柴油發(fā)電機(jī)并機(jī)并網(wǎng)的條件和工作原理控制

柴油發(fā)電機(jī)并機(jī)并網(wǎng)的條件和工作原理控制柴油發(fā)電機(jī)組并機(jī)控制問題一．發(fā)電機(jī)組并列運(yùn)行的條件是什么？發(fā)電機(jī)組投入并列運(yùn)行的整個(gè)過程叫做并列。將一臺(tái)發(fā)電機(jī)組先運(yùn)行起來，把電壓送至母線上，而另一臺(tái)發(fā)電機(jī)組啟動(dòng)后，與前一臺(tái)發(fā)電機(jī)組并列，應(yīng)在合閘瞬間，發(fā)電機(jī)組不應(yīng)出現(xiàn)有害的沖擊電流轉(zhuǎn)軸不受到突然的沖擊。合閘后，轉(zhuǎn)子應(yīng)能很快的被拉入同步。（即轉(zhuǎn)子轉(zhuǎn)速等于額定轉(zhuǎn)速）因此發(fā)電機(jī)組并列必須具備以下條件1.發(fā)電機(jī)組電壓的有效值與波形必須相同.2.兩臺(tái)發(fā)電機(jī)電壓的相位相同.3.兩臺(tái)發(fā)電機(jī)組的頻率相同. 4.兩臺(tái)發(fā)電機(jī)組的相序一致.二．什么叫發(fā)電機(jī)組的準(zhǔn)同期并列法？怎樣進(jìn)行同期并列？準(zhǔn)同期就是準(zhǔn)確周期。用準(zhǔn)同期法進(jìn)行并列操作，發(fā)電機(jī)組電壓必須相同，頻率相同以及相位一致，這可通過裝在同期盤上的兩塊電壓表、兩塊頻率表以及同期表和非同期指示燈來監(jiān)視，并列操作步驟如下：將其中一臺(tái)發(fā)電機(jī)組的負(fù)荷開關(guān)合上，將電壓送至母線上，而另一臺(tái)機(jī)組處在待并狀態(tài)。合上同期開頭，調(diào)節(jié)待并發(fā)電機(jī)組的轉(zhuǎn)速，使它等于或接近同步轉(zhuǎn)速（與另一臺(tái)機(jī)組的頻率相差在半個(gè)周波以內(nèi)），調(diào)節(jié)待并發(fā)電機(jī)組的電壓，使其與另一臺(tái)發(fā)電機(jī)組電壓接近，在頻率與電壓均相近時(shí)，同期表的旋轉(zhuǎn)速度是越來越慢的，同期指示燈也時(shí)亮?xí)r暗；當(dāng)待并機(jī)組與另一臺(tái)機(jī)組相位相同時(shí)，同期表指針指示向上方正中間位置，同期燈最暗，當(dāng)待并機(jī)組與另一臺(tái)機(jī)組相位差最大時(shí)，同期表指向下方正中位置，此時(shí)同期燈最亮，當(dāng)同期表指針按順時(shí)針方向旋轉(zhuǎn)時(shí)，這說明待并發(fā)電機(jī)的頻率比另一臺(tái)機(jī)組的頻率高，應(yīng)降低待并發(fā)電機(jī)組的轉(zhuǎn)速，反之當(dāng)同期表指針按逆時(shí)針方向旋轉(zhuǎn)時(shí)，應(yīng)增加待并發(fā)電機(jī)組的轉(zhuǎn)速。當(dāng)同期表指針順時(shí)針方向緩慢旋轉(zhuǎn)，指針接近同期點(diǎn)時(shí)，立即將待并機(jī)組的斷路器合閘，使兩臺(tái)發(fā)電機(jī)組并列。并列后切除同期表開關(guān)和相關(guān)的同期開關(guān)。三．在進(jìn)行發(fā)電機(jī)組的準(zhǔn)同期并列時(shí)，應(yīng)注意什么？準(zhǔn)同期并列是手動(dòng)操作，操作是否順利與運(yùn)行人員的經(jīng)驗(yàn)有很大的關(guān)系，為防止不同期并列，下列三種情況不準(zhǔn)合閘。1．當(dāng)同期表指針出現(xiàn)跳動(dòng)現(xiàn)象時(shí)，不準(zhǔn)合閘，因?yàn)橥诒韮?nèi)部可能有卡帶現(xiàn)象，反映不出正確的并列條件。2．當(dāng)同期表旋轉(zhuǎn)過快時(shí)，說明待并發(fā)電機(jī)組與另一臺(tái)發(fā)電機(jī)組的頻率相差太大，由于斷路器的合閘時(shí)間難以掌握，往往使斷路器不在同期點(diǎn)合閘，所以此時(shí)不準(zhǔn)合閘。3．如果同期表指針停在同期點(diǎn)上不動(dòng)，止時(shí)不準(zhǔn)合閘。這是因?yàn)閿嗦菲髟诤祥l過程中如果其中一臺(tái)發(fā)電機(jī)組的頻率突然變動(dòng)，就有可能使斷路器正好合在非同期點(diǎn)上。四．怎樣調(diào)整并列機(jī)組的逆功現(xiàn)象？當(dāng)兩臺(tái)發(fā)電機(jī)組空載并列后，會(huì)在兩臺(tái)機(jī)組之間，產(chǎn)生一個(gè)頻率差與電壓差的問題。并且在兩臺(tái)機(jī)組的監(jiān)視儀表上（電流表、功率表、功率因數(shù)表），反應(yīng)出實(shí)際的逆功情況，一種是轉(zhuǎn)速（頻率）不一致造成的逆功，另一種是電壓不等造成的逆功，其調(diào)整如下：1．頻率造成逆功現(xiàn)象的調(diào)整：如果兩臺(tái)機(jī)組的頻率不等，相差較大時(shí)，在儀表上（電流表、功表）顯示出，轉(zhuǎn)速高的機(jī)組電流顯示正值，功率表指示為正功率，反之，電流指示負(fù)值，功率指示負(fù)值。這時(shí)調(diào)整其中一臺(tái)機(jī)組的轉(zhuǎn)速（頻率），視功率表的指示進(jìn)行調(diào)整，把功率表的指示調(diào)整為零即可。使兩臺(tái)機(jī)組的功率指示均為零，這樣兩臺(tái)機(jī)的轉(zhuǎn)速（頻率）基本上一致。但是，這時(shí)電流表仍有指示時(shí)，這就是電壓差造成的逆功現(xiàn)象了。2,電壓差造成逆功現(xiàn)象的調(diào)整：當(dāng)兩臺(tái)機(jī)組的功率表指示均為零時(shí)，而電流表仍然有電流指示（即一反一正指示）時(shí)，可調(diào)整其中一臺(tái)發(fā)電機(jī)組的電壓調(diào)整旋鈕，調(diào)整時(shí)，視電流表與功率因數(shù)的指示進(jìn)行。將電流表的指示消除（即調(diào)整為零），電流表無指示后，這時(shí)視功率因數(shù)表的指示，把功率因數(shù)調(diào)至滯后0.5以上即可.一般可調(diào)整至0.8左右,為最佳狀態(tài)。五、發(fā)電機(jī)保護(hù)回路1．逆功逆功現(xiàn)象是由發(fā)電機(jī)組轉(zhuǎn)速（頻率）及電壓不同而造成的，即一臺(tái)發(fā)電機(jī)組帶正功，而另一臺(tái)機(jī)組帶負(fù)功率。也就是說帶負(fù)功率的機(jī)組，這時(shí)變成了一個(gè)負(fù)載（此機(jī)組頻率低，轉(zhuǎn)速不一致的現(xiàn)象）。電壓不相同時(shí)，電壓高的機(jī)組，向電壓低的機(jī)組，提供一個(gè)無功電流與無功電壓（此機(jī)組的電流表正向指示），相當(dāng)于在本供電系統(tǒng)內(nèi)，加了一個(gè)調(diào)相機(jī)組。電壓低的機(jī)組，這時(shí)成為一個(gè)大的負(fù)載，接受一個(gè)很大的無功電流，來維持兩臺(tái)機(jī)組的電壓平衡（此機(jī)組的電流表反向指示）。監(jiān)測(cè)時(shí)把某一臺(tái)機(jī)組的電壓調(diào)高，或?qū)⒘硪慌_(tái)機(jī)組電壓高低，造成一臺(tái)機(jī)組有逆功電流，其動(dòng)作電流為額定電流20%左右。逆動(dòng)繼電器動(dòng)作、跳閘、報(bào)警，但不停機(jī)。2．過電流：現(xiàn)在的發(fā)電機(jī)組額定功率一定的，它的超載能力很低，基本上在額定功率的5%左右，允許帶載時(shí)間15~30分鐘，最多不超60分鐘，超過這個(gè)時(shí)間，發(fā)電機(jī)組會(huì)發(fā)熱，導(dǎo)線絕緣會(huì)降低，也就降低了使用壽命。所以在設(shè)定過電流保護(hù)時(shí)無特殊要求的，過電流保護(hù)設(shè)定在額定電流的110%即可。帶載測(cè)試時(shí)，將電流帶至額定流的110%，過流繼電器動(dòng)作。跳閘、報(bào)警、不停機(jī)。3．過電壓：在并列使用發(fā)電機(jī)組時(shí)最怕供電系統(tǒng)發(fā)生振蕩，一但發(fā)生振蕩系統(tǒng)電壓升高，易造成用電設(shè)備及供電設(shè)備的絕緣擊穿，使供電設(shè)備與用電設(shè)備一起癱瘓。為此并列使用的發(fā)電機(jī)組均裝有過電壓保護(hù)，其設(shè)定值為額定電壓的105%為最佳。短接過電壓繼電器，跳閘停機(jī)、報(bào)警動(dòng)作.（六）分合閘回路分、合閘回路均接入手機(jī)并列，自動(dòng)并列的控制回路。1．手動(dòng)分合閘：每臺(tái)機(jī)組均可做為首機(jī)或待并分、合閘使用，在手動(dòng)并車或供電時(shí)，使用手動(dòng)分合閘。2．自動(dòng)分合閘：每臺(tái)機(jī)組均可選擇為待并機(jī)組，或首臺(tái)機(jī)組；首機(jī)機(jī)組自啟動(dòng)后，合閘回路自動(dòng)合閘，自動(dòng)投入及退出同期。同期后把待并機(jī)組自動(dòng)合閘并列運(yùn)行。3．無論是手動(dòng)合閘，還是自動(dòng)合閘，一旦機(jī)組出現(xiàn)逆功，過了低油壓、高水溫、高水溫、高油溫、過電壓，全部自動(dòng)分閘解列與負(fù)載脫離。（七）同期回路1．當(dāng)首機(jī)合閘后把電源送至母線，這時(shí)母線檢測(cè)同期回路，與待并機(jī)的同期回路，接到信號(hào)后，自動(dòng)合上同期檢測(cè)繼電器。將母線電壓與待并機(jī)電壓送至同期控制模塊，模塊自動(dòng)檢測(cè)，并列機(jī)組的電壓與轉(zhuǎn)速。如果轉(zhuǎn)速有差別時(shí)，同期模塊自動(dòng)調(diào)整待并機(jī)轉(zhuǎn)速，使其達(dá)到并列條件。找到同期點(diǎn)后同期模塊發(fā)出合閘指令，待并機(jī)組接到指令后執(zhí)行合閘，即兩臺(tái)機(jī)組并列運(yùn)行。2．機(jī)組并列后，同期回路自動(dòng)退出工作狀態(tài)，但必須人為的把自動(dòng)同期的轉(zhuǎn)換開關(guān)退出，防止來電后在解列時(shí)，待并機(jī)組又接到并列信號(hào)，將同期裝置自動(dòng)投入，使機(jī)組再次并列。（八）負(fù)載分配1．單機(jī)運(yùn)行時(shí)，負(fù)載分配器不投入工作。2．機(jī)組并列后每臺(tái)機(jī)組的負(fù)載分配器，同時(shí)投入工作，各自調(diào)整自已的轉(zhuǎn)速，使其兩臺(tái)機(jī)組的功率平均分配，其工作原理，就是根據(jù)本機(jī)組的輸出功率的大?。措娏鞯拇笮。?，自動(dòng)調(diào)整丁機(jī)組的轉(zhuǎn)速，使其負(fù)載平（九）電壓調(diào)整回路1．機(jī)組并列前，必須把兩臺(tái)機(jī)組的電壓調(diào)整在同一數(shù)值上。2．空載并列后，調(diào)整電壓旋鈕，把逆功現(xiàn)象消除，使其功率因數(shù)在滯后0.8左右即可。3．并列機(jī)組帶載后，可根據(jù)負(fù)載情況，手動(dòng)調(diào)節(jié)電壓調(diào)整旋鈕，使其功率因數(shù)在最佳位置，以后可不用再調(diào)整。（十）速度調(diào)整回路1．并列前必須把兩機(jī)組的速度（頻率）調(diào)整一致。2．并列時(shí)，可根據(jù)同期表的轉(zhuǎn)動(dòng)速度，調(diào)節(jié)首機(jī)或待并機(jī)組的轉(zhuǎn)速，使同期表轉(zhuǎn)動(dòng)方向，按順時(shí)針或逆時(shí)針方向轉(zhuǎn)動(dòng)，速度越慢越好，但同期表的指針必須轉(zhuǎn)動(dòng)才能并列。3．并列后，觀察兩臺(tái)機(jī)組的電流、功率是否平衡，如差別太大，可調(diào)整速度旋鈕，將兩臺(tái)機(jī)組的功率（十一）儀表檢測(cè)回路1．操作前，必須把各種相關(guān)的儀表調(diào)改至零，但功率因數(shù)表與頻率表不在零處。2．操作時(shí)，觀察各種儀表的運(yùn)行狀態(tài)，是否符合規(guī)定（有無儀表接線接反的現(xiàn)象）。3．電流、電壓、要使用有關(guān)儀表與之檢驗(yàn)一下，看指示數(shù)值是否正常。（十二）啟動(dòng)回路1．操作前必須首先檢查啟動(dòng)回路是否正常。2．啟動(dòng)后相關(guān)元件是否能夠正常工作。3．啟動(dòng)機(jī)與主機(jī)的結(jié)合是否正常，能否退出。（十三）停機(jī)回路1．停機(jī)電磁鐵與電磁閥動(dòng)作是否可靠。2．在機(jī)組發(fā)生故障時(shí)，是否自動(dòng)停機(jī)。3．手動(dòng)停機(jī)回路是否完善。4．只需跳閘時(shí)，是否停機(jī)等現(xiàn)象。ConditionsandworkingprincipleofdieselgeneratorsandmachinegridDieselgeneratorsetandcontrolA.Whataretheconditionsofparalleloperationofgeneratorsets?Generatingunitsputintoparalleloperationofthewholeprocessiscalledparallel.Ageneratorsetupandrunning,thevoltagesenttothebusafterthestartofanothergeneratingunitswithageneratingsetsidebysideintheclosingmoments,thecurrentgeneratorsetshouldnotbeaharmfulimpact,theshaftnotsubjecttosuddenimpact.Afterclosing,therotorshouldbeabletoquicklypulledintosynchronization.（Ie,therotorspeedisequaltotheratedspeed）generatorgrouptiedfortheRMSandwaveformofageneratorsetvoltagemustmeetthefollowingconditionsmustbethesamethesame.Twogeneratorvoltagephase3.Twogeneratingunitsatthesamefrequency.（4）thephasesequenceofthetwogeneratingunits.Two.Whatisthequasi-synchronizationofthegeneratorsetsidebyside?HowJuxtaposition?Thequasi-synchronizationisaccuratecycle.Quasi-synchronizationmethodforparalleloperation,thegeneratorsetvoltagemustbethesame,thesamefrequencyandphase-coherenttwovoltmetermountedontheplateofthesameperiod,twofrequencytableandthesameperiodinthetableandasynchronousindicatortomonitortheparalleloperationasfollows:Oneofthegeneratingunitsoftheloadswitchisclosed,thevoltagesenttothebus,whiletheotherunitsinthependingandstatus.Closeonthesameperiodinthebeginningofadjustmenttobethespeedofthegeneratorset,makingitequaltoorclosetosynchronousspeed(withanotherunit,thefrequencydiffereneeoflessthanhalfacycle),regulatingthevoltagetobegeneratingsetstomakeitwithanothervoltageofthegeneratorsetcloseinfrequencyandvoltagearesimilartothesameperiodinthetablerotationspeedisgettingslowerandsloweroverthesameperiodindicatorlightanddark;beandtheunitwithanotherunitphase,thetablepointeroverthesameperiodindicateupwardFounderintermediateposition,thesameperiodinthelightmostdark,themaximumphasedifferencewithanotherunitwhentheunitbeandthesameperiodinthetablepointtoalocationundertheFounder,thesameperiodinlightofthebrightest,whenthesameperiodinthetablepointerclockwiseThisshowsthattobeandthegeneratorfrequencyishigherthanthefrequencyoftheotherunits,shouldreducethewaitandthespeedofthegeneratorsetstobeandthespeedofthegeneratorsetshouldbeincreased,andviceversawhenthesameperiodinthetablepointerbycounterclockwiserotation.Whentablepointeroverthesameperiodtheslowclockwiserotation,thepointerclosetothepointofthesameperiod,immediatelywillbetheunitcircuitbreakerclosing,thetwounitssidebyside.Tiedaftertheremovalofthesameperiodinthetableswitchandswitchofthesameperiod.Three.Duringthequasi-synchronizationofthegeneratorsetsidebyside,attentionshouldbewhat?Quasi-synchronoustiemanualoperation,operatingsmoothlyandtheexperienceoftheoperatingpersonnelhaveagreatrelationship,inordertopreventdifferentperiodtied,thefollowingthreeconditionsarenotallowedtoswitchon.A.Whenthesameperiodinthetablepointerjumpsarenotallowedtoswitchon,becausewithinthesameperiodinthetablemayhaveacassette,anddonotreflectthecorrectparallelconditions.Two.Whenrapidtablerotationduringthesameperiod,indicatingthatmuchdifference,beandthefrequencyofthegeneratorsetsandothergeneratingunitsoftenthebreakerisnotinthesameperiodinpointofclosingthecircuitbreakerclosingtimeisdifficulttograsp,sointhiscasearenotallowedtoclosing.3.Tablepointeroverthesameperiodparkedinthesameperiodpointdoesnotmove,onlywhenyouarenotallowedtoswitchon.Thisisbecausethecircuitbreakerintheclosingprocess,ifonegeneratingunitsatthefrequencyofsuddenchangesincircuitbreaker,itispossibletomakepreciselyintheasynchronouspoint.Four.Howtoadjusttheparallelphenomenonofreversepowerunit?Whenthetwounitsemptytied,resultinginapoorfrequencyandvoltagedifferencebetweenthetwounits.Andmonitoringofthetwounitsonthemeter(ammeter,powermeter,powerfactormeters),reflecttheactualreversepower,aspeed(frequency)isinconsistentreversepower,anotherisavoltagerangingfromcausingreversepower,adjustedasfollows:A.Frequencycausedbythephenomenonofreversepoweradjustment:Ifthetwounitsoffrequencyrange,thedifferenceislarge,onthemeter(ammeter,powerTable)show,theshowcoincidedwiththehighspeedoftheunitcurrent,andpowermeterindicatesapositivepower,onthecontrary,thecurrentdirectionsnegativepowerindicatenegativevalues.Thenadjustthespeedofoneunit(frequency),dependingonthepowermeterinstructionstoadjusttotheinstructionsofthepowermeteradjustedtozerocanbe.Twounitsofpowerdirectionsarezero,sothespeed(frequency)ofthetwomachinesarebasicallythesame.However,whentheammeterstillindicate,thisisthevoltagedifferencecausedbythereversepowerphenomenon.thevoltagedifferencecausedbythephenomenonofreversepoweradjustment:Whenthepowermeterindicationofthetwounitsarezero,whiletheammetercurrentinstructions(ieareversalofapositiveindication),adjustthevoltageofthegeneratorsetstoadjustknobadjustment,dependingontheammeterwiththeinstructionsofthePowerFactor.Ammeter'sinstructionstoeliminate(ieadjustedtozero),noindicationammeter,thentheinstructionsinthetableofpowerfactor,laggingpowerfactortomorethan0.5canbeadjustedto0.8,thebeststate.Generatorprotectioncircuit1.Theinversefunctioninversefunctionphenomenoniscausedbythespeed(frequency)andthevoltageofthegeneratorset,generatingunitswithapositiveworkWhiletheotherunitwithnegativepower.Inotherwordswithanegativepoweroftheunit,thenbecomeaload(lowfrequencyofthisunit,thespeedofinconsistency).Voltageisnotthesame,thehighvoltageoftheunitlowvoltageunit,areactivecurrentandreactivepowerandvoltage(thisunitammeterpositiveindication),whichisequivalenttothepowersupplysystem,plusaphasemodulationunit.Lowvoltageoftheunit,thenbecomeabigload,toacceptalargereactivecurrenttomaintainthevoltagebalanceofthetwounits(thisunittheammeterreversedirections).Monitoringtoincreasethevoltageofaunitoranotherunitvoltagelevel,resultinginaunitwithinversereactivecurrent,theoperatingcurrentforabout20%oftheratedcurrent.Theinversedynamicrelaytripping,thepolice,butwithoutstoppingthemachine.Two.Overcurrent:nowthegeneratorsetpowerratingcertain,theoverloadcapacityisverylow,basicallyallowedtoloadinabout5%oftheratedpower,15to30minutes,doesnotexceed60minutes,morethanthistime,thegeneratorsetfever,wireinsulationwillbereduced,reducingtheservicelife.Nospecialrequirementssetovercurrentprotection,overcurrentprotectionissetat110%ofratedcurrent.Withthetestset,thecurrentto110%ofratedflow,over-currentrelay.Trip,alarm,stopmachine.Over-voltage:tiedtouseofthegeneratorsetsaremostafraidofthepowersystemoscillations,buttheoccurrenceoftheoscillationsystemvoltageincreases,couldeasilyleadtothebreakdownofinsulationofelectricalequipmentandpowerequipment,powersupplyequipmentandelectricalequipmentwithparalysis.Usedforthisparallelgeneratorsetsareequippedwithovervoltageprotection,105%ofratedvoltagesetvalueforthebest.Shorttakeovervoltagerelay,tripdown,thealarmaction.(F)andclosingthelooppoints,closingtheloopareconnectedtomobilephonessidebyside,theautomaticcontrolloopinparallel.A.Ofopeningandclosingmanually:eachunitcanbedone,ledbymachineortobeopeningandclosingtouseinthemanualcarorpowerofopeningandclosingmanually.Two.Ofopeningandclosingautomatically:eachunitcanchoosetobeandcrew,orthefirstunit;sincethelaunchofthefirstmachineunit,theclosingloopoftheautomaticswitchon,automaticinputandexitthesameperiod.Overthesameperiodafterthewaitandtheunitautomaticallyclosinginparalleloperation.3.Manualclosingorautomaticclosing,oncetheunitisthereversepower,overalowoilpressure,hightemperature,hightemperature,highoiltemperature,over-voltage,allautomaticgatesplittingandloadout.(7)Inthesameloop.Poweraftertheclosingofthefirstmachinesenttothebuswhenthebusdetectionofsynchronouscircuit,beandthemachinesynchronouscircuit,thereceivedsignal,automaticallyclosesynchronismcheckrelay.Senttothesameperiodthevoltageofthebusvoltagetobeandmachinecontrolmodule,themoduleautomaticallydetectsthevoltageandspeedoftheparallelunits.Ifthespeeddifference,thesameperiodinmoduleautomaticallyadjuststobeandmachinespeedtoreachtheparallelconditions.Issueclosinginstructionstofindthesameperiodpointoverthesameperiodmodulebeandcrewreceivedinstructionsexecutedaftertheclosingoftwounitsinparalleloperation.Two.Unitssidebyside,thesynchronouscircuitautomaticallywithdrawfromtheworkstate,butitmustbeman-madeautomaticallyoverthesameperiodofthechangeoverswitchtoexit,topreventcallsaftersplitting,tobeandtheunitalsoreceivedparallelsignalsynchronizingdeviceautomaticallyputintotheunitonceagainsidebyside.(H)Theloaddistribution1.Stand-aloneruntime,loaddistributordoesnotwork.Two.Unitssidebyside,eachunitoftheloaddistributor,atthesametimetowork,eachtoadjusttheirownspeed,twounitsofpowerevenlydistributed,thesizeofitsworkingprincipleisbasedonthesizeoftheoutputpowerofthisunit(ie,current)toautomaticallyadjustthespeedofthesmallunitstomakeitloadlevel(Ix)thevoltageregulationloopA.Unitssidebysidebefore,thevoltageofthetwounitsmustbeadjustedatthesamevalue.Two.No-loadsidebyside,toadjustthevoltageknobtoeliminatethephenomenonofreversepower,powerfactorcanlag0.8.3.Tiedtotheunitload,dependingontheloadsituation,manuallyadjustthevoltageadjustmentknob,sothatpowe