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變頻器高次諧波產生原因、危害和處理方法

閱讀次數:971    發布時間: 2021-11-12 10:50:18

隨著電力(li)電子技術的(de)發展(zhan),變頻器在電力(li)電子系統、工(gong)業(ye)等諸多(duo)領域中的(de)應用日(ri)益(yi)廣泛,變頻器產(chan)生的(de)高次諧波對公(gong)用電網產(chan)生的(de)危害(hai)也(ye)日(ri)益(yi)嚴(yan)重。

高次諧波的危害

1)使電網中的元(yuan)件(jian)產生附(fu)加(jia)的諧(xie)波損耗,降低(di)發電、輸電及用電設備的效率,大量(liang)的3次諧(xie)波流過中性線會(hui)使線路過熱甚至(zhi)發生火災;

2)影響各(ge)種電(dian)器設(she)備的正常工作(zuo),使(shi)電(dian)機發(fa)生(sheng)機械(xie)振(zhen)動、噪(zao)聲(sheng)和過(guo)熱,使(shi)變壓器局部嚴重過(guo)熱,使(shi)電(dian)容器、電(dian)纜等設(she)備過(guo)熱,使(shi)絕緣(yuan)老化,壽命縮短以至損壞;

3)引起電(dian)網中局部的并聯諧振和(he)串(chuan)聯諧振,從而使(shi)諧波放大,引起嚴重事故;

4)對鄰近的(de)通(tong)(tong)信(xin)系統產生(sheng)干擾,輕(qing)者產生(sheng)噪(zao)聲,降低通(tong)(tong)信(xin)質量,重(zhong)者導致信(xin)息丟失(shi),使通(tong)(tong)信(xin)系統無法正常工作(zuo);

5)導(dao)致繼電保護和自動裝置的誤動作,并使電氣(qi)測(ce)量儀表計量不準確。

由(you)(you)(you)于公用(yong)(yong)電(dian)(dian)網(wang)中的(de)諧波(bo)電(dian)(dian)壓和(he)諧波(bo)電(dian)(dian)流對用(yong)(yong)電(dian)(dian)設備和(he)電(dian)(dian)網(wang)本身(shen)都造成很大的(de)危害,世界許多(duo)國(guo)家多(duo)發布了限制電(dian)(dian)網(wang)諧波(bo)的(de)國(guo)家標準(zhun),由(you)(you)(you)權威機構(gou)制定(ding)限制諧波(bo)的(de)規定(ding)。世界各國(guo)制定(ding)的(de)諧波(bo)標準(zhun)大都比較(jiao)接近(jin)。我國(guo)由(you)(you)(you)技術監(jian)督局于1993年(nian)(nian)發布了國(guo)家標準(zhun)(GB/T14549-93)<<電(dian)(dian)能(neng)質(zhi)量公用(yong)(yong)電(dian)(dian)網(wang)諧波(bo)>>,并從1994年(nian)(nian)3月(yue)1日起開始實施。

變頻器的諧波

變(bian)頻器是工(gong)業調速傳動(dong)領域中應(ying)用(yong)較(jiao)為(wei)廣泛的(de)(de)設備之一。變(bian)頻器是把工(gong)頻(50Hz)變(bian)換(huan)成(cheng)各種頻率(lv)的(de)(de)交(jiao)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)源,以實現(xian)電(dian)(dian)(dian)(dian)機的(de)(de)變(bian)速運行的(de)(de)設備。其中控(kong)制電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)完成(cheng)對(dui)主電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)的(de)(de)控(kong)制,整(zheng)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)將(jiang)交(jiao)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)轉(zhuan)換(huan)成(cheng)直流(liu)(liu)(liu)電(dian)(dian)(dian)(dian),直流(liu)(liu)(liu)中間電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)對(dui)整(zheng)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)的(de)(de)輸出進(jin)行平滑(hua)濾波,逆變(bian)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)將(jiang)直流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)再(zai)逆變(bian)成(cheng)交(jiao)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)。

由(you)于變(bian)頻器(qi)逆變(bian)電(dian)路的開關特(te)性(xing),對其(qi)供電(dian)電(dian)源(yuan)形成了一個(ge)典型的非(fei)線性(xing)負載,因此,以變(bian)頻器(qi)為代表的電(dian)力電(dian)子裝置是公用(yong)電(dian)網中最主要的諧波源(yuan)之一。

諧波(bo)是(shi)指對(dui)周期性非(fei)正弦交流量(liang)(liang)進行傅里葉級數分(fen)解所(suo)得(de)到的大(da)于基波(bo)頻率整數倍的各次分(fen)量(liang)(liang),通常也(ye)稱(cheng)為高次諧波(bo),而基波(bo)是(shi)指其頻率與工(gong)頻相同的分(fen)量(liang)(liang)。

就電(dian)力(li)系(xi)統中的(de)(de)三(san)相交流發(fa)電(dian)機發(fa)出的(de)(de)電(dian)壓來說,可以認為其波(bo)形(xing)基(ji)本(ben)上(shang)是(shi)正弦(xian)量(liang),即電(dian)壓波(bo)形(xing)基(ji)本(ben)上(shang)無直流和諧(xie)(xie)波(bo)分量(liang)。但由于電(dian)力(li)系(xi)統中存在(zai)(zai)著(zhu)各種(zhong)各樣的(de)(de)諧(xie)(xie)波(bo)源(yuan)(諧(xie)(xie)波(bo)源(yuan)是(shi)指向公(gong)用電(dian)網注入諧(xie)(xie)波(bo)電(dian)流或(huo)在(zai)(zai)公(gong)用電(dian)網中產生諧(xie)(xie)波(bo)電(dian)壓的(de)(de)電(dian)氣設備(bei)),特(te)別(bie)是(shi)變流裝置等設備(bei)。

其中(zhong)(zhong),變(bian)(bian)頻(pin)器(qi)的(de)(de)輸入側(ce)(ce)產生諧波(bo)(bo)(bo)的(de)(de)機(ji)(ji)理是(shi):凡是(shi)在(zai)(zai)(zai)電(dian)(dian)(dian)(dian)源(yuan)側(ce)(ce)有(you)整(zheng)流(liu)(liu)回路(lu)(lu)的(de)(de)都產生因(yin)其非(fei)線性(xing)引起的(de)(de)諧波(bo)(bo)(bo)。而變(bian)(bian)頻(pin)器(qi)輸出(chu)側(ce)(ce)產生諧波(bo)(bo)(bo)的(de)(de)機(ji)(ji)理是(shi):在(zai)(zai)(zai)逆變(bian)(bian)電(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)(zhong),對(dui)于(yu)電(dian)(dian)(dian)(dian)壓(ya)(ya)型電(dian)(dian)(dian)(dian)路(lu)(lu)來說,輸出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)是(shi)矩形(xing)波(bo)(bo)(bo)。對(dui)電(dian)(dian)(dian)(dian)流(liu)(liu)型電(dian)(dian)(dian)(dian)路(lu)(lu)來說,輸出(chu)電(dian)(dian)(dian)(dian)流(liu)(liu)是(shi)矩形(xing)波(bo)(bo)(bo)。矩形(xing)波(bo)(bo)(bo)中(zhong)(zhong)含有(you)較多(duo)的(de)(de)諧波(bo)(bo)(bo),對(dui)負載會產生不利影響,因(yin)此(ci)即使電(dian)(dian)(dian)(dian)力(li)系(xi)統中(zhong)(zhong)電(dian)(dian)(dian)(dian)源(yuan)的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)是(shi)正弦波(bo)(bo)(bo),也(ye)會由于(yu)非(fei)線性(xing)元件的(de)(de)存(cun)(cun)在(zai)(zai)(zai)使得電(dian)(dian)(dian)(dian)網中(zhong)(zhong)總有(you)諧波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)流(liu)(liu)或電(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)存(cun)(cun)在(zai)(zai)(zai)。因(yin)此(ci),電(dian)(dian)(dian)(dian)網諧波(bo)(bo)(bo)的(de)(de)存(cun)(cun)在(zai)(zai)(zai)主要在(zai)(zai)(zai)于(yu)電(dian)(dian)(dian)(dian)力(li)系(xi)統中(zhong)(zhong)存(cun)(cun)在(zai)(zai)(zai)各種非(fei)線性(xing)元件。

治理方法

目前諧(xie)波的治理(li)可采(cai)用以(yi)下方法:

(1)變頻(pin)器的(de)隔離、屏蔽、接地(di)

變頻器(qi)系統的(de)(de)供電(dian)電(dian)源(yuan)與其它設(she)(she)備(bei)的(de)(de)供電(dian)電(dian)源(yuan)相互獨立;或在變頻器(qi)和其它用電(dian)設(she)(she)備(bei)的(de)(de)輸入側安裝隔離變壓器(qi);或者(zhe)將變頻器(qi)放(fang)入鐵箱內,鐵箱外殼接(jie)地(di)。同時變頻器(qi)輸出電(dian)源(yuan)應盡量(liang)遠離控制(zhi)電(dian)纜(lan)敷設(she)(she)(不小于50mm間距),必(bi)須靠近敷設(she)(she)時盡量(liang)以正(zheng)交(jiao)角度跨越,必(bi)須平行敷設(she)(she)時盡量(liang)縮短平行段長(chang)度(不超(chao)過1mm),輸出電(dian)纜(lan)應穿鋼(gang)管并將鋼(gang)管作電(dian)氣連通(tong)并可靠接(jie)地(di)。

(2)加裝交流(liu)(liu)電抗器和直流(liu)(liu)電抗器

當(dang)變(bian)頻(pin)(pin)器(qi)(qi)(qi)使用在(zai)配電(dian)(dian)(dian)(dian)變(bian)壓(ya)器(qi)(qi)(qi)容量大(da)于(yu)500KVA,且變(bian)壓(ya)器(qi)(qi)(qi)容量大(da)于(yu)變(bian)頻(pin)(pin)器(qi)(qi)(qi)容量的(de)10倍(bei)以上(shang),則在(zai)變(bian)頻(pin)(pin)器(qi)(qi)(qi)輸(shu)(shu)入側加(jia)裝交流電(dian)(dian)(dian)(dian)抗(kang)器(qi)(qi)(qi)。而當(dang)配電(dian)(dian)(dian)(dian)變(bian)壓(ya)器(qi)(qi)(qi)輸(shu)(shu)出電(dian)(dian)(dian)(dian)壓(ya)三(san)相不(bu)平衡,且不(bu)平衡率大(da)于(yu)3%時,變(bian)頻(pin)(pin)器(qi)(qi)(qi)輸(shu)(shu)入電(dian)(dian)(dian)(dian)流峰值很大(da),會造成導線過熱,則此時需(xu)加(jia)裝交流電(dian)(dian)(dian)(dian)抗(kang)器(qi)(qi)(qi)。嚴(yan)重時則需(xu)加(jia)裝直流電(dian)(dian)(dian)(dian)抗(kang)器(qi)(qi)(qi)。

(3)加裝(zhuang)無源濾波器

將無(wu)源(yuan)(yuan)濾波(bo)器安裝在變(bian)頻(pin)(pin)器的交流(liu)側,無(wu)源(yuan)(yuan)濾波(bo)器由L、C、R元件構成諧(xie)(xie)波(bo)共振回路(lu),當(dang)LC回路(lu)的諧(xie)(xie)波(bo)頻(pin)(pin)率和某一次高(gao)次諧(xie)(xie)波(bo)電流(liu)頻(pin)(pin)率相同(tong)時,即(ji)可阻止高(gao)次諧(xie)(xie)波(bo)流(liu)入電網。無(wu)源(yuan)(yuan)濾波(bo)器特點是投資少(shao)、頻(pin)(pin)率高(gao)、結構簡單(dan)、運(yun)行可靠及(ji)維護(hu)方便(bian)。無(wu)源(yuan)(yuan)濾波(bo)器缺點是濾波(bo)易受系統參(can)數的影(ying)響(xiang),對某些(xie)次諧(xie)(xie)波(bo)有放大的可能(neng)、耗費多、體積大。

(4)加(jia)裝有源濾波器(qi)

早在(zai)70年代(dai)初,日本學(xue)者就提(ti)出有源(yuan)濾波(bo)(bo)(bo)(bo)器的(de)(de)概念,由源(yuan)濾波(bo)(bo)(bo)(bo)器通過對電流中高(gao)次諧(xie)波(bo)(bo)(bo)(bo)進行檢(jian)測,根據(ju)檢(jian)測結果輸(shu)入與(yu)高(gao)次諧(xie)波(bo)(bo)(bo)(bo)成分(fen)具(ju)有相(xiang)反相(xiang)位電流,達(da)到實時(shi)補償諧(xie)波(bo)(bo)(bo)(bo)電流的(de)(de)目(mu)的(de)(de)。與(yu)無源(yuan)濾波(bo)(bo)(bo)(bo)器相(xiang)比具(ju)有高(gao)度可(ke)控性和快速響應性,有一機多能特(te)點(dian)。且可(ke)消除與(yu)系統阻抗發生(sheng)諧(xie)振危險。也可(ke)自動跟蹤補償變化的(de)(de)諧(xie)波(bo)(bo)(bo)(bo)。但(dan)存在(zai)容量大,價格高(gao)等特(te)點(dian)。

(5)加裝(zhuang)無功功率靜止(zhi)型(xing)無功補償裝(zhuang)置

對(dui)于大(da)型(xing)沖擊(ji)性(xing)負荷(he),可(ke)裝(zhuang)設無功功率的(de)靜止型(xing)無功補償裝(zhuang)置,以(yi)獲得補償負荷(he)快(kuai)速變(bian)動的(de)無功需求,改善功率因數(shu),濾除(chu)系統諧波,減少向(xiang)系統注入諧波電(dian)流(liu),穩定母線(xian)電(dian)壓,降低三相(xiang)電(dian)壓不(bu)平(ping)衡度(du)(du),提(ti)高(gao)供電(dian)系統承受諧波能(neng)力。而其(qi)中(zhong)以(yi)自飽(bao)和電(dian)抗型(xing)(SR型(xing))的(de)效果好,其(qi)電(dian)子元件(jian)少,可(ke)靠(kao)性(xing)高(gao),反應速度(du)(du)快(kuai),維(wei)護方便(bian)經濟,且我國一般(ban)變(bian)壓器(qi)廠均能(neng)制造。

(6)線路分開

因電(dian)源(yuan)系(xi)統(tong)內有阻抗,所(suo)以(yi)諧(xie)波(bo)負(fu)(fu)荷(he)電(dian)流將造成電(dian)壓(ya)波(bo)形的(de)諧(xie)波(bo)電(dian)壓(ya)畸形。把產(chan)生諧(xie)波(bo)的(de)負(fu)(fu)荷(he)的(de)供電(dian)線(xian)路(lu)和對諧(xie)波(bo)敏(min)感的(de)負(fu)(fu)荷(he)供電(dian)線(xian)路(lu)分開,線(xian)性(xing)(xing)負(fu)(fu)荷(he)和非線(xian)性(xing)(xing)負(fu)(fu)荷(he)從同(tong)一電(dian)源(yuan)接口(kou)點PCC開始(shi)由不同(tong)的(de)電(dian)路(lu)饋(kui)電(dian),使非線(xian)性(xing)(xing)負(fu)(fu)荷(he)產(chan)生的(de)畸變電(dian)壓(ya)不會(hui)傳(chuan)導(dao)到線(xian)性(xing)(xing)負(fu)(fu)荷(he)上(shang)去。

(7)電路(lu)的多重化、多元(yuan)化

逆變單(dan)元的(de)并聯多元化是采用2個(ge)或多個(ge)逆變單(dan)元并聯,通過波(bo)(bo)(bo)(bo)(bo)形移位(wei)疊加(jia),抵消(xiao)諧波(bo)(bo)(bo)(bo)(bo)分量;整流(liu)電路的(de)多重化是采用12脈(mo)波(bo)(bo)(bo)(bo)(bo)、18脈(mo)波(bo)(bo)(bo)(bo)(bo)、24脈(mo)波(bo)(bo)(bo)(bo)(bo)整流(liu),可降(jiang)低(di)諧波(bo)(bo)(bo)(bo)(bo)成(cheng)分;功(gong)率(lv)單(dan)元的(de)串聯多重化是采用多脈(mo)波(bo)(bo)(bo)(bo)(bo)(如30脈(mo)波(bo)(bo)(bo)(bo)(bo)的(de)串聯),功(gong)率(lv)單(dan)元多重化線路也可降(jiang)低(di)諧波(bo)(bo)(bo)(bo)(bo)成(cheng)分。此外還(huan)有新的(de)變頻調(diao)制方(fang)法,如電壓矢量的(de)變形調(diao)制。

(8)變頻(pin)器的控制方式的完善

隨著(zhu)電力電子(zi)技(ji)術(shu)、微電子(zi)技(ji)術(shu)、計算機(ji)網絡(luo)等高新(xin)技(ji)術(shu)發展,變(bian)頻(pin)(pin)器(qi)(qi)控(kong)制(zhi)方(fang)(fang)式有了以下發展:數字控(kong)制(zhi)變(bian)頻(pin)(pin)器(qi)(qi),變(bian)頻(pin)(pin)器(qi)(qi)數字化采用(yong)單(dan)片機(ji)MCS51或80C196MC等,輔助(zhu)以SLE4520或EPLD液晶顯(xian)示器(qi)(qi)等來(lai)實現更(geng)加完(wan)善的(de)(de)控(kong)制(zhi)性能;多(duo)種控(kong)制(zhi)方(fang)(fang)式結(jie)(jie)合,單(dan)一(yi)的(de)(de)控(kong)制(zhi)方(fang)(fang)式有著(zhu)各(ge)自的(de)(de)缺點,如果(guo)將(jiang)這些單(dan)一(yi)控(kong)制(zhi)方(fang)(fang)式結(jie)(jie)合起(qi)來(lai),可以取長補短,從(cong)而達(da)到降(jiang)低(di)諧波提升效率的(de)(de)功效。

(9)使用理想化的無諧波(bo)污染的綠色(se)變頻器

綠色(se)變(bian)頻器的品質標準是:輸(shu)(shu)入和輸(shu)(shu)出電流都(dou)是正(zheng)弦波,輸(shu)(shu)入功(gong)率(lv)因數可控(kong),帶任(ren)何負載使(shi)都(dou)能使(shi)功(gong)率(lv)因數為1,可獲(huo)得工頻上下任(ren)意(yi)可控(kong)的輸(shu)(shu)出功(gong)率(lv)。

綜(zong)上(shang)所述,可以(yi)了解變(bian)(bian)(bian)(bian)頻器(qi)(qi)(qi)以(yi)及(ji)(ji)變(bian)(bian)(bian)(bian)頻器(qi)(qi)(qi)諧(xie)波(bo)產生的(de)機理,變(bian)(bian)(bian)(bian)頻器(qi)(qi)(qi)諧(xie)波(bo)以(yi)及(ji)(ji)其危害性,以(yi)及(ji)(ji)采用變(bian)(bian)(bian)(bian)頻器(qi)(qi)(qi)隔離、接地或(huo)采用無源濾(lv)波(bo)器(qi)(qi)(qi)、有(you)源濾(lv)波(bo)器(qi)(qi)(qi)、加設無功(gong)補償裝置以(yi)及(ji)(ji)綠(lv)色變(bian)(bian)(bian)(bian)頻器(qi)(qi)(qi)等(deng)方法。

隨著電(dian)力電(dian)子(zi)技術(shu)以及微電(dian)子(zi)技術(shu)等技術(shu)的飛速發展(zhan),在治理諧波問題上(shang)將(jiang)會邁(mai)上(shang)一個新的臺(tai)階,將(jiang)變頻器產生的諧波控(kong)制在最小范圍之內以達到抑制電(dian)網污染,提高電(dian)能(neng)質量。

 

聲明

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(來源:網(wang)絡(luo),版(ban)權歸原作者)


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