一、什么是光伏逆變器
逆變器又稱電(dian)源調(diao)整器(qi)(qi),根(gen)(gen)據(ju)(ju)逆變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)在(zai)光伏發電(dian)系統(tong)中的用途可(ke)分(fen)為獨立型電(dian)源用和(he)并網用二種。根(gen)(gen)據(ju)(ju)波形調(diao)制方(fang)(fang)式又可(ke)分(fen)為方(fang)(fang)波逆變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)、階梯波逆變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)、正弦波逆變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)和(he)組合式三相(xiang)逆變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)。對(dui)于(yu)用于(yu)并網系統(tong)的逆變(bian)(bian)(bian)(bian)(bian)器(qi)(qi),根(gen)(gen)據(ju)(ju)有無變(bian)(bian)(bian)(bian)(bian)壓器(qi)(qi)又可(ke)分(fen)為變(bian)(bian)(bian)(bian)(bian)壓器(qi)(qi)型逆變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)和(he)無變(bian)(bian)(bian)(bian)(bian)變(bian)(bian)(bian)(bian)(bian)壓器(qi)(qi)型逆變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)。
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換成(cheng)(cheng)(cheng)交(jiao)流(liu)電(dian)力(li)。一(yi)般(ban)由(you)升(sheng)壓(ya)(ya)回(hui)路(lu)(lu)和逆(ni)變(bian)橋式(shi)回(hui)路(lu)(lu)構成(cheng)(cheng)(cheng)。升(sheng)壓(ya)(ya)回(hui)路(lu)(lu)把(ba)太陽(yang)電(dian)池的(de)直(zhi)(zhi)流(liu)電(dian)壓(ya)(ya)升(sheng)壓(ya)(ya)到逆(ni)變(bian)器(qi)輸(shu)出(chu)控制所(suo)需(xu)(xu)的(de)直(zhi)(zhi)流(liu)電(dian)壓(ya)(ya);逆(ni)變(bian)橋式(shi)回(hui)路(lu)(lu)則把(ba)升(sheng)壓(ya)(ya)后的(de)直(zhi)(zhi)流(liu)電(dian)壓(ya)(ya)等(deng)(deng)價地轉換成(cheng)(cheng)(cheng)常用(yong)頻(pin)率(lv)的(de)交(jiao)流(liu)電(dian)壓(ya)(ya)。逆(ni)變(bian)器(qi)主要(yao)由(you)晶體管等(deng)(deng)開關(guan)元件構成(cheng)(cheng)(cheng),通(tong)過(guo)有規(gui)則地讓開關(guan)元件重復開-關(guan)(ON-OFF),使直(zhi)(zhi)流(liu)輸(shu)入變(bian)成(cheng)(cheng)(cheng)交(jiao)流(liu)輸(shu)出(chu)。當然,這樣單(dan)純(chun)地由(you)開和關(guan)回(hui)路(lu)(lu)產(chan)生(sheng)的(de)逆(ni)變(bian)器(qi)輸(shu)出(chu)波(bo)(bo)形并不實用(yong)。一(yi)般(ban)需(xu)(xu)要(yao)采用(yong)高頻(pin)脈(mo)寬調制(SPWM),使靠近正(zheng)(zheng)弦(xian)(xian)波(bo)(bo)兩端(duan)的(de)電(dian)壓(ya)(ya)寬度變(bian)狹,正(zheng)(zheng)弦(xian)(xian)波(bo)(bo)中央的(de)電(dian)壓(ya)(ya)寬度變(bian)寬,并在(zai)半周期內始(shi)終(zhong)讓開關(guan)元件按一(yi)定頻(pin)率(lv)朝一(yi)方向動(dong)作(zuo),這樣形成(cheng)(cheng)(cheng)一(yi)個脈(mo)沖(chong)波(bo)(bo)列(擬(ni)正(zheng)(zheng)弦(xian)(xian)波(bo)(bo))。然后讓脈(mo)沖(chong)波(bo)(bo)通(tong)過(guo)簡(jian)單(dan)的(de)濾波(bo)(bo)器(qi)形成(cheng)(cheng)(cheng)正(zheng)(zheng)弦(xian)(xian)波(bo)(bo)。
三、逆變器的元器件構成
1、電流傳感器
對于(yu)電(dian)流傳(chuan)(chuan)感(gan)器(qi)要求精度(du)高(gao)、響應時(shi)間快,而(er)且耐低溫、高(gao)溫等環境要求,目前國內(nei)很多廠家(jia)都用開(kai)環電(dian)流傳(chuan)(chuan)感(gan)器(qi)來取代閉(bi)環電(dian)流傳(chuan)(chuan)感(gan)器(qi),如:JCE1000-AXS、JCE1500-AXS、JCE2000-AXS等
2、電流互感器
一(yi)般采用(yong)BRS系列電流互(hu)感器,從(cong)幾百(bai)到幾千A不等,輸出信號一(yi)般采用(yong)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)后,太陽(yang)輻射強度(du)逐(zhu)漸增(zeng)強,太陽(yang)電池(chi)(chi)的(de)(de)(de)輸出(chu)(chu)也(ye)隨之增(zeng)大(da),當達到逆(ni)(ni)變(bian)器(qi)(qi)工(gong)作所(suo)需(xu)的(de)(de)(de)輸出(chu)(chu)功(gong)率(lv)后,逆(ni)(ni)變(bian)器(qi)(qi)即(ji)自動開始運(yun)(yun)行(xing)(xing)(xing)。進入運(yun)(yun)行(xing)(xing)(xing)后,逆(ni)(ni)變(bian)器(qi)(qi)便(bian)(bian)時時刻刻監視(shi)太陽(yang)電池(chi)(chi)組(zu)件的(de)(de)(de)輸出(chu)(chu),只要太陽(yang)電池(chi)(chi)組(zu)件的(de)(de)(de)輸出(chu)(chu)功(gong)率(lv)大(da)于(yu)逆(ni)(ni)變(bian)器(qi)(qi)工(gong)作所(suo)需(xu)的(de)(de)(de)輸出(chu)(chu)功(gong)率(lv),逆(ni)(ni)變(bian)器(qi)(qi)就(jiu)持續(xu)運(yun)(yun)行(xing)(xing)(xing);直到日落停機,即(ji)使陰雨(yu)天逆(ni)(ni)變(bian)器(qi)(qi)也(ye)能(neng)運(yun)(yun)行(xing)(xing)(xing)。當太陽(yang)電池(chi)(chi)組(zu)件輸出(chu)(chu)變(bian)小(xiao),逆(ni)(ni)變(bian)器(qi)(qi)輸出(chu)(chu)接近0時,逆(ni)(ni)變(bian)器(qi)(qi)便(bian)(bian)形成(cheng)待機狀態。
2、最大功率跟蹤控制功能
太陽能電(dian)(dian)池(chi)組件(jian)的(de)(de)(de)輸(shu)出(chu)(chu)是(shi)隨太陽(yang)(yang)(yang)輻射強度和(he)太陽(yang)(yang)(yang)電(dian)(dian)池(chi)組件(jian)自(zi)身溫度(芯片溫度)而變(bian)化(hua)的(de)(de)(de)。另外由(you)于太陽(yang)(yang)(yang)電(dian)(dian)池(chi)組件(jian)具有電(dian)(dian)壓隨電(dian)(dian)流增大(da)而下降的(de)(de)(de)特(te)性,因此存在能獲(huo)取最(zui)(zui)(zui)大(da)功率的(de)(de)(de)最(zui)(zui)(zui)佳工作點(dian)。太陽(yang)(yang)(yang)輻射強度是(shi)變(bian)化(hua)著(zhu)的(de)(de)(de),顯然最(zui)(zui)(zui)佳工作點(dian)也是(shi)在變(bian)化(hua)的(de)(de)(de)。相對于這些變(bian)化(hua),始終讓太陽(yang)(yang)(yang)電(dian)(dian)池(chi)組件(jian)的(de)(de)(de)工作點(dian)處于最(zui)(zui)(zui)大(da)功率點(dian),系(xi)統始終從太陽(yang)(yang)(yang)電(dian)(dian)池(chi)組件(jian)獲(huo)取最(zui)(zui)(zui)大(da)功率輸(shu)出(chu)(chu),這種(zhong)控(kong)(kong)制(zhi)就是(shi)最(zui)(zui)(zui)大(da)功率跟(gen)蹤控(kong)(kong)制(zhi)。太陽(yang)(yang)(yang)能發電(dian)(dian)系(xi)統用的(de)(de)(de)逆變(bian)器的(de)(de)(de)最(zui)(zui)(zui)大(da)特(te)點(dian)就是(shi)包括了最(zui)(zui)(zui)大(da)功率點(dian)跟(gen)蹤(MPPT)這一功能。
四、選購步驟及方法
1、功率
一般(ban)根據系統的(de)(de)要求配置對(dui)應功率(lv)段的(de)(de)逆變器(qi)(qi),選型(xing)的(de)(de)逆變器(qi)(qi)的(de)(de)功率(lv)應該與太陽能(neng)電池方陣(zhen)的(de)(de)最大功率(lv)匹配,一般(ban)選取光伏逆變器(qi)(qi)的(de)(de)額定(ding)輸出功率(lv)與輸入總功率(lv)相近左右,這樣可(ke)以節約成本。
2、關鍵技術指標
1)選擇(ze)合適的(de)輸(shu)(shu)入輸(shu)(shu)出電壓范圍,確保產品的(de)最優組合。
2)逆變器的歐洲效(xiao)率(lv):它的高(gao)低將直接影(ying)響到光伏發(fa)電系統的設(she)計成本與發(fa)電效(xiao)率(lv)。
3)太陽電池方(fang)陣最(zui)大功率跟蹤功能(MPPT)及其效率。
4)應注(zhu)意所選用(yong)的(de)逆變器應有(you)基(ji)本的(de)保護(hu)(hu)功(gong)(gong)能,如(ru)過(guo)流(liu)/短路(lu)保護(hu)(hu)、過(guo)功(gong)(gong)率保護(hu)(hu),過(guo)溫保護(hu)(hu),防雷保護(hu)(hu)、孤島保護(hu)(hu)等功(gong)(gong)能。
5)逆變器輸(shu)出電流波(bo)形(xing)畸變率(THD%)要低于4%。
3、認證標準
作(zuo)為光(guang)伏電(dian)站的(de)核心設(she)備,為保證(zheng)電(dian)站的(de)穩定、可(ke)靠、持續運行,并網(wang)逆變器必(bi)須有很高的(de)可(ke)靠性。它應(ying)具有銷售目的(de)地的(de)安(an)規認(ren)證(zheng),電(dian)磁兼容認(ren)證(zheng),及各國并網(wang)認(ren)證(zheng):(以歐洲為例)
安規:EN62109-1,EN62109-2
電(dian)磁兼容:EN61000-6-1,EN61000-6-2,EN61000-6-3,EN61000-6-4
并網認(ren)證:VDE0126-1-1(德國)
4、品牌與服務
建議購買目前市場(chang)上口碑(bei)不(bu)錯的品牌,因為(wei)一(yi)般品牌形(xing)象好的公司,通常會(hui)在技(ji)術,以及(ji)維修服務上有較大的投資,能滿足對(dui)客戶的承諾(nuo)。