一、什么是光伏逆變器

逆變器又(you)(you)稱電(dian)源調整(zheng)器(qi)(qi)(qi)(qi)，根(gen)據逆變(bian)器(qi)(qi)(qi)(qi)在(zai)光伏發電(dian)系統(tong)中的(de)用途(tu)可(ke)分為獨立型電(dian)源用和(he)并網用二種。根(gen)據波形調制方式又(you)(you)可(ke)分為方波逆變(bian)器(qi)(qi)(qi)(qi)、階梯波逆變(bian)器(qi)(qi)(qi)(qi)、正弦波逆變(bian)器(qi)(qi)(qi)(qi)和(he)組合式三相逆變(bian)器(qi)(qi)(qi)(qi)。對于(yu)用于(yu)并網系統(tong)的(de)逆變(bian)器(qi)(qi)(qi)(qi)，根(gen)據有(you)無變(bian)壓器(qi)(qi)(qi)(qi)又(you)(you)可(ke)分為變(bian)壓器(qi)(qi)(qi)(qi)型逆變(bian)器(qi)(qi)(qi)(qi)和(he)無變(bian)變(bian)壓器(qi)(qi)(qi)(qi)型逆變(bian)器(qi)(qi)(qi)(qi)。

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二、結構原理

逆變器是一種由半導體器件組成的電力調整裝置，主要用于把直流電力轉(zhuan)換成(cheng)(cheng)交(jiao)流(liu)(liu)電(dian)(dian)力。一般由升壓(ya)(ya)(ya)(ya)回(hui)路(lu)和(he)逆(ni)(ni)(ni)(ni)變(bian)(bian)橋式回(hui)路(lu)構(gou)成(cheng)(cheng)。升壓(ya)(ya)(ya)(ya)回(hui)路(lu)把太陽電(dian)(dian)池的直流(liu)(liu)電(dian)(dian)壓(ya)(ya)(ya)(ya)升壓(ya)(ya)(ya)(ya)到逆(ni)(ni)(ni)(ni)變(bian)(bian)器(qi)輸出控制(zhi)所需的直流(liu)(liu)電(dian)(dian)壓(ya)(ya)(ya)(ya)；逆(ni)(ni)(ni)(ni)變(bian)(bian)橋式回(hui)路(lu)則(ze)把升壓(ya)(ya)(ya)(ya)后的直流(liu)(liu)電(dian)(dian)壓(ya)(ya)(ya)(ya)等(deng)(deng)價地轉(zhuan)換成(cheng)(cheng)常(chang)用(yong)(yong)頻率的交(jiao)流(liu)(liu)電(dian)(dian)壓(ya)(ya)(ya)(ya)。逆(ni)(ni)(ni)(ni)變(bian)(bian)器(qi)主要由晶體管等(deng)(deng)開(kai)(kai)關(guan)(guan)(guan)元(yuan)(yuan)件(jian)(jian)(jian)構(gou)成(cheng)(cheng)，通(tong)過有規則(ze)地讓(rang)開(kai)(kai)關(guan)(guan)(guan)元(yuan)(yuan)件(jian)(jian)(jian)重復開(kai)(kai)-關(guan)(guan)(guan)（ON-OFF），使(shi)直流(liu)(liu)輸入變(bian)(bian)成(cheng)(cheng)交(jiao)流(liu)(liu)輸出。當(dang)然(ran)，這(zhe)樣單純地由開(kai)(kai)和(he)關(guan)(guan)(guan)回(hui)路(lu)產(chan)生(sheng)的逆(ni)(ni)(ni)(ni)變(bian)(bian)器(qi)輸出波(bo)(bo)(bo)(bo)形并不實用(yong)(yong)。一般需要采用(yong)(yong)高(gao)頻脈(mo)寬(kuan)調(diao)制(zhi)（SPWM），使(shi)靠(kao)近正(zheng)弦(xian)(xian)波(bo)(bo)(bo)(bo)兩端的電(dian)(dian)壓(ya)(ya)(ya)(ya)寬(kuan)度變(bian)(bian)狹，正(zheng)弦(xian)(xian)波(bo)(bo)(bo)(bo)中央的電(dian)(dian)壓(ya)(ya)(ya)(ya)寬(kuan)度變(bian)(bian)寬(kuan)，并在半周(zhou)期(qi)內始終讓(rang)開(kai)(kai)關(guan)(guan)(guan)元(yuan)(yuan)件(jian)(jian)(jian)按一定頻率朝一方向動作，這(zhe)樣形成(cheng)(cheng)一個脈(mo)沖(chong)波(bo)(bo)(bo)(bo)列（擬正(zheng)弦(xian)(xian)波(bo)(bo)(bo)(bo)）。然(ran)后讓(rang)脈(mo)沖(chong)波(bo)(bo)(bo)(bo)通(tong)過簡單的濾波(bo)(bo)(bo)(bo)器(qi)形成(cheng)(cheng)正(zheng)弦(xian)(xian)波(bo)(bo)(bo)(bo)。

三、逆變器的元器件構成

1、電流傳感器

對于(yu)電流(liu)傳(chuan)感(gan)(gan)器(qi)要求精(jing)度(du)高(gao)(gao)、響應時間快，而(er)且耐(nai)低(di)溫、高(gao)(gao)溫等環(huan)境(jing)要求，目前國(guo)內很多廠家都用開環(huan)電流(liu)傳(chuan)感(gan)(gan)器(qi)來取代閉環(huan)電流(liu)傳(chuan)感(gan)(gan)器(qi)，如(ru)：JCE1000-AXS、JCE1500-AXS、JCE2000-AXS等

2、電流互感器

一(yi)般采用BRS系列電(dian)流(liu)互感器，從幾百到幾千A不等，輸(shu)出信號一(yi)般采用0-5A為標準

3、電抗器

三、功能

1、自動運行和停機功能

早晨日出(chu)(chu)(chu)后，太陽(yang)輻(fu)射強度(du)逐漸增強，太陽(yang)電池的輸(shu)(shu)(shu)出(chu)(chu)(chu)也(ye)隨之增大，當達到逆(ni)變(bian)(bian)器(qi)工(gong)(gong)作所(suo)需的輸(shu)(shu)(shu)出(chu)(chu)(chu)功率(lv)后，逆(ni)變(bian)(bian)器(qi)即自動開始運(yun)行。進入運(yun)行后，逆(ni)變(bian)(bian)器(qi)便(bian)時時刻(ke)刻(ke)監視太陽(yang)電池組(zu)件的輸(shu)(shu)(shu)出(chu)(chu)(chu)，只要太陽(yang)電池組(zu)件的輸(shu)(shu)(shu)出(chu)(chu)(chu)功率(lv)大于逆(ni)變(bian)(bian)器(qi)工(gong)(gong)作所(suo)需的輸(shu)(shu)(shu)出(chu)(chu)(chu)功率(lv)，逆(ni)變(bian)(bian)器(qi)就持續運(yun)行；直到日落(luo)停(ting)機，即使陰雨天逆(ni)變(bian)(bian)器(qi)也(ye)能運(yun)行。當太陽(yang)電池組(zu)件輸(shu)(shu)(shu)出(chu)(chu)(chu)變(bian)(bian)小(xiao)，逆(ni)變(bian)(bian)器(qi)輸(shu)(shu)(shu)出(chu)(chu)(chu)接近0時，逆(ni)變(bian)(bian)器(qi)便(bian)形(xing)成待機狀態(tai)。

2、最大功率跟蹤控制功能

太陽能電(dian)池組(zu)件(jian)(jian)(jian)的(de)(de)輸出是隨(sui)太(tai)(tai)陽(yang)(yang)輻射強(qiang)度(du)(du)和太(tai)(tai)陽(yang)(yang)電(dian)池組(zu)件(jian)(jian)(jian)自(zi)身溫(wen)度(du)(du)（芯片溫(wen)度(du)(du)）而變化的(de)(de)。另外由于太(tai)(tai)陽(yang)(yang)電(dian)池組(zu)件(jian)(jian)(jian)具有電(dian)壓隨(sui)電(dian)流增大而下降的(de)(de)特性，因此(ci)存在(zai)能(neng)獲取最(zui)大功(gong)(gong)(gong)(gong)(gong)率的(de)(de)最(zui)佳工(gong)作點(dian)。太(tai)(tai)陽(yang)(yang)輻射強(qiang)度(du)(du)是變化著的(de)(de)，顯然最(zui)佳工(gong)作點(dian)也(ye)是在(zai)變化的(de)(de)。相對于這(zhe)些變化，始終讓太(tai)(tai)陽(yang)(yang)電(dian)池組(zu)件(jian)(jian)(jian)的(de)(de)工(gong)作點(dian)處于最(zui)大功(gong)(gong)(gong)(gong)(gong)率點(dian)，系(xi)統始終從太(tai)(tai)陽(yang)(yang)電(dian)池組(zu)件(jian)(jian)(jian)獲取最(zui)大功(gong)(gong)(gong)(gong)(gong)率輸出，這(zhe)種控(kong)制(zhi)就是最(zui)大功(gong)(gong)(gong)(gong)(gong)率跟蹤控(kong)制(zhi)。太(tai)(tai)陽(yang)(yang)能(neng)發電(dian)系(xi)統用的(de)(de)逆變器的(de)(de)最(zui)大特點(dian)就是包括(kuo)了最(zui)大功(gong)(gong)(gong)(gong)(gong)率點(dian)跟蹤（MPPT）這(zhe)一功(gong)(gong)(gong)(gong)(gong)能(neng)。

四、選購步驟及方法

1、功率

一般根(gen)據系統的(de)要求配(pei)(pei)置對應(ying)功(gong)率段的(de)逆(ni)(ni)變器，選型的(de)逆(ni)(ni)變器的(de)功(gong)率應(ying)該與(yu)(yu)太陽能(neng)電池方陣(zhen)的(de)最大功(gong)率匹配(pei)(pei)，一般選取光伏逆(ni)(ni)變器的(de)額定輸(shu)出功(gong)率與(yu)(yu)輸(shu)入總功(gong)率相近左(zuo)右(you)，這(zhe)樣可(ke)以節約成本。

2、關鍵技術指標

1）選擇合適(shi)的輸入輸出電壓范圍，確保產品的最(zui)優組合。

2）逆變器的歐洲效(xiao)率(lv)：它的高(gao)低將直接影響到光(guang)伏發(fa)電系統(tong)的設計成本(ben)與發(fa)電效(xiao)率(lv)。

3）太(tai)陽(yang)電池方陣最大功(gong)率(lv)跟蹤功(gong)能（MPPT）及其效率(lv)。

4）應(ying)注意(yi)所(suo)選用的逆變(bian)器應(ying)有基本的保(bao)(bao)護(hu)(hu)功(gong)能(neng)，如過流/短路保(bao)(bao)護(hu)(hu)、過功(gong)率(lv)保(bao)(bao)護(hu)(hu)，過溫保(bao)(bao)護(hu)(hu)，防雷保(bao)(bao)護(hu)(hu)、孤島保(bao)(bao)護(hu)(hu)等功(gong)能(neng)。

5）逆變器(qi)輸出電(dian)流(liu)波形畸(ji)變率(lv)（THD%）要低于4%。

3、認證標準

作為(wei)光伏電(dian)站的核心設備，為(wei)保證(zheng)電(dian)站的穩定、可靠、持續運(yun)行，并(bing)網(wang)逆變器(qi)必須(xu)有很高的可靠性。它應具有銷售目(mu)的地的安規認證(zheng)，電(dian)磁兼容認證(zheng)，及各國并(bing)網(wang)認證(zheng)：（以(yi)歐洲為(wei)例）

安規：EN62109-1，EN62109-2

電磁兼容:EN61000-6-1,EN61000-6-2,EN61000-6-3,EN61000-6-4

并網認證(zheng):VDE0126-1-1(德國(guo))

4、品牌與服務

建(jian)議購買目前市場(chang)上口碑(bei)不錯(cuo)的(de)品牌(pai)，因為一般(ban)品牌(pai)形象好的(de)公司(si)，通(tong)常會在技術，以及維修服務(wu)上有較大(da)的(de)投(tou)資，能滿(man)足對客戶的(de)承諾。