù)。為了保證給水流量等于蒸汽流量， k1和k2應(yīng)該相等。</p><p>　　(2)模糊理論、模糊子集和隸屬函數(shù)</p><p>　　e、ec 和 u 的模糊論域是[-6, 6]，用NB（負大）、NM（負中）、

43、NS（負小）、ZO（零）、PS（正?。M（正中）和PB（正大）7個模糊子集描述。e，ec 和Δu 都采用三角形隸屬函數(shù)（如圖2）。</p><p>　　圖2 輸入輸出隸屬函數(shù)</p><p><b>　　模糊控制規(guī)則列表</b></p><p>　　模糊控制規(guī)則建立的原則是：當偏差大，輸出控制量應(yīng)該優(yōu)先以盡快消除偏差為主；當偏差小，輸出控

44、制量應(yīng)優(yōu)先消除超調(diào)。當偏差變化率為負，這表明水位有上升的趨勢，如果此時水位高，應(yīng)減小閥門開度；相反，應(yīng)就應(yīng)當開大閥門。通過專業(yè)的分析，建立如表1所示的規(guī)則表。</p><p>　　表1 模糊控制規(guī)則表</p><p><b>　　模糊推理和模糊判決</b></p><p>　　本次設(shè)計的模糊推理系統(tǒng)采用Mamdani型。模糊推理系統(tǒng)的基本屬性

45、設(shè)置為：“與”算法為取小算法；“或”算法為取大算法。模糊蘊含采用取小算法；模糊綜合采用取大算法；清晰化采用重心法。</p><p><b>　　4.仿真實例</b></p><p>　　中國秦山核電站的一個壓水堆蒸汽發(fā)生器有如下的實驗?zāi)Ｐ停?lt;/p><p>　　其中，Ps表示額定的負荷。當負荷為15% ~ 90% Ps時，用公式(6) 和(8)

46、，當負荷小于15% Ps時，用公式(7)和(8)。</p><p>　　圖3 預(yù)期水位階躍響應(yīng)圖</p><p>　　控制系統(tǒng)的系數(shù)k1=k2=0.5。給水控制閥是一個線性閥，增益為4。e和ec的量化因子分別為6和60，u的比例因子為0.5。仿真時，我們限定給水流量的范圍在0kg/s到額定流量258kg/s。假設(shè)預(yù)期水位從0m上升到10m，水位響應(yīng)如圖3中的實線所示。為了比較模糊控制器增

47、加的效果，我們也作出傳統(tǒng)PID控制的仿真結(jié)果?？梢钥闯?，與傳統(tǒng)PID控制相比，模糊控制在超調(diào)量、調(diào)節(jié)時間和穩(wěn)態(tài)特性方面有重要的改善。</p><p><b>　　5.結(jié)論</b></p><p>　　本論文針對蒸汽產(chǎn)生器大延遲和模型不確定的特性，設(shè)計了一個水位模糊控制系統(tǒng)。我們還給出了秦山核電站的蒸汽發(fā)生器的仿真，并獲得了令人滿意的效果。這種方法同樣適用于其它的大滯后