隨著我國電(dian)力市場(chang)化改革(ge)的(de)(de)不斷推進(jin)(jin),對電(dian)力工業(ye)(ye)也帶(dai)來了(le)一定程度的(de)(de)影(ying)響(xiang),進(jin)(jin)而致使電(dian)力行業(ye)(ye)發生了(le)巨大的(de)(de)變化。但(dan)同時也使電(dian)力企業(ye)(ye)的(de)(de)發展出現了(le)一系列問題(ti),對電(dian)力規(gui)劃的(de)(de)發展起(qi)到了(le)嚴重的(de)(de)不利影(ying)響(xiang)。基于此,本(ben)文針對電(dian)力市場(chang)化改革(ge)對電(dian)力規(gui)劃的(de)(de)影(ying)響(xiang)進(jin)(jin)行了(le)探(tan)討,以(yi)供(gong)參(can)考。
一、電力規劃的主要內容分析
通常(chang)情況下,電(dian)(dian)(dian)(dian)力(li)(li)企(qi)業在(zai)發展(zhan)過程中總會遇到(dao)一些(xie)因(yin)素(su)帶來的(de)(de)(de)影響(xiang)。因(yin)此在(zai)展(zhan)開電(dian)(dian)(dian)(dian)力(li)(li)規(gui)劃(hua)之前(qian),相關(guan)電(dian)(dian)(dian)(dian)力(li)(li)企(qi)業就應充(chong)分考慮到(dao)這(zhe)些(xie)因(yin)素(su)可(ke)能帶來的(de)(de)(de)影響(xiang)和破(po)壞(huai),之后嚴(yan)格(ge)按(an)照電(dian)(dian)(dian)(dian)網(wang)的(de)(de)(de)實際需要(yao)采取先進的(de)(de)(de)科(ke)學技術,保(bao)證電(dian)(dian)(dian)(dian)力(li)(li)規(gui)劃(hua)方(fang)(fang)案(an)具(ju)有科(ke)學合(he)理(li)(li)(li)化特點,并(bing)且電(dian)(dian)(dian)(dian)力(li)(li)規(gui)劃(hua)的(de)(de)(de)相應資金投入(ru)也要(yao)適當增加,繼而(er)促(cu)使電(dian)(dian)(dian)(dian)力(li)(li)規(gui)劃(hua)工(gong)作(zuo)(zuo)能夠順利展(zhan)開。而(er)電(dian)(dian)(dian)(dian)網(wang)在(zai)電(dian)(dian)(dian)(dian)力(li)(li)規(gui)劃(hua)中所起到(dao)的(de)(de)(de)作(zuo)(zuo)用主要(yao)包括以(yi)下幾(ji)種(zhong)形式:①在(zai)對(dui)電(dian)(dian)(dian)(dian)力(li)(li)規(gui)劃(hua)的(de)(de)(de)網(wang)架結(jie)構(gou)展(zhan)開優化措施時(shi),工(gong)作(zuo)(zuo)人(ren)員要(yao)嚴(yan)格(ge)按(an)照電(dian)(dian)(dian)(dian)容和負(fu)荷(he)的(de)(de)(de)分布情況有效落實,然(ran)后對(dui)電(dian)(dian)(dian)(dian)力(li)(li)規(gui)劃(hua)的(de)(de)(de)具(ju)體(ti)流程進行(xing)明確(que);②電(dian)(dian)(dian)(dian)力(li)(li)規(gui)劃(hua)的(de)(de)(de)相關(guan)工(gong)作(zuo)(zuo)人(ren)員還(huan)可(ke)以(yi)以(yi)實際規(gui)劃(hua)要(yao)求為基(ji)礎(chu)(chu),制定合(he)理(li)(li)(li)的(de)(de)(de)規(gui)劃(hua)方(fang)(fang)案(an)和標準,進而(er)保(bao)證電(dian)(dian)(dian)(dian)力(li)(li)規(gui)劃(hua)能實現經濟效益和社會效益的(de)(de)(de)最大化;③電(dian)(dian)(dian)(dian)力(li)(li)規(gui)劃(hua)人(ren)員在(zai)具(ju)體(ti)規(gui)劃(hua)之前(qian)要(yao)想充(chong)分了解負(fu)荷(he)估摸方(fang)(fang)面的(de)(de)(de)內容,并(bing)在(zai)此基(ji)礎(chu)(chu)上保(bao)證電(dian)(dian)(dian)(dian)力(li)(li)電(dian)(dian)(dian)(dian)量的(de)(de)(de)平(ping)衡(heng)運行(xing),從而(er)迅速明確(que)變(bian)電(dian)(dian)(dian)(dian)站的(de)(de)(de)地理(li)(li)(li)位置。
二、電力市場化改革背景下電力規劃的流程分析
1.提前做好規劃方案
一(yi)般在(zai)電(dian)(dian)力規劃(hua)工作(zuo)完成之后(hou)(hou),就會投入具(ju)體使(shi)用環(huan)節,而(er)電(dian)(dian)力企業的相關(guan)工作(zuo)人員就要根據電(dian)(dian)網的實(shi)際運(yun)行狀(zhuang)態來(lai)判斷(duan)其(qi)是否存(cun)在(zai)問題,并且對一(yi)些可能存(cun)在(zai)的安全隱(yin)患(huan)及(ji)時(shi)做好(hao)預防工作(zuo),進而(er)為后(hou)(hou)期工作(zuo)的順利展開奠定(ding)基礎。同時(shi),電(dian)(dian)力規劃(hua)中的步驟具(ju)體就是在(zai)計(ji)劃(hua)制定(ding)之后(hou)(hou)先交由上級部門進行檢查審核,在(zai)其(qi)認可通過之后(hou)(hou)方可按照上述規范標準有效落實(shi),這樣一(yi)來(lai)不但能使(shi)其(qi)規范充分(fen)滿足實(shi)際要求(qiu),還能保(bao)證后(hou)(hou)期工作(zuo)的順利進行。
2.針對電壓等級的選擇要保證科學合理
通(tong)常(chang)在對電(dian)(dian)力規(gui)劃安(an)全性進行(xing)(xing)(xing)考(kao)慮時(shi),最(zui)重(zhong)(zhong)要(yao)(yao)的(de)(de)一部分就是(shi)電(dian)(dian)壓(ya)(ya)等(deng)級(ji)的(de)(de)選(xuan)(xuan)(xuan)擇(ze),其將(jiang)直接(jie)關系(xi)到電(dian)(dian)網(wang)(wang)是(shi)否能夠穩定安(an)全的(de)(de)運行(xing)(xing)(xing),一旦電(dian)(dian)壓(ya)(ya)等(deng)級(ji)的(de)(de)選(xuan)(xuan)(xuan)擇(ze)存在過(guo)高或過(guo)低等(deng)情況,就會導(dao)致(zhi)線路由于負荷較大滿(man)足(zu)不了電(dian)(dian)網(wang)(wang)的(de)(de)標(biao)準要(yao)(yao)求(qiu),嚴重(zhong)(zhong)時(shi)甚至還會出現(xian)火災現(xian)象(xiang)。因此(ci)在對電(dian)(dian)壓(ya)(ya)等(deng)級(ji)進行(xing)(xing)(xing)選(xuan)(xuan)(xuan)擇(ze)時(shi),一定要(yao)(yao)極其慎重(zhong)(zhong),嚴格以電(dian)(dian)網(wang)(wang)實(shi)際(ji)需(xu)要(yao)(yao)為(wei)基礎展開合(he)理的(de)(de)選(xuan)(xuan)(xuan)擇(ze)。例如:在電(dian)(dian)力規(gui)劃中(zhong)通(tong)常(chang)可以將(jiang)電(dian)(dian)壓(ya)(ya)等(deng)級(ji)分為(wei)500kV、330kV、220kV及110kV等(deng),因此(ci)在進行(xing)(xing)(xing)電(dian)(dian)壓(ya)(ya)等(deng)級(ji)的(de)(de)選(xuan)(xuan)(xuan)擇(ze)一定要(yao)(yao)根據城(cheng)市與(yu)郊區等(deng)級(ji)之(zhi)間(jian)的(de)(de)區別進行(xing)(xing)(xing)針(zhen)對性的(de)(de)選(xuan)(xuan)(xuan)擇(ze)。尤其需(xu)要(yao)(yao)注(zhu)意(yi)的(de)(de)一點(dian)就是(shi)為(wei)了避(bi)免出現(xian)重(zhong)(zhong)復(fu)降壓(ya)(ya)的(de)(de)現(xian)象(xiang),相關工作人員應盡量選(xuan)(xuan)(xuan)擇(ze)合(he)適的(de)(de)中(zhong)電(dian)(dian)壓(ya)(ya)和(he)高電(dian)(dian)壓(ya)(ya)之(zhi)間(jian)的(de)(de)節(jie)點(dian),進而充分滿(man)足(zu)電(dian)(dian)網(wang)(wang)運行(xing)(xing)(xing)的(de)(de)實(shi)際(ji)需(xu)求(qiu)。
3.充分發揮電網負荷的轉移能力
若(ruo)想最大(da)限(xian)度(du)實現電(dian)(dian)(dian)網(wang)(wang)運行(xing)(xing)的(de)(de)(de)安(an)全可靠性,就(jiu)(jiu)要(yao)(yao)在(zai)(zai)電(dian)(dian)(dian)力規劃期間明確電(dian)(dian)(dian)網(wang)(wang)負荷(he)的(de)(de)(de)轉移能力,具體包括(kuo)以下(xia)幾方面(mian)內容(rong):①通(tong)常(chang)中(zhong)壓配電(dian)(dian)(dian)網(wang)(wang)應具有40%的(de)(de)(de)備(bei)用(yong)容(rong)量,但如(ru)果(guo)電(dian)(dian)(dian)網(wang)(wang)運行(xing)(xing)期間的(de)(de)(de)某個構件出(chu)現問(wen)(wen)題(ti),就(jiu)(jiu)會對電(dian)(dian)(dian)網(wang)(wang)的(de)(de)(de)正常(chang)運行(xing)(xing)帶來一(yi)定的(de)(de)(de)不利(li)影(ying)響,在(zai)(zai)這種情(qing)況下(xia),就(jiu)(jiu)要(yao)(yao)采取倒(dao)閘操(cao)作的(de)(de)(de)挽(wan)救方式(shi),保(bao)(bao)證電(dian)(dian)(dian)網(wang)(wang)仍然(ran)能夠(gou)為廣大(da)群眾提(ti)(ti)供(gong)(gong)電(dian)(dian)(dian)力支持,防止出(chu)現大(da)面(mian)積停電(dian)(dian)(dian)的(de)(de)(de)現象;②一(yi)旦在(zai)(zai)供(gong)(gong)電(dian)(dian)(dian)期間出(chu)現中(zhong)壓配電(dian)(dian)(dian)技術方面(mian)的(de)(de)(de)問(wen)(wen)題(ti)時(shi)(shi)(shi),就(jiu)(jiu)要(yao)(yao)對其(qi)存在(zai)(zai)的(de)(de)(de)問(wen)(wen)題(ti)及時(shi)(shi)(shi)修復(fu),進行(xing)(xing)達到負荷(he)轉移的(de)(de)(de)目的(de)(de)(de),促使(shi)(shi)(shi)電(dian)(dian)(dian)網(wang)(wang)仍然(ran)可以繼續運行(xing)(xing)。但如(ru)果(guo)是(shi)變電(dian)(dian)(dian)站(zhan)(zhan)出(chu)現問(wen)(wen)題(ti)在(zai)(zai)對其(qi)進行(xing)(xing)修復(fu)時(shi)(shi)(shi),就(jiu)(jiu)要(yao)(yao)保(bao)(bao)證以下(xia)兩(liang)點內容(rong):a.充(chong)分保(bao)(bao)證一(yi)旦變電(dian)(dian)(dian)站(zhan)(zhan)出(chu)現故障(zhang)現象時(shi)(shi)(shi)兩(liang)天(tian)回(hui)路供(gong)(gong)電(dian)(dian)(dian)失(shi)去其(qi)中(zhong)一(yi)條(tiao)時(shi)(shi)(shi),一(yi)定不能對其(qi)供(gong)(gong)電(dian)(dian)(dian)進行(xing)(xing)限(xian)制;b.如(ru)果(guo)變電(dian)(dian)(dian)站(zhan)(zhan)出(chu)現故障(zhang)現象,三條(tiao)回(hui)路中(zhong)的(de)(de)(de)一(yi)條(tiao)回(hui)路失(shi)去不能對其(qi)供(gong)(gong)電(dian)(dian)(dian)進行(xing)(xing)限(xian)制,但若(ruo)是(shi)三條(tiao)回(hui)路中(zhong)的(de)(de)(de)兩(liang)條(tiao)回(hui)路都失(shi)去,就(jiu)(jiu)需要(yao)(yao)充(chong)分保(bao)(bao)證其(qi)供(gong)(gong)電(dian)(dian)(dian)能量達到75%-85%之間,進而(er)在(zai)(zai)變電(dian)(dian)(dian)站(zhan)(zhan)的(de)(de)(de)回(hui)路同時(shi)(shi)(shi)關停時(shi)(shi)(shi),使(shi)(shi)(shi)故障(zhang)回(hui)復(fu)時(shi)(shi)(shi)間和電(dian)(dian)(dian)量恢復(fu)時(shi)(shi)(shi)間相同,為使(shi)(shi)(shi)用(yong)者提(ti)(ti)供(gong)(gong)及時(shi)(shi)(shi)的(de)(de)(de)用(yong)電(dian)(dian)(dian)需求。
三、電力市場化改革對電力規劃的影響
1.更為多元化的主體
有序向(xiang)社會資本放開配(pei)售電(dian)(dian)(dian)業務(wu)以及逐步向(xiang)符合條件(jian)的市(shi)場主體(ti)放開增量配(pei)電(dian)(dian)(dian)投資業務(wu),將使得配(pei)電(dian)(dian)(dian)網(wang)(wang)規劃(hua)的主體(ti)多元(yuan)化。配(pei)電(dian)(dian)(dian)網(wang)(wang)規劃(hua)原(yuan)來是(shi)由電(dian)(dian)(dian)網(wang)(wang)企業的規劃(hua)部門進(jin)行統一(yi)(yi)規劃(hua),在政府(fu)審核通過后(hou),電(dian)(dian)(dian)網(wang)(wang)企業可對該區域配(pei)電(dian)(dian)(dian)網(wang)(wang)進(jin)行建(jian)設。新電(dian)(dian)(dian)改政策下,配(pei)電(dian)(dian)(dian)網(wang)(wang)建(jian)設和(he)規劃(hua)不再(zai)單(dan)一(yi)(yi)地由電(dian)(dian)(dian)網(wang)(wang)企業負責(ze),而是(shi)由投資的多元(yuan)主體(ti)共同(tong)負責(ze),配(pei)電(dian)(dian)(dian)網(wang)(wang)規劃(hua)目(mu)標(biao)函數的經濟性(xing)選擇和(he)約束條件(jian)的確(que)定需要(yao)體(ti)現各投資主體(ti)的利益,這(zhe)對配(pei)電(dian)(dian)(dian)網(wang)(wang)規劃(hua)的協調性(xing)提出了更高的要(yao)求(qiu)。
2.更為多樣化的內容
新電(dian)(dian)(dian)改(gai)政策推進電(dian)(dian)(dian)力交易(yi)體制(zhi)改(gai)革,引導(dao)市(shi)(shi)場主體開展多方直接交易(yi),對配(pei)(pei)(pei)(pei)網(wang)(wang)的(de)(de)規(gui)(gui)(gui)(gui)劃(hua)(hua)內容會(hui)提出(chu)更(geng)(geng)多個性化(hua)的(de)(de)要求,將使配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)網(wang)(wang)規(gui)(gui)(gui)(gui)劃(hua)(hua)的(de)(de)內容多樣(yang)化(hua),對于(yu)配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)網(wang)(wang)規(gui)(gui)(gui)(gui)劃(hua)(hua)流程實(shi)施(shi)方案(an)的(de)(de)選擇和(he)規(gui)(gui)(gui)(gui)劃(hua)(hua)資源的(de)(de)確定(ding)帶來了(le)影響。配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)網(wang)(wang)規(gui)(gui)(gui)(gui)劃(hua)(hua)不單(dan)單(dan)只是對配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)環節進行規(gui)(gui)(gui)(gui)劃(hua)(hua),對于(yu)配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)網(wang)(wang)上下游(you)的(de)(de)輸電(dian)(dian)(dian)、售(shou)電(dian)(dian)(dian)環節也應(ying)在(zai)(zai)配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)網(wang)(wang)規(gui)(gui)(gui)(gui)劃(hua)(hua)中考慮(lv)。通(tong)過制(zhi)定(ding)合理的(de)(de)輸配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)價(jia)格推動輸配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)網(wang)(wang)發展,在(zai)(zai)售(shou)電(dian)(dian)(dian)側(ce)通(tong)過與(yu)上網(wang)(wang)電(dian)(dian)(dian)價(jia)聯動,使得(de)電(dian)(dian)(dian)力市(shi)(shi)場模式能夠(gou)更(geng)(geng)好地適應(ying)與(yu)配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)網(wang)(wang)的(de)(de)運行。在(zai)(zai)配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)網(wang)(wang)規(gui)(gui)(gui)(gui)劃(hua)(hua)中應(ying)用電(dian)(dian)(dian)力市(shi)(shi)場機制(zhi)和(he)售(shou)電(dian)(dian)(dian)側(ce)互動資源,可以更(geng)(geng)好地降低配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)網(wang)(wang)的(de)(de)運營(ying)成本(ben),優化(hua)配(pei)(pei)(pei)(pei)電(dian)(dian)(dian)網(wang)(wang)規(gui)(gui)(gui)(gui)劃(hua)(hua)。
3.潮流不確定性增強
系(xi)(xi)(xi)統(tong)潮(chao)流是指電力系(xi)(xi)(xi)統(tong)的(de)運行狀態(tai),它的(de)計算結(jie)果(guo)是電力系(xi)(xi)(xi)統(tong)穩定(ding)性(xing)(xing)的(de)分(fen)析(xi)以及故障分(fen)析(xi)的(de)基礎。電力市(shi)場改革使(shi)零售商和(he)大用戶(hu)具有了更多的(de)購電的(de)選擇,于是電力系(xi)(xi)(xi)統(tong)潮(chao)流的(de)分(fen)布不均衡,進(jin)而造(zao)成系(xi)(xi)(xi)統(tong)潮(chao)流的(de)不穩定(ding)性(xing)(xing)。
4.電源不確定性增強
在電(dian)(dian)力市(shi)(shi)場改革的(de)(de)(de)作用下,電(dian)(dian)廠與(yu)(yu)電(dian)(dian)網(wang)相(xiang)分離,相(xiang)應的(de)(de)(de),電(dian)(dian)網(wang)規(gui)(gui)劃與(yu)(yu)電(dian)(dian)源(yuan)規(gui)(gui)劃也(ye)就(jiu)相(xiang)互獨立。電(dian)(dian)源(yuan)規(gui)(gui)劃不(bu)與(yu)(yu)電(dian)(dian)網(wang)規(gui)(gui)劃發生聯系,而是與(yu)(yu)電(dian)(dian)廠投(tou)資(zi)(zi)商有著密切的(de)(de)(de)關(guan)聯。投(tou)資(zi)(zi)商為使投(tou)資(zi)(zi)獲得的(de)(de)(de)回(hui)報最大化,在電(dian)(dian)源(yuan)的(de)(de)(de)規(gui)(gui)劃上就(jiu)會有偏(pian)向(xiang)于(yu)投(tou)資(zi)(zi)商一方(fang),在電(dian)(dian)源(yuan)規(gui)(gui)劃的(de)(de)(de)實施、控制(zhi)、調整(zheng)等各個(ge)方(fang)面(mian)都更(geng)多的(de)(de)(de)取決于(yu)未(wei)來(lai)市(shi)(shi)場的(de)(de)(de)電(dian)(dian)價(jia)波動、國家的(de)(de)(de)相(xiang)關(guan)政策(ce)、能源(yuan)的(de)(de)(de)價(jia)格(ge)、負荷的(de)(de)(de)變化等。整(zheng)體上看,電(dian)(dian)源(yuan)規(gui)(gui)劃建(jian)設的(de)(de)(de)不(bu)確定性較高。
四、完善電力市場的改革對規劃的影響
1.探索全新的電網規劃方法
要想增強電(dian)(dian)(dian)網(wang)(wang)規(gui)劃的(de)整(zheng)體是(shi)影響就(jiu)需要在進行(xing)(xing)電(dian)(dian)(dian)網(wang)(wang)規(gui)劃的(de)過程中(zhong)探索全新的(de)電(dian)(dian)(dian)網(wang)(wang)規(gui)劃方法,在進行(xing)(xing)規(gui)劃的(de)過程中(zhong)電(dian)(dian)(dian)網(wang)(wang)企(qi)業(ye)要考慮到自身的(de)經濟(ji)性。在進行(xing)(xing)規(gui)劃的(de)過程中(zhong)要結合企(qi)業(ye)自身的(de)發展情況,在建設的(de)過程中(zhong)降低整(zheng)體的(de)規(gui)劃成本(ben)、建設成本(ben)和整(zheng)體的(de)運行(xing)(xing)成本(ben),在考慮成本(ben)的(de)基礎上(shang)要保證整(zheng)體電(dian)(dian)(dian)網(wang)(wang)的(de)安全與可靠性,同時幫(bang)助(zhu)電(dian)(dian)(dian)網(wang)(wang)企(qi)業(ye)自身獲得更好的(de)經濟(ji)效益。
2.制定全新的電網電價制度
在電(dian)(dian)(dian)力(li)市場改革新(xin)政策的(de)影響下,要想(xiang)提升電(dian)(dian)(dian)網(wang)規(gui)劃的(de)整體質量,應當制定全(quan)新(xin)的(de)電(dian)(dian)(dian)網(wang)電(dian)(dian)(dian)價制度。應當通過(guo)電(dian)(dian)(dian)網(wang)電(dian)(dian)(dian)價制度的(de)改革來探索電(dian)(dian)(dian)網(wang)領域全(quan)新(xin)的(de)盈利形式和發展形式。對于電(dian)(dian)(dian)網(wang)企(qi)業售電(dian)(dian)(dian)但是并沒有參與電(dian)(dian)(dian)網(wang)規(gui)劃和建設的(de)區(qu)域要充分考慮到電(dian)(dian)(dian)網(wang)規(gui)劃的(de)過(guo)程中產生的(de)額外費(fei)用,只要這樣才(cai)能夠實現(xian)自(zi)身的(de)發展。
3.提高電網的自動化水平
在(zai)進(jin)行電(dian)(dian)(dian)網規劃的(de)過(guo)程中,應該結(jie)合現代化(hua)信息(xi)技術(shu)(shu),以提(ti)高(gao)電(dian)(dian)(dian)網規劃的(de)自動化(hua)水平(ping)。自動化(hua)水平(ping)的(de)提(ti)高(gao)能(neng)(neng)(neng)夠提(ti)升(sheng)電(dian)(dian)(dian)網的(de)質量。我(wo)國的(de)電(dian)(dian)(dian)力行業發展受到一定的(de)限制,結(jie)合配電(dian)(dian)(dian)自動化(hua)設備和技術(shu)(shu),能(neng)(neng)(neng)夠提(ti)高(gao)電(dian)(dian)(dian)網規劃的(de)水平(ping),縮小與發達國家的(de)差距。采(cai)用自動化(hua)配電(dian)(dian)(dian)技術(shu)(shu),能(neng)(neng)(neng)夠降低配電(dian)(dian)(dian)故障(zhang)和生產成本,優化(hua)電(dian)(dian)(dian)能(neng)(neng)(neng)資源(yuan)的(de)配置。
四、結語
電力(li)市(shi)場化改革會對(dui)電力(li)規劃工(gong)作產生一(yi)(yi)定的(de)(de)影響。但是我國在電力(li)市(shi)場化背景下開展電力(li)規劃工(gong)作在流(liu)程上還存在一(yi)(yi)定的(de)(de)問題(ti),我們必須認清問題(ti),在進行電力(li)規劃時,充分考慮電力(li)市(shi)場化這一(yi)(yi)大背景。