一、什么是光伏逆變器
逆變器又稱電源(yuan)(yuan)調整器(qi)(qi),根據逆(ni)變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)在光(guang)伏發(fa)電系(xi)統(tong)(tong)中的(de)用(yong)途(tu)可(ke)分為(wei)獨立型電源(yuan)(yuan)用(yong)和(he)并網用(yong)二種。根據波(bo)形調制(zhi)方式(shi)(shi)又可(ke)分為(wei)方波(bo)逆(ni)變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)、階梯波(bo)逆(ni)變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)、正弦波(bo)逆(ni)變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)和(he)組合式(shi)(shi)三相逆(ni)變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)。對于用(yong)于并網系(xi)統(tong)(tong)的(de)逆(ni)變(bian)(bian)(bian)(bian)(bian)器(qi)(qi),根據有無(wu)變(bian)(bian)(bian)(bian)(bian)壓器(qi)(qi)又可(ke)分為(wei)變(bian)(bian)(bian)(bian)(bian)壓器(qi)(qi)型逆(ni)變(bian)(bian)(bian)(bian)(bian)器(qi)(qi)和(he)無(wu)變(bian)(bian)(bian)(bian)(bian)變(bian)(bian)(bian)(bian)(bian)壓器(qi)(qi)型逆(ni)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(huan)(huan)成交流(liu)(liu)電(dian)(dian)力。一般(ban)由升(sheng)壓(ya)(ya)(ya)回(hui)路(lu)和逆(ni)(ni)變(bian)(bian)橋式(shi)回(hui)路(lu)構成。升(sheng)壓(ya)(ya)(ya)回(hui)路(lu)把太陽電(dian)(dian)池的(de)(de)(de)直(zhi)(zhi)流(liu)(liu)電(dian)(dian)壓(ya)(ya)(ya)升(sheng)壓(ya)(ya)(ya)到逆(ni)(ni)變(bian)(bian)器(qi)輸(shu)出控制(zhi)所需的(de)(de)(de)直(zhi)(zhi)流(liu)(liu)電(dian)(dian)壓(ya)(ya)(ya);逆(ni)(ni)變(bian)(bian)橋式(shi)回(hui)路(lu)則把升(sheng)壓(ya)(ya)(ya)后(hou)的(de)(de)(de)直(zhi)(zhi)流(liu)(liu)電(dian)(dian)壓(ya)(ya)(ya)等(deng)價地轉換(huan)(huan)成常用(yong)頻率的(de)(de)(de)交流(liu)(liu)電(dian)(dian)壓(ya)(ya)(ya)。逆(ni)(ni)變(bian)(bian)器(qi)主要由晶體(ti)管(guan)等(deng)開(kai)(kai)關元件(jian)(jian)構成,通(tong)過有規則地讓(rang)開(kai)(kai)關元件(jian)(jian)重復開(kai)(kai)-關(ON-OFF),使(shi)直(zhi)(zhi)流(liu)(liu)輸(shu)入變(bian)(bian)成交流(liu)(liu)輸(shu)出。當然(ran),這樣單純(chun)地由開(kai)(kai)和關回(hui)路(lu)產生的(de)(de)(de)逆(ni)(ni)變(bian)(bian)器(qi)輸(shu)出波(bo)(bo)形并(bing)(bing)不實用(yong)。一般(ban)需要采用(yong)高頻脈寬(kuan)(kuan)調制(zhi)(SPWM),使(shi)靠(kao)近正(zheng)弦(xian)波(bo)(bo)兩端(duan)的(de)(de)(de)電(dian)(dian)壓(ya)(ya)(ya)寬(kuan)(kuan)度變(bian)(bian)狹(xia),正(zheng)弦(xian)波(bo)(bo)中(zhong)央(yang)的(de)(de)(de)電(dian)(dian)壓(ya)(ya)(ya)寬(kuan)(kuan)度變(bian)(bian)寬(kuan)(kuan),并(bing)(bing)在半(ban)周期(qi)內始終讓(rang)開(kai)(kai)關元件(jian)(jian)按一定(ding)頻率朝一方(fang)向(xiang)動作(zuo),這樣形成一個脈沖波(bo)(bo)列(擬正(zheng)弦(xian)波(bo)(bo))。然(ran)后(hou)讓(rang)脈沖波(bo)(bo)通(tong)過簡(jian)單的(de)(de)(de)濾(lv)波(bo)(bo)器(qi)形成正(zheng)弦(xian)波(bo)(bo)。
三、逆變器的元器件構成
1、電流傳感器
對于(yu)電流傳(chuan)感器(qi)要(yao)求(qiu)精度高(gao)(gao)、響應(ying)時間快,而且(qie)耐低溫、高(gao)(gao)溫等(deng)環境要(yao)求(qiu),目(mu)前(qian)國內很多廠家都用開(kai)環電流傳(chuan)感器(qi)來取代閉環電流傳(chuan)感器(qi),如(ru):JCE1000-AXS、JCE1500-AXS、JCE2000-AXS等(deng)
2、電流互感器
一(yi)般(ban)采(cai)用(yong)BRS系(xi)列電流互感器,從幾(ji)百到幾(ji)千A不等,輸出信號(hao)一(yi)般(ban)采(cai)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(chen)日出后,太(tai)(tai)陽(yang)輻射(she)強(qiang)(qiang)度逐漸(jian)增(zeng)強(qiang)(qiang),太(tai)(tai)陽(yang)電池的輸(shu)(shu)出也(ye)隨之增(zeng)大,當達到逆(ni)(ni)變(bian)(bian)器(qi)工作(zuo)所需的輸(shu)(shu)出功(gong)率(lv)后,逆(ni)(ni)變(bian)(bian)器(qi)即自動開始運(yun)行。進入運(yun)行后,逆(ni)(ni)變(bian)(bian)器(qi)便(bian)時(shi)時(shi)刻刻監視太(tai)(tai)陽(yang)電池組(zu)件(jian)(jian)的輸(shu)(shu)出,只要太(tai)(tai)陽(yang)電池組(zu)件(jian)(jian)的輸(shu)(shu)出功(gong)率(lv)大于逆(ni)(ni)變(bian)(bian)器(qi)工作(zuo)所需的輸(shu)(shu)出功(gong)率(lv),逆(ni)(ni)變(bian)(bian)器(qi)就持續運(yun)行;直到日落停機(ji),即使陰(yin)雨(yu)天逆(ni)(ni)變(bian)(bian)器(qi)也(ye)能運(yun)行。當太(tai)(tai)陽(yang)電池組(zu)件(jian)(jian)輸(shu)(shu)出變(bian)(bian)小(xiao),逆(ni)(ni)變(bian)(bian)器(qi)輸(shu)(shu)出接近(jin)0時(shi),逆(ni)(ni)變(bian)(bian)器(qi)便(bian)形成(cheng)待(dai)機(ji)狀態。
2、最大功率跟蹤控制功能
太陽能電池組(zu)件(jian)(jian)的(de)(de)輸出是(shi)隨(sui)太陽(yang)(yang)輻(fu)射強度(du)和太陽(yang)(yang)電池組(zu)件(jian)(jian)自身溫度(du)(芯片(pian)溫度(du))而變(bian)(bian)化的(de)(de)。另外(wai)由于(yu)太陽(yang)(yang)電池組(zu)件(jian)(jian)具有電壓隨(sui)電流增大(da)(da)(da)而下降(jiang)的(de)(de)特(te)性,因(yin)此存在(zai)能(neng)獲(huo)取(qu)最大(da)(da)(da)功(gong)(gong)率(lv)(lv)(lv)的(de)(de)最佳工作點。太陽(yang)(yang)輻(fu)射強度(du)是(shi)變(bian)(bian)化著的(de)(de),顯然最佳工作點也是(shi)在(zai)變(bian)(bian)化的(de)(de)。相對于(yu)這些(xie)變(bian)(bian)化,始終讓太陽(yang)(yang)電池組(zu)件(jian)(jian)的(de)(de)工作點處于(yu)最大(da)(da)(da)功(gong)(gong)率(lv)(lv)(lv)點,系(xi)統(tong)始終從太陽(yang)(yang)電池組(zu)件(jian)(jian)獲(huo)取(qu)最大(da)(da)(da)功(gong)(gong)率(lv)(lv)(lv)輸出,這種(zhong)控制就(jiu)是(shi)最大(da)(da)(da)功(gong)(gong)率(lv)(lv)(lv)跟(gen)蹤(zong)(zong)控制。太陽(yang)(yang)能(neng)發電系(xi)統(tong)用的(de)(de)逆(ni)變(bian)(bian)器(qi)的(de)(de)最大(da)(da)(da)特(te)點就(jiu)是(shi)包(bao)括了最大(da)(da)(da)功(gong)(gong)率(lv)(lv)(lv)點跟(gen)蹤(zong)(zong)(MPPT)這一功(gong)(gong)能(neng)。
四、選購步驟及方法
1、功率
一(yi)般(ban)(ban)根(gen)據系統的要求(qiu)配(pei)置對應功(gong)率(lv)(lv)段的逆(ni)變器(qi),選型的逆(ni)變器(qi)的功(gong)率(lv)(lv)應該與太(tai)陽(yang)能電池方陣的最大功(gong)率(lv)(lv)匹(pi)配(pei),一(yi)般(ban)(ban)選取光伏逆(ni)變器(qi)的額定輸出功(gong)率(lv)(lv)與輸入總(zong)功(gong)率(lv)(lv)相近左右(you),這樣可以節約成本。
2、關鍵技術指標
1)選擇合適的輸入輸出電壓范圍,確保產品的最(zui)優(you)組合。
2)逆變器的歐洲效率:它的高低將直接影(ying)響(xiang)到光伏發電(dian)系統的設計成本與發電(dian)效率。
3)太陽(yang)電池方陣最大功率(lv)跟蹤功能(MPPT)及(ji)其效率(lv)。
4)應注(zhu)意所選用的(de)逆變(bian)器應有(you)基本的(de)保(bao)(bao)(bao)護(hu)功能(neng),如過(guo)流/短(duan)路保(bao)(bao)(bao)護(hu)、過(guo)功率保(bao)(bao)(bao)護(hu),過(guo)溫(wen)保(bao)(bao)(bao)護(hu),防雷保(bao)(bao)(bao)護(hu)、孤島保(bao)(bao)(bao)護(hu)等(deng)功能(neng)。
5)逆變器輸出電流波形(xing)畸(ji)變率(THD%)要低(di)于4%。
3、認證標準
作為(wei)光伏電站的(de)核心設備(bei),為(wei)保證(zheng)電站的(de)穩定(ding)、可靠、持續(xu)運行,并網逆變器必(bi)須有(you)很高的(de)可靠性(xing)。它應具有(you)銷(xiao)售目的(de)地(di)的(de)安(an)規認證(zheng),電磁兼容認證(zheng),及各國并網認證(zheng):(以歐洲為(wei)例)
安(an)規:EN62109-1,EN62109-2
電磁兼容:EN61000-6-1,EN61000-6-2,EN61000-6-3,EN61000-6-4
并(bing)網認證:VDE0126-1-1(德國)
4、品牌與服務
建議購買目前市場上口碑不(bu)錯的(de)品牌,因(yin)為(wei)一般品牌形象(xiang)好的(de)公司,通常會在技術,以(yi)及(ji)維修服務上有較大的(de)投資(zi),能滿足對客戶的(de)承諾。