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1、<p><b> 中文譯文</b></p><p><b> 1 變頻技術(shù)</b></p><p> 1.1 變頻技術(shù)的普及前景</p><p> 電機(jī)交流變頻調(diào)速技術(shù)是當(dāng)今節(jié)電、改善工藝流程以提高產(chǎn)品質(zhì)量和改善環(huán)境、推動(dòng)技術(shù)進(jìn)步的一種主要手段。變頻調(diào)速以其優(yōu)異的調(diào)速和起制動(dòng)性能,高效率、高功率因數(shù)和節(jié)電
2、效果,廣泛的適用范圍及其它許多優(yōu)點(diǎn)而被國(guó)內(nèi)外公認(rèn)為最有發(fā)展前途的調(diào)速方式。電氣傳動(dòng)控制系統(tǒng)通常由電動(dòng)機(jī)、控制裝置和信息裝置3部分組成,電氣傳動(dòng)關(guān)系到合理地使用電動(dòng)機(jī)以節(jié)約電能和控制機(jī)械的運(yùn)轉(zhuǎn)狀態(tài),實(shí)現(xiàn)電能-機(jī)械能的轉(zhuǎn)換,達(dá)到優(yōu)質(zhì)、高產(chǎn)、低耗目的。電氣傳動(dòng)分成不調(diào)速和調(diào)速兩大類,調(diào)速又分交流調(diào)速和直流調(diào)速兩種方式。不調(diào)速電動(dòng)機(jī)直接由電網(wǎng)供電,但隨著電力電子技術(shù)的發(fā)展這類原本不調(diào)速的機(jī)械越來(lái)越多地改用調(diào)速傳動(dòng)以節(jié)約電能(節(jié)約15%~20%或
3、更多),改善產(chǎn)品質(zhì)量,提高產(chǎn)量。在我國(guó)60%的發(fā)電量是通過(guò)電動(dòng)機(jī)消耗的,因此調(diào)速傳動(dòng)是一個(gè)重要行業(yè),已經(jīng)得到國(guó)家重視,目前已有一定規(guī)模。</p><p> 近年來(lái)交流調(diào)速中最活躍、發(fā)展最快的就是變頻調(diào)速技術(shù),變頻調(diào)速是交流調(diào)速的基礎(chǔ)和主干內(nèi)容。上個(gè)世紀(jì)變壓器的出現(xiàn)使改變電壓變得很容易,從而造就了一個(gè)龐大的電力行業(yè)。長(zhǎng)期以來(lái),交流電的頻率一直是固定的,變頻調(diào)速技術(shù)的出現(xiàn)使頻率變?yōu)榭梢猿浞掷玫馁Y源。</p&
4、gt;<p> 這10年來(lái),變頻技術(shù)的應(yīng)用在我國(guó)有很大的發(fā)展,并取得了良好的效果可以說(shuō),變頻技術(shù)已為大多數(shù)用戶所接受,但是不能不指出,我國(guó)在變頻技術(shù)的應(yīng)用方面,與發(fā)達(dá)國(guó)家的水平尚有很大差距,目前,我國(guó)在用的交流電動(dòng)機(jī)使用變頻調(diào)速運(yùn)行的僅6%左右,而下業(yè)發(fā)達(dá)國(guó)家已達(dá)(60%~70%),日本在風(fēng)機(jī)、水泵上變頻調(diào)速的采用率已達(dá)10% ,而我國(guó)還不足0.01%.在日本,空調(diào)器的70%采用了變頻調(diào)速,而我國(guó)才剛剛起步。從這個(gè)現(xiàn)實(shí)出
5、發(fā),變頻技術(shù)尚有很大的發(fā)展空間,應(yīng)該鍥而不舍地做好推廣應(yīng)用工作。</p><p> 而且隨著控制技術(shù)和控制手段的不斷提高,變頻調(diào)速又由變壓變頻控制的變頻調(diào)速發(fā)展到了矢量控制變頻調(diào)速,通過(guò)控制交流電動(dòng)機(jī)里相當(dāng)于并勵(lì)直流電動(dòng)機(jī)勵(lì)磁繞組的磁通變化,提高變頻器的恒轉(zhuǎn)矩輸出范圍和動(dòng)靜態(tài)特性,使得交流電動(dòng)機(jī)變頻調(diào)速系統(tǒng)的性能超過(guò)了直流電動(dòng)機(jī)調(diào)壓調(diào)速系統(tǒng)的性能。為了簡(jiǎn)化控制系統(tǒng),減少設(shè)備故障率,在矢量控制變頻調(diào)速的基礎(chǔ)上又發(fā)
6、展了無(wú)速度傳感器的矢量控制變頻調(diào)速。在一些對(duì)動(dòng)靜態(tài)特性要求不太高的應(yīng)用中,無(wú)速度傳感器的矢量控制變頻調(diào)速己完全可以和有速度傳感器的矢量控制變頻調(diào)速相媲美。矢量控制對(duì)交流電機(jī)調(diào)速具有劃時(shí)代的意義。</p><p> 變頻調(diào)速是電機(jī)調(diào)速的最佳方式,是企業(yè)技術(shù)改造和產(chǎn)品更新?lián)Q代的理想設(shè)備,是工業(yè)自動(dòng)化系統(tǒng)必不可少的組成部分,是實(shí)現(xiàn)生產(chǎn)過(guò)程和管理自動(dòng)化的前提,也是信息化發(fā)展的先決條件。在我國(guó)傳統(tǒng)產(chǎn)業(yè)中,采用直流電機(jī)拖動(dòng)
7、的調(diào)速系統(tǒng)約占調(diào)速系統(tǒng)總量的85%~90%,而交流調(diào)速系統(tǒng)僅占10%~15%。效率低、質(zhì)量差、消耗大、故障率高己成為制約企業(yè)發(fā)展的瓶頸。因此,必須積極推廣先進(jìn)的交流變頻調(diào)速技術(shù),用先進(jìn)的設(shè)備武裝傳統(tǒng)產(chǎn)業(yè),促進(jìn)自動(dòng)化、工業(yè)化和信息化的進(jìn)一步發(fā)展。</p><p> 1.2 變頻調(diào)速發(fā)展趨勢(shì)</p><p> 如果說(shuō)以第一個(gè)晶閘管的出現(xiàn)作為交流電動(dòng)機(jī)變頻調(diào)速的起點(diǎn),可以認(rèn)為它的發(fā)展歷史己4
8、0多年了。而變頻調(diào)速技術(shù)真正高速發(fā)展時(shí)期,應(yīng)該是在PWM調(diào)制技術(shù)的出現(xiàn)和微機(jī)控制技術(shù)發(fā)展之后。特別是最近20年來(lái),隨著交流調(diào)速技術(shù)的應(yīng)用普及,交流變頻調(diào)速在化工、火電廠、礦山、油田、機(jī)械制造、城市建設(shè)、水處理、甚至家電等行業(yè)己經(jīng)全面推廣使用,一般主要用于節(jié)能及控制。隨著變頻技術(shù)的普及和深入,以及國(guó)際、國(guó)內(nèi)電器設(shè)備使用的有關(guān)標(biāo)準(zhǔn)意識(shí)的強(qiáng)化,電力系統(tǒng)行業(yè)和用戶對(duì)變頻技術(shù)的質(zhì)量要求也越來(lái)越高。變頻調(diào)速的發(fā)展趨勢(shì)主要圍繞下面幾個(gè)方而展開(kāi)。<
9、;/p><p> 1) 高性能的智能控制變頻器</p><p> 380V系統(tǒng)的低壓變頻器是國(guó)內(nèi)的主要研究對(duì)象,應(yīng)用交流調(diào)速的基本理論,結(jié)合神經(jīng)網(wǎng)絡(luò)控制、魯棒控制、模糊控制,或其他智能控制等手段,實(shí)現(xiàn)電機(jī)運(yùn)行參數(shù)的自動(dòng)辨識(shí),以期達(dá)到自適應(yīng)、自調(diào)整的最優(yōu)控制。這方面己有一定的研究成果。</p><p> 2) 速度傳感器研究</p><p>
10、 從前面所述的各種變頻調(diào)速的理論可知,一般系統(tǒng)都要用到轉(zhuǎn)速傳感器。在實(shí)際使用中,由于變頻設(shè)備和被控電動(dòng)機(jī)有一定的距離,而高精度的轉(zhuǎn)速傳感器都要使用專門(mén)的電源,被控電動(dòng)機(jī)有的是在戶外,運(yùn)行工況非常惡劣,要保證速度反饋的準(zhǔn)確性,有時(shí)不得不采取特別措施,因此也會(huì)增加額外費(fèi)用,運(yùn)行的可靠性和控制精度也會(huì)因此受到影響。無(wú)速度傳感器的變頻調(diào)速系統(tǒng),是通過(guò)現(xiàn)場(chǎng)采集的電流電壓量,以及控制的實(shí)施策略,綜合出被控電機(jī)的實(shí)際轉(zhuǎn)速。這種控制方案要求計(jì)算機(jī)的控
11、制速度較高,并有足夠的精度。</p><p> 3) 針對(duì)功率因數(shù)提高和諧波污染的研究</p><p> 低壓變頻調(diào)速系統(tǒng)的控制雖然己經(jīng)是非常成熟了,但目前國(guó)際、國(guó)內(nèi)的產(chǎn)品,一般都是矢量控制和直接轉(zhuǎn)矩控制,重點(diǎn)放在電機(jī)變頻控制理論的實(shí)現(xiàn)和完善上,而對(duì)變頻器的輸出波形、功率因數(shù),以及諧波污染等問(wèn)題還沒(méi)有引起足夠的重視。最近10多年來(lái),國(guó)外在這一領(lǐng)域己有較深入的研究。有的針對(duì)功率因數(shù),有的
12、強(qiáng)調(diào)輸出波形。多重化技術(shù)就是為了解決輸出波形問(wèn)題。最近幾年的研究表明,利用PWM輸出控制解決諧波輸出問(wèn)題,是比較理想的方法,它可以省去多重化中的變壓器,或過(guò)多的開(kāi)關(guān)元器件,使變頻器的體積和重量減少,但這種方法不能解決所有諧波的消除問(wèn)題,只能部分消除特定諧波。這方面的研究論文還不多,也還沒(méi)有成熟的類似低壓變頻器的產(chǎn)品出現(xiàn)。</p><p> 4) 高壓變頻器的研究</p><p> 變頻
13、器的主要作用之一是節(jié)能。而高壓電動(dòng)機(jī)的節(jié)能效果是比較明顯的,大功率的風(fēng)機(jī)和水泵用電動(dòng)機(jī)一般都是高壓電動(dòng)機(jī)。國(guó)內(nèi),高壓變頻調(diào)速和它的節(jié)能控制還是一個(gè)比較薄弱的環(huán)節(jié).它主要是針對(duì)6~10kV的交流電動(dòng)機(jī)進(jìn)行變頻調(diào)速控制。這種高壓電動(dòng)機(jī)廣泛應(yīng)用于火力發(fā)電廠的送風(fēng)機(jī)和引風(fēng)機(jī)上。同樣也可用于其他如石油化工、礦山、冶煉、機(jī)械制造等行業(yè)的變頻節(jié)能控制。從某種意義上講,由于目前國(guó)內(nèi)還不能完全生產(chǎn)高質(zhì)量的合格電力電子器件,而且,國(guó)外低壓變頻器的性能價(jià)格比
14、也比國(guó)內(nèi)自己研究的變頻器高得多。因此,在這方面還有許多研究工作要做。</p><p> 隨著電力電子技術(shù)最近20多年的飛速發(fā)展,功率半導(dǎo)體器件的成本逐年下降,技術(shù)工藝和性能也得到不斷改善.電力電子器件的應(yīng)用己從傳統(tǒng)的直流調(diào)速、直流屏、斬波器等領(lǐng)域延伸到交流調(diào)速和電力系統(tǒng)的質(zhì)量控制領(lǐng)域.并正朝著高電壓、大功率的方向發(fā)展.這也是千年之交和世紀(jì)之交我國(guó)電力電子技術(shù)應(yīng)用的發(fā)展趨勢(shì)。</p><p&g
15、t; 5) 無(wú)換向器同步電機(jī)的變頻調(diào)速</p><p> 無(wú)換向器電動(dòng)機(jī)也是在20世紀(jì)70年代發(fā)展起來(lái)的新型調(diào)速系統(tǒng)。它是一種變頻調(diào)速同步電動(dòng)機(jī).也可以認(rèn)為是一種用半導(dǎo)體電子開(kāi)關(guān)線路代替換向器和電刷作用的直流電動(dòng)機(jī)。根據(jù)采用的控制方式不同.可分為直流無(wú)換向器電動(dòng)機(jī)和交流無(wú)換向器電動(dòng)機(jī)。直流無(wú)換向器電動(dòng)機(jī)采用交-直-交或直-交變頻控制系統(tǒng);交流無(wú)換向器電動(dòng)機(jī)采用交-交變頻控制系統(tǒng)。近10年來(lái).國(guó)內(nèi)外雜志上有許多
16、相關(guān)的研究論文。而且,也有一定的成果出現(xiàn)。</p><p> 1.3 變頻調(diào)速控制方式</p><p> 交流變頻調(diào)速技術(shù)在20世紀(jì)得到了迅速發(fā)展。這與一些關(guān)鍵性技術(shù)的突破性進(jìn)展有關(guān),它們是交流電動(dòng)機(jī)的矢量控制技術(shù)、直接轉(zhuǎn)矩控制技術(shù)、PWM技術(shù)以及微型計(jì)算機(jī)和大規(guī)模集成電路為基礎(chǔ)的全數(shù)字化控制技術(shù)、自整定技術(shù)等。</p><p><b> 1) 矢量
17、控制技術(shù)</b></p><p> 矢量變換控制技術(shù)是西門(mén)子公司于1971年提出的一種新的控制思想和控制理論。它是以轉(zhuǎn)子磁場(chǎng)定向,采用矢量變換的方法實(shí)現(xiàn)定子電流勵(lì)磁分量和轉(zhuǎn)矩分量之間的解藕,達(dá)到對(duì)交流電動(dòng)機(jī)的磁鏈和電流分別控制的目的,從而獲得了優(yōu)良的靜、動(dòng)態(tài)性能。迄今為止,矢量控制技術(shù)己經(jīng)獲得了長(zhǎng)足的發(fā)展,并得到了廣泛應(yīng)用。</p><p> 2) 無(wú)速度傳感器矢量控制技術(shù)
18、</p><p> 無(wú)速度傳感器控制技術(shù)免去了傳感器帶來(lái)的環(huán)境適應(yīng)性、安裝維護(hù)等問(wèn)題,降低了成本,提高了系統(tǒng)的可靠性,同時(shí)結(jié)合矢量控制,具有矢量控制的優(yōu)良性能。無(wú)速度傳感器技術(shù)中速度估算的方法,除了根據(jù)數(shù)學(xué)模型計(jì)算電動(dòng)機(jī)轉(zhuǎn)速外,目前應(yīng)用較多的有模型參考自適應(yīng)法和擴(kuò)展卡爾曼濾波法。此外全維轉(zhuǎn)子磁通觀測(cè)器,齒諧波電勢(shì)(RSH)等理論也出現(xiàn)在無(wú)速度傳感器技術(shù)中。從1983年提出無(wú)速度傳感器矢量控制策略以來(lái),一直受到學(xué)
19、術(shù)界和產(chǎn)業(yè)界的高度重視,日立、安川電機(jī)等公司在1987年分別發(fā)表了研究成果,并相繼推出了產(chǎn)品。目前,無(wú)速度傳感器矢量控制變頻器的調(diào)速范圍為1:50左右,個(gè)別廠商有1:75甚至更高的產(chǎn)品。</p><p> 3) 直接轉(zhuǎn)矩控制技術(shù)</p><p> 1985年.德國(guó)的M . Depen-block首次提出直接轉(zhuǎn)矩控制技術(shù)(DTC)。DTC控制直接在定子坐標(biāo)系下分析交流電動(dòng)機(jī)的數(shù)學(xué)模型。采
20、用定子磁場(chǎng)定向而無(wú)需解藕電流,直接控制電動(dòng)機(jī)的磁鏈和轉(zhuǎn)矩,以使轉(zhuǎn)矩得到快速響應(yīng),從而獲得高效的控制性能。</p><p> 直接轉(zhuǎn)矩控制技術(shù)是近10年繼矢量控制技術(shù)之后發(fā)展起來(lái)的又一種新型的高性能交流變頻調(diào)速技術(shù),這種控制技術(shù)與矢量控制技術(shù)相比,對(duì)電機(jī)參數(shù)不敏感,不受轉(zhuǎn)子參數(shù)的影響,簡(jiǎn)單易行,具有廣闊的發(fā)展和應(yīng)用前景。</p><p> 4) PWM控制技術(shù)</p>&l
21、t;p> 1964年,德國(guó)的A. Schonung等率先提出了脈寬調(diào)制(PWM -pulse width modulation)變頻的思想,為近代交流調(diào)速系統(tǒng)開(kāi)辟了新的發(fā)展領(lǐng)域。PWM控制技術(shù)通過(guò)改變矩形脈沖的寬度來(lái)控制逆變器輸出交流基波電壓的幅值,通過(guò)改變調(diào)制周期來(lái)控制其輸出頻率,從而在逆變器上同時(shí)進(jìn)行輸出電壓幅值和頻率的控制。PWM技術(shù)簡(jiǎn)化了逆變器的結(jié)構(gòu),能夠明顯的改善變頻器的輸出波形,降低電動(dòng)機(jī)的諧波損耗,并減小轉(zhuǎn)矩脈動(dòng),
22、同時(shí)提高了系統(tǒng)的動(dòng)態(tài)響應(yīng)性能。PWM技術(shù)還可用于整流器的控制,能夠?qū)崿F(xiàn)輸入電流非常接近正弦.。并可使電網(wǎng)功率因數(shù)為1。PWM整流器因而被稱為“綠色”變流器。目前,PWM技術(shù)己成為變頻器中應(yīng)用最為廣泛的控制技術(shù)。交流電機(jī)調(diào)速性能的不斷提高在很大程度上是由于PWM技術(shù)的不斷進(jìn)步。目前廣泛應(yīng)用的是在規(guī)則采樣PWM的基礎(chǔ)上發(fā)展起來(lái)的準(zhǔn)優(yōu)化PWM法,即三次諧波疊加法和電壓空間矢量PWM法。</p><p> 5) 數(shù)字化
23、控制技術(shù)</p><p> 控制技術(shù)的數(shù)字化是靜止變頻裝置的核心技術(shù),也是今后的發(fā)展趨勢(shì)。目前市場(chǎng)上的變頻裝置幾乎全面實(shí)現(xiàn)了數(shù)字化控制。采用DSP和ASIC技術(shù)實(shí)現(xiàn)了快速運(yùn)算和高精度控制,可以得到良好的電流波形,使變頻器的噪音大幅度降低,并且掃描時(shí)間大幅度縮短,目前電流響應(yīng)為0.1~0.7ms,速度響應(yīng)為2~4 ms,足以滿足傳動(dòng)領(lǐng)域的控制要求。同時(shí)由于應(yīng)用微電子技術(shù)和ASIC技術(shù),裝置的元器件數(shù)量得以大幅度減
24、少,從而使變頻裝置的體積減小,可靠性得到大幅度提高。全數(shù)字控制方式使變頻器的信息處理能力大為增強(qiáng)。采用模擬控制方式無(wú)法實(shí)現(xiàn)的復(fù)雜控制在今天都己成為現(xiàn)實(shí),從而所謂的RAS概念即可靠性(Reliability)、可操作性(Availability)、可維修性(Serviceability)得以充實(shí)。</p><p><b> 6) 自整定技術(shù)</b></p><p>
25、 自整定技術(shù)在變頻調(diào)速系統(tǒng)中的應(yīng)用日益廣泛,它可以根據(jù)速度和負(fù)載的變化自動(dòng)調(diào)整控制系統(tǒng)的參數(shù),使得系統(tǒng)具有快速的動(dòng)態(tài)響應(yīng)。自整定技術(shù)分為離線式和在線式兩種。離線式的研究成果己經(jīng)在相當(dāng)多的產(chǎn)品中應(yīng)用,它是在運(yùn)行系統(tǒng)程序之前通過(guò)運(yùn)行一段自整定程序,辨識(shí)相關(guān)數(shù)據(jù),并修改系統(tǒng)程序的相關(guān)參數(shù),以期獲得良好的系統(tǒng)控制性能。另外,改進(jìn)控制技術(shù),提高系統(tǒng)魯棒性也和自整定技術(shù)緊密相聯(lián)系。</p><p> 2 PLC抗干擾分析&
26、lt;/p><p> 隨著科學(xué)技術(shù)的發(fā)展,PLC在工業(yè)控制中的應(yīng)用越來(lái)越廣泛。PLC控制系統(tǒng)的可靠性直接影響到工業(yè)企業(yè)的安全生產(chǎn)和經(jīng)濟(jì)運(yùn)行,系統(tǒng)的抗干擾能力是關(guān)系到整個(gè)系統(tǒng)可靠運(yùn)行的關(guān)鍵。自動(dòng)化系統(tǒng)中所使用的各種類型PLC,有的是集中安裝在控制室,有的是安裝在生產(chǎn)現(xiàn)場(chǎng)和各電機(jī)設(shè)備上,它們大多處在強(qiáng)電電路和強(qiáng)電設(shè)備所形成的惡劣電磁環(huán)境中。要提高PLC控制系統(tǒng)可靠性,一方面要求PLC生產(chǎn)廠家用提高設(shè)備的抗干擾能力;另一
27、方面,要求工程設(shè)計(jì)、安裝施工和使用維護(hù)中引起高度重視,多方配合才能完善解決問(wèn)題,有效地增強(qiáng)系統(tǒng)的抗干擾性能。 </p><p> 2.1 干擾源及干擾一般分類</p><p> 影響PLC控制系統(tǒng)的干擾源與一般影響工業(yè)控制設(shè)備的干擾源一樣,大都產(chǎn)生在電流或電壓劇烈變化的部位,這些電荷劇烈移動(dòng)的部位就是噪聲源,即干擾源。 </p><p> 干擾類型通常按干擾產(chǎn)
28、生的原因、噪聲干擾模式和噪聲的波形性質(zhì)的不同劃分。其中:按噪聲產(chǎn)生的原因不同,分為放電噪聲、浪涌噪聲、高頻振蕩噪聲等;按噪聲的波形、性質(zhì)不同,分為持續(xù)噪聲、偶發(fā)噪聲等;按噪聲干擾模式不同,分為共模干擾和差模干擾。共模干擾和差模干擾是一種比較常用的分類方法。共模干擾是信號(hào)對(duì)地的電位差,主要由電網(wǎng)串入、地電位差及空間電磁輻射在信號(hào)線上感應(yīng)的共態(tài)(同方向)電壓迭加所形成。共模電壓有時(shí)較大,特別是采用隔離性能差的配電器供電室,變送器輸出信號(hào)的共
29、模電壓普遍較高,有的可高達(dá)130V以上。共模電壓通過(guò)不對(duì)稱電路可轉(zhuǎn)換成差模電壓,直接影響測(cè)控信號(hào),造成元器件損壞(這就是一些系統(tǒng)I/O模件損壞率較高的主要原因),這種共模干擾可為直流、亦可為交流。差模干擾是指作用于信號(hào)兩極間的干擾電壓,主要由空間電磁場(chǎng)在信號(hào)間耦合感應(yīng)及由不平衡電路轉(zhuǎn)換共模干擾所形成的電壓,這種讓直接疊加在信號(hào)上,直接影響測(cè)量與控制精度。 </p><p> 2.2 PLC控制系統(tǒng)中電磁干擾的主
30、要來(lái)源 </p><p> 1) 來(lái)自空間的輻射干擾 </p><p> 空間的輻射電磁場(chǎng)(EMI)主要是由電力網(wǎng)絡(luò)、電氣設(shè)備的暫態(tài)過(guò)程、雷電、無(wú)線電廣播、電視、雷達(dá)、高頻感應(yīng)加熱設(shè)備等產(chǎn)生的,通常稱為輻射干擾,其分布極為復(fù)雜。若PLC系統(tǒng)置于所射頻場(chǎng)內(nèi),就回收到輻射干擾,其影響主要通過(guò)兩條路徑:一是直接對(duì)PLC內(nèi)部的輻射,由電路感應(yīng)產(chǎn)生干擾;而是對(duì)PLC通信內(nèi)網(wǎng)絡(luò)的輻射,由通信線路的
31、感應(yīng)引入干擾。輻射干擾與現(xiàn)場(chǎng)設(shè)備布置及設(shè)備所產(chǎn)生的電磁場(chǎng)大小,特別是頻率有關(guān),一般通過(guò)設(shè)置屏蔽電纜和PLC局部屏蔽及高壓泄放元件進(jìn)行保護(hù)。 </p><p> 2) 來(lái)自系統(tǒng)外引線的干擾 </p><p> 主要通過(guò)電源和信號(hào)線引入,通常稱為傳導(dǎo)干擾。這種干擾在我國(guó)工業(yè)現(xiàn)場(chǎng)較嚴(yán)重。 </p><p> 3) 來(lái)自電源的干擾 </p>
32、<p> 實(shí)踐證明,因電源引入的干擾造成PLC控制系統(tǒng)故障的情況很多,筆者在某工程調(diào)試中遇到過(guò),后更換隔離性能更高的PLC電源,問(wèn)題才得到解決。 </p><p> PLC系統(tǒng)的正常供電電源均由電網(wǎng)供電。由于電網(wǎng)覆蓋范圍廣,它將受到所有空間電磁干擾而在線路上感應(yīng)電壓和電路。尤其是電網(wǎng)內(nèi)部的變化,入開(kāi)關(guān)操作浪涌、大型電力設(shè)備起停、交直流傳動(dòng)裝置引起的諧波、電網(wǎng)短路暫態(tài)沖擊等,都通過(guò)輸電線路傳到電源原邊
33、。PLC電源通常采用隔離電源,但其機(jī)構(gòu)及制造工藝因素使其隔離性并不理想。實(shí)際上,由于分布參數(shù)特別是分布電容的存在,絕對(duì)隔離是不可能的。 </p><p> 4) 來(lái)自信號(hào)線引入的干擾 </p><p> 與PLC控制系統(tǒng)連接的各類信號(hào)傳輸線,除了傳輸有效的各類信息之外,總會(huì)有外部干擾信號(hào)侵入。此干擾主要有兩種途徑:一是通過(guò)變送器供電電源或共用信號(hào)儀表的供電電源串入的電網(wǎng)干擾
34、,這往往被忽視;二是信號(hào)線受空間電磁輻射感應(yīng)的干擾,即信號(hào)線上的外部感應(yīng)干擾,這是很嚴(yán)重的。由信號(hào)引入干擾會(huì)引起I/O信號(hào)工作異常和測(cè)量精度大大降低,嚴(yán)重時(shí)將引起元器件損傷。對(duì)于隔離性能差的系統(tǒng),還將導(dǎo)致信號(hào)間互相干擾,引起共地系統(tǒng)總線回流,造成邏輯數(shù)據(jù)變化、誤動(dòng)和死機(jī)。PLC控制系統(tǒng)因信號(hào)引入干擾造成I/O模件損壞數(shù)相當(dāng)嚴(yán)重,由此引起系統(tǒng)故障的情況也很多。 </p><p> 5) 來(lái)自接地系統(tǒng)混亂時(shí)的干擾&
35、#160; </p><p> 接地是提高電子設(shè)備電磁兼容性(EMC)的有效手段之一。正確的接地,既能抑制電磁干擾的影響,又能抑制設(shè)備向外發(fā)出干擾;而錯(cuò)誤的接地,反而會(huì)引入嚴(yán)重的干擾信號(hào),使PLC系統(tǒng)將無(wú)法正常工作。 </p><p> PLC控制系統(tǒng)的地線包括系統(tǒng)地、屏蔽地、交流地和保護(hù)地等。接地系統(tǒng)混亂對(duì)PLC系統(tǒng)的干擾主要是各個(gè)接地點(diǎn)電位分布不均,不同接地點(diǎn)間存在地電位差,引起地
36、環(huán)路電流,影響系統(tǒng)正常工作。例如電纜屏蔽層必須一點(diǎn)接地,如果電纜屏蔽層兩端A、B都接地,就存在地電位差,有電流流過(guò)屏蔽層,當(dāng)發(fā)生異常狀態(tài)如雷擊時(shí),地線電流將更大。</p><p> 6) 來(lái)自PLC系統(tǒng)內(nèi)部的干擾 </p><p> 主要由系統(tǒng)內(nèi)部元器件及電路間的相互電磁輻射產(chǎn)生,如邏輯電路相互輻射及其對(duì)模擬電路的影響,模擬地與邏輯地的相互影響及元器件間的相互不匹配使用等。這都屬于PL
37、C制造廠對(duì)系統(tǒng)內(nèi)部進(jìn)行電磁兼容設(shè)計(jì)的內(nèi)容,比較復(fù)雜,作為應(yīng)用部門(mén)是無(wú)法改變,可不必過(guò)多考慮,但要選擇具有較多應(yīng)用實(shí)績(jī)或經(jīng)過(guò)考驗(yàn)的系統(tǒng)。</p><p> 此外,屏蔽層、接地線和大地有可能構(gòu)成閉合環(huán)路,在變化磁場(chǎng)的作用下,屏蔽層內(nèi)有會(huì)出現(xiàn)感應(yīng)電流,通過(guò)屏蔽層與芯線之間的耦合,干擾信號(hào)回路。若系統(tǒng)地與其它接地處理混亂,所產(chǎn)生的地環(huán)流就可能在地線上產(chǎn)生不等電位分布,影響PLC內(nèi)邏輯電路和模擬電路的正常工作。PLC工作
38、的邏輯電壓干擾容限較低,邏輯地電位的分布干擾容易影響PLC的邏輯運(yùn)算和數(shù)據(jù)存貯,造成數(shù)據(jù)混亂、程序跑飛或死機(jī)。模擬地電位的分布將導(dǎo)致測(cè)量精度下降,引起對(duì)信號(hào)測(cè)控的嚴(yán)重失真和誤動(dòng)作。 </p><p><b> 附錄B</b></p><p><b> 外文文獻(xiàn)</b></p><p> 1 Frequency Var
39、iation Speed Control</p><p> 1.1 The Popularity and Prospect of Frequency Variation Speed Control</p><p> The electrical machinery exchange frequency conversion velocity modulation technology
40、is the electricity saving, the improvement technical process improves the product quality and the improvement environment, the impetus technology advancement one main method now The frequency conversion velocity modulati
41、on by its outstanding velocity modulation and the braking quality, the high efficiency, the high power factor and the electricity saving effect, the widespread applicable scope and other many me</p><p> In
42、recent years exchanged in the velocity modulation most to be active, to develop quickest is the frequency conversion velocity modulation technology, the frequency conversion velocity modulation is exchanges the velocity
43、modulation foundation and the branch content. The last century transformer appearance causes the change voltage to become very much easy, thus has accomplished a huge electric power profession. Since long ago, the altern
44、ating current frequency always is fixed, the frequency co</p><p> In this recent 10 years, the frequency conversion technology application has the very big development in our country, and obtained the good
45、effect to be possible to say, the frequency conversion technology has accepted for the majority users, but had no alternative but to point out, our country in frequency conversion technology application aspect, with deve
46、loped country level Shang You very big disparity. At present, the AC motors we are using now use frequency variation speed control only abou</p><p> And with the constant development of control technique an
47、d control avenue, frequency variation speed controlled has developed the vector controlled frequency variation velocity modulation, by controlling the AC motor inside act for shunt DC motor field coper’s flux, to enhance
48、 the permanent torque output scope and static and dynamic character, make the AC motor frequency variation speed controlled system superior to DC motor voltage variation speed controlled system. For simplifying the contr
49、ol </p><p> Frequency variation speed control is the best way in the motor speed modulation, it is the perfect gear in the company’s technical reform and product renewal, it is the essential composition in
50、the industrial automatic system, it is the assumption of realizing the automatic of product proceed and management, it is also the precondition in the development of informationization. In our country’s traditional estat
51、e, using the DC motor speed control actuation account about 85%~90% in the speed contr</p><p> 1.2 Our Country’s Development Condition in Speed Controlled Technique</p><p> Our country is a de
52、veloping country, so many product’s research ability has behind the developed countries. From now on, the product of frequency variation speed controlled that ourselves made only act for last century 90s in the internati
53、onal. With the reform and opening, rapid development of economic, forms a large market, it opens to the country companies, also the foreign companies. Many products are exported from the developed countries, and runs wel
54、l in our country, satisfied our need in f</p><p> As early as in the country "85" technical attack plan, the alternating velocity modulation technique was listed as the key technical attack projec
55、t, but because our country’s electric power and electronic device aggregate level is very low, although the production of IGBT、GTO component has introduced the overseas technique, it has not formed the economies of scale
56、 benefit, almost does not have the independent development ability of new frequency converter production, this has affected the domest</p><p> Therefore, the AC frequency variation speed control technique h
57、as the following sides:</p><p> 1) The basic research of control strategy in frequency converter has a large gap compares with the foreign level.</p><p> 2) The technical level of the whole ma
58、chine is low in the frequency converter, although we had input certainly people, material resources, but because of the disperse power, did not form a certainly technique and production scale.</p><p> 3) Al
59、l the semiconductor power device product in the frequency converter is blank.</p><p> 4) Correlative Industries and relative Industries drop behind.</p><p> 5) Few production and sale, low rel
60、iable and technological standards.</p><p> With the development and improvement in the power electronic technique, power divert based on power electronic circuit technique and various control technique, the
61、 AC frequency variation speed controlled technique is mature day by day, and sure to be the main way in the future. With the constant development of power electronic technique, reliable character, well adoption, cheap pr
62、ice that the frequency converter have will become true. This technique will gain widely, popularity application .At p</p><p> 1.3 Frequency Variation Speed Controlled Mode</p><p> The alternat
63、ing frequency conversion velocity modulation technique obtained the rapid development in 20th century. This is related with some crucial technical which gain unprecedented progress, they are Motor vector control techniqu
64、e, Direct torque control technique, PWM technique, Entire numerical control technique and self-setting technique which based on microcomputer and large scale integrated circuit, and so on.</p><p> 1) Vector
65、 Control Technique</p><p> Vector transformation control technique is a one kind of new control thought and control theory which posed by SIEMENS CO. in 1971. It is realizing the stator current excitation c
66、omponent and the torque component solution lotus root by rotor magnetic field direction detection, and vector transformation, achieved the goal that separately control the motor flux linkage and the electric current, as
67、a result, obtain finely static, dynamic performance. Until now, the vector control technique has obta</p><p> 2) Vector Control Without Velocity Generator Technique</p><p> Vector control with
68、out velocity generator technique abolish the problems that the environment compatibility、install and maintenance bring on, reduce the cost, enhance the system reliability, at the same time, union vector control, has the
69、fine performance of vector control. The speed estimate method in vector control technique without velocity generator, besides basis mathematical model computation electric motor rotational speed, at present the more appl
70、ied are the model to refer auto-adapted m</p><p> 3) Direct Torque Control Technique</p><p> In1985, Germany's M. Depen-block proposes the direct torque control technique(DTC) for the firs
71、t time,The direct torque control technique analyzes the motor mathematical model directly under the stator coordinate system. Uses the stator magnetic field direction detection but not to need the solution lotus root ele
72、ctric current,directly control the electric motor flux linkage and torque, enable the torque to obtain the fast response, in order to obtain the highly effective control performance.</p><p> Direct torque c
73、ontrol technique is another kind of new、high performance alternating frequency conversion velocity modulation technique after vector control technique in the nearly 10 years, this kind of control technique is insensitive
74、 to the electrical machinery parameter, not influence by the rotor parameter, easy and feasible, it has the broad development and the application prospect.</p><p> 4) PWM (pulse width modulation) Control Te
75、chnique</p><p> In1964, Germany's A. Schonung and some people took the lead to propose the pulse-duration modulation (PWM -pulse width modulation) frequency conversion thought, opened the recent develop
76、ment domain for the modern alternating velocity modulation system. The PWM control technique controls the inversion output alternating fundamental wave voltage peak-to-peak value by changing the rectangle pulse width, co
77、ntrols its output frequency through changing the modulation cycle, in order to carry on the ou</p><p> 5) Numerical Control Technique</p><p> The digitalize in control technique is the key tec
78、hnique of static frequency conversion installment, also will be the next development tendency, at present in the market frequency conversion installment nearly comprehensively has realized the numerical control. Has real
79、ized the fast operation and the high accuracy control by using the DSP and the ASIC technique, and could gain a fine current wave, reduce the noise of the frequency converter in a large scale, and the scanning time also
80、be reduced</p><p> 6) Self-setting Technique</p><p> The self-setting technique is widespread used in the frequency conversion velocity modulation system day by day, it may accord to the speed
81、 and the load to auto adjust the parameter of the control system, enable the system with rapid dynamic response. The self-setting technique divides into off-line and the on-line. The research results in the kind of off-l
82、ine has been applied in the most production, before the system program operate, it operate a block self-setting program, recognize the correl</p><p> 2 PLC interference analysis </p><p> With
83、the development of science and technology, the application in industrial control of PLC is more and more extensive. The dependability of PLC control system influences the safety in production and economical operation of
84、the industrial enterprise directly; systematic anti-interference ability is the key to concerning the whole system and running reliably. All kinds of PLC used in the automated system, some install concentrated in the con
85、trol room , some install in production scene and every </p><p> 2.1 Sources of interference and interference with the general classification </p><p> It is like generally influencing the inter
86、ference source of the industrial control equipment to influence the interference source of PLC control system, mostly producing the position in the electric current or violent change of voltage, these violent position th
87、at move of electric charge is the noise source, namely interfere the source.</p><p> Interfere type interfere the division different from wave form nature of the noise of the mode according to reason, noise
88、 produced to interfere usually. Among them: According to reason that noise produce being different, is it discharge noise, wave well up noise, high frequency shake noise, etc. to divide into; Different according to the w
89、ave form, nature of the noise, divided into a lasting noise, accidental noiseless.; It is different to interfere the mode according to the noise, is divided in</p><p> 2.2 PLC control system electromagnetic
90、 interference the main source</p><p> 1) The radiation from space interference </p><p> mainly produced by temporary attitude course , thunder and lightning , radio broadcasting , TV,radar, hi
91、gh-frequency reaction heating device of the electric network , electric equipment ,etc., usually called radiation to interfere, it is extremely complicated that it is distributed. Whether if PLC system put on radio frequ
92、ency in the field is it reaches radiation interfere to retrieve, it influences and mainly passes two routes. First, produced and interferes by the reaction of the circuit to th</p><p> 2) Interference from
93、lead wire outside the system</p><p> Introduce through the power and signal line mainly, is usually called and conducted interfering. This kind of interference is relatively serious at the industrial scene
94、of our country.</p><p> 3) Interference from power</p><p> Practice has proved , interference introduced because of the power causes situations of PLC control system trouble a lot of, I meet i
95、n debugging in some project, is it isolate performance high PLC power to change, the problem is solved .</p><p> Normal power supply power, PLC of system supply power by the electric wire netting. Because t
96、he electric wire netting is widely covered, it will be interfered the voltage of reaction and circuit on the circuit electromagnetically by all space. Change of electric wire netting, enter switch operate wave well up, l
97、arge-scale electric equipment is it park, is it is it move in harmony wave, electric wire netting that device cause short out the attitude is bludgeoned into etc. temporarily to spread di</p><p> 4) Come fr
98、om the interference that the signal thread introduces</p><p> All kinds of signal transmission lines connected with PLC control system, besides transmitting all kinds of effective information, always there
99、will be outside interfering signals that will be invaded. This interference has two kinds of ways mainly: Supply power or share through changer power supply power a bunch of electric wire netting entered, signal of instr
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