Sizing of Converters Interfacing the Rotor of Wind Driven DFIG to the Power Grid

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Smat Gid and enewable Enegy,,, 3-34 doi:.436/ge..334 ublihed Online Augut (http://www.si.

1 Smat Gid and enewable Enegy,,, 3-34 doi:.436/ge..334 ublihed Online Augut ( Sizing of Convete Intefaing the oto of Wind Diven DFIG to the owe Gid Mahmoud Abdel Halim Saleh, Mona Naguib Ekande owe Eletoni and Enegy Conveion Depatment, Eletoni eeah Intitute, Caio, Egypt. eeived Apil 9, ; evied May 9, ; aepted May 6,. ABSTACT In thi pape, the opeation of the Double Fed Indution Geneato (DFIG) in the ange fom ynhonou peed down to ub-ynhonou peed i analyzed uing the powe-flow appoah. The objetive of thi analyi i to detemine a eiling fo the ating of the onvete intefaing the oto of the wind diven double fed indution geneato (DFIG) to the gid. Sizing the onvete i an impotant iue in detemining the eonomi viability of uing the DFIM a a geneato at ynhonou and ub-ynhonou peed in wind enegy onveion ytem. The ize of the onvete i poved to be le than % of the ated powe of the DFIG, whih i 4% to 67% lowe than that etimated in peviou publiation. Keywod: Double Fed Indution Geneato, Convete Sizing, Cot loweing, Wind Enegy Conveion Sytem. Intodution The wold ommunity i vey muh onened about limate hange and peifially the global waming, whih i mainly attibuted to the ineae of geenhoue gae (GHG) in the atmophee. The GHG ae mainly podued due to buning foil fuel (oil deivative, natual ga, and oal) and othe ogani matte (bioma) fo powe geneation o othe indutial pupoe. The utilization of enewable enegy eoue (hydo, wind and ola) a altenative to foil fuel an mitigate the poblem of GHG ineae in the atmophee. Mot of the hydo-enegy eoue all ove the wold, (exept in ome pat of the Afian ontinent), ae being utilized fo eleti powe geneation. The eond in ow of enewable enegy eoue i the wind, whih i onideed the mot pomiing and fatet gowing enegy eoue woldwide. The Global Wind Enegy Counil in Buel, announed on Febuay, that the wold wind powe intalled apaity gew by 3% in 9, adding 37.5 GW to bing the total intalled apaity of wind enegy onveion ytem up to 58 GW. The ontinued apid gowth in wind powe apaity, depite the woldwide finanial ii and eonomi downtun, i tetament to the inheent attation of wind ytem due to thei envionmental, eonomi, and tehnial meit. Howeve, wind enegy utilization ha, beide the many meit, two main dawbak, namely; the intemittent unpeditable natue of the wind eoue, and the elatively lage invetment ot of the omponent of the wind enegy onveion ytem (WECS).Of oue, the natue of the wind ould not be hanged, but WECS ould be onneted to lage powe gid, and opeate a fuel ave duing the availability of eaonable wind peed, while the foil fuel fied powe plant onneted to the gid at a bakup duing the low wind peed. At thi point, the advantage of adjutable peed wind geneato (ASG) hould be mentioned, ine thi type of WECS an geneate at all powe level and an extat the imum amount of enegy fom the available wind peed. The ASG ae moe ot effetive than the fixed peed geneato. They, alo, have le mehanial tee, impoved powe quality, and ineaed tability magin of the eleti powe gid. The ASG an futhe be ubdivided into two type, eithe thoe baed on ynhonou geneato, o thoe baed on doubly fed indution geneato (DFIG). The DFIG baed WECS dominate beaue of the ignifiant edution of the powe ating and ot of the onvete, the poible peed egulation fo optimal utilization of enegy, the poibility of ontolling the eative powe, and finally the poibility of ub-ynhonou, ynhonou, and upe-ynhonou opeation of the indution geneato. Mot, if not all the old WECS duing the lat Copyight Sie.

2 Sizing of Convete Intefaing the oto of Wind Diven DFIG to the owe Gid 3 yea, ae DFIG-baed ytem. The maket hae of DFIG ytem (75%) upaed many time the othe type of WECS. In thi pape, the ize and onequently the ot of one of the main eletial omponent of the DFIG-baed WECS, namely, the onvete, i invetigated. It i poved that the ize of the onvete (% of ated DFIG powe) i muh le than etimated in peviouly publihed [] pape (5% - 3%). The behavio of the DFIG at ynhonou peed i alo invetigated.. The owe Handled by the Convete in the Sub-Synhonou ange The behavio of the eleti powe geneating ytem i uually govened by the demand ide (eleti load, gid equiement, et.). The pime move (foil fuel fied tubine, hydo-tubine, dieel engine, et.) ae alway eponding to the need of the powe gid o load. In the ae of WECS, thei behavio i govened mainly by the upply ide, namely, the wind eoue (wind peed and wind powe). Thu it i moe logial that any analyi of the pefomane of WECS tat fom the pime move ide, i.e. wind tubine. All manufatued vaiable peed wind tubine ae pith ontolled type. Between the ut-in wind peed and the ated wind peed, the angula peed of the wind tubine and onequently the DFIG oto peed hange to maintain an optimal tip peed atio fo imum enegy yield. Geneally peaking, wind tubine ae un along the o alled imum powe point taking [] uve. Figue how the mot patially adopted hape fo vaiation of the output mehanial powe of the wind tubine veu the geneato angula peed. It how a quadati hape fom the ut-in peed, to the ated peed, whih oepond to the ut-in and ated wind peed epetively. The DFIG ha it own ynhonou peed oeponding to it numbe of pole and powe fequeny of the gid to whih it i onneted. The value of i uually 5% to % highe than. It i well known [3] that the powe flowing in the oto of the DFIG ha thee omponent; namely, the mehanial powe input to the oto fom the wind tubine m, the eletomagneti powe tanfeed fom oto to tato g, and the lip powe whih i the eletial powe tanfeed between the oto and any extenal eletial oue o load (e.g. onvete) via the wound oto lip ing. i patially onumed in oto winding a oppe loe and may be witten a:, whee u i powe handled by onvete and u i oto oppe loe. Thee omponent ae inte-elated a follow unde any ondition: Figue. Typial powe-wind peed haateiti. g m m g g, whee i the oto lip. Negleting the mehanial loe in the oupling, geabox, and the oto, then the mehanial powe input to the oto will be equal to the output powe of the wind tubine. m = t The negative ign indiate that t i the tubine output while m i DFIG input In the peed ange fom to the mehanial powe input to the DFIG at any angula peed an be expeed a: m k k i a ontant () At the oto angula peed oeponding to ated wind peed, the input mehanial powe m i given a: m k () Fom Equation () and () and onideing: the input mehanial powe to the oto of DFIG an be expeed a: m m (3) whee and ae the oto lip oeponding to the ated and ut-in oto angula peed epetively. Sine the amount of mehanial powe onveted to eletial powe by the DFIG ould not exeed the output powe of the wind tubine, theefoe, the lip powe (whih i appoximately equal to the powe handled by the onvete), ould not exeed, at any lip, the value given by the following Equation: m m (4) Copyight Sie.

3 3 Sizing of Convete Intefaing the oto of Wind Diven DFIG to the owe Gid Figue how the vaiation of the pe unit value of m, g, and a funtion of the lip in the ange fom ut-in to the ynhonou oto peed fo an aumed patial value of =.5 Alo, the vaiation of the pe unit value of veu the lip i hown in Figue 3, in enlaged ale. It i lea fom Figue 3 that thee exit a lip at whih the magnitude of the lip powe ha a imum value. Thi value of lip i detemined by equating the deivative of to zeo, i.e. d /d =. Diffeentiating Equation (4) and, equating the deivative to zeo, and manipulating give the following Equation: (5) The thee oot of Equation (5) ae: and The only valid oot whih lie between the ut-in and ated peed i: (6) In patie the ated angula peed of the wind tubine ange fom the ut in peed ( =.5 to.5 ). Knowing that the ated peed i 5% to % highe than the ynhonou peed of the DFIG, then the patial ange of i between.35 and.6. Theefoe, the lip powe, (o appoximately the powe handled by the onvete = u ) ould not exeed the value given in Equation (7): (7) m p.. u The pe unit imum powe handled by the onvete i hown in Figue 4 a funtion of the ut-in lip within the patial ange of =.35 to.6. Figue 4 how that the powe handled by the onvete ange between 3.6% and 9.68% of the DFIG ated mehanial powe, whih i lightly le than the ated ai gap powe and onequently the ated output of the DFIG. The lowe the value of (the lage the value of the ut-in angula peed), the malle will be the ize of the onvete. The value of =.5 i a vey ommon patie, i.e. the ated peed i appoximately double the ut-in peed, and the oeponding onvete ize will not exeed 7.5% of the DFIG ated powe. Sine the ot of onvete depend mainly on it ating in appoximately linea elation, then when popely eleting the onvete it ot will be edued by 4% to 67% of that etimated in peviou publiation []. Fo the.5 MW to 3 MW ize (8) (p.u.) m,g,(p.u.) m g SLI Figue. Vaiation of m, g, and with lip SLI Figue 3. Vaiation of the pe unit value of veu the lip. (magnitude) S Figue 4. Maximum powe handled by the onvete. WECS, the ot of the powe onvete ange between 6.4% and.5% of the total WECS omponent ot. Theefoe the pope eletion of the DFIG powe onvete ize will edue the total ytem ot fom.5% to Copyight Sie.

4 Sizing of Convete Intefaing the oto of Wind Diven DFIG to the owe Gid 33 8%. 3. The owe Handled by the Convete at Synhonou peed The analyi in Setion of thi pape, applie to the opeation of DFIG fom the ut-in peed up to jut befoe the ynhonou peed i.e. <. Thi etion i devoted to the opeation of the DFIG at ynhonou peed i.e. =, whee the DFIG will opeate a a ynhonou geneato. The ated powe of the DFIG i alulated duing the deign phae a being the mahine output when the oto i hot iuited. It ould be eaily poved that [3]: g me (9) whee g = ated ai gap powe = ated output powe (negleting the tato loe) m = numbe of phae of the DFIG E oto indued voltage at tand till oto eitane = atio of tand-till oto leakage eatane to the oto eitane m g me () Fom Equation () and (), the input mehanial powe at any lip an be expeed a: me m At ynhonou peed i.e. = m o me () () Fom the DFIG oto ide, following the oto powe flow appoah a given in ef. [3], imum ai gap powe tanfeed fom the oto to the tato of the DFIG at any lip i expeed a gm me (3) whee i the atio of the onvete output voltage to the tand-till oto indued voltage. gm i a ontinuou funtion of the lip fom the ubynhonou to the upe-ynhonou ange, theefoe at ynhonou peed the value of g at = an be expeed a g me limit gm (4) The mehanial powe input to the oto, if the mehanial loe ae negleted, will be onveted to eletial powe tanfeed to the tato though the ai gap. Equating m and g at = fom Equation () and (4), the following expeion fo an be obtained (5) o Theefoe the value of the d.. voltage output of the onvete V, that keep the DFIG onveting all it mehanial input powe into eletial powe i given a : V E (6) The vaiation of at = with the ut-in peed at a value of ated lip =.5 i hown in Figue 5 fo diffeent value of. It i lea fom Figue 5 that the d.. voltage output of the onvete ineae with the ineae of the ut- in lip. Thu the highe the value of, the lowe will be the value of. atially, the value of fo lage DFIG i in the ange fom 8 to, and the ut-in lip i aound the value of.5. Theefoe, the d.. voltage applied to the oto iuit of the DFIG at ynhonou peed will ange between 3.4% - 3.6% of the oto indued voltage of tand-till. The powe handled by the onvete and at the ame time onumed in the oto iuit, i a vey impotant paamete when aeing the pefomane of the DFIG opeating a a ynhonou mahine V V I e (7) Fom Equation (), (5) and (6), the pe unit value of the powe handled by the onvete (o onumed in the oto iuit) an be expeed a: (8) pu whee, 4 Figue 6 how the vaiation of the onvete pe-unit powe with the ut-in peed fo diffeent value of. Thi powe ange between.8% and 3% of the ated value within the patial ange of (8 ) and =.5. Thi powe i equivalent to the powe of the exite of a ynhonou mahine. Copyight Sie.

5 34 Sizing of Convete Intefaing the oto of Wind Diven DFIG to the owe Gid onvete(p.u.) B= B=6 B=8 B= S = Figue 5. The vaiation of with the ut-in peed. onvete(p.u.) B=4 B=6 B=8 B= S= S Figue 6. The vaiation of onvete powe with ut-in peed. 4. Conluion Opeating the DFIM a a geneato at ynhonou peed i diued. The magnitude of the oto applied voltage eential fo onveting the mehanial output of the wind tubine into eletial powe at ynhonou peed i deived. Alo, equation fo the powe handled by the onvete at ynhonou and ub-ynhonou peed ae deived. Thee equation poved that the ize of the onvete i le than % of ated DFIG powe, whih i 4% to 67% lowe than the etimated ize in peviou publiation. Thi onluion i in favo of deployment of DFIG a geneato at ynhonou and ub-ynhonou peed due to it lowe ot when ompaed to onventional ynhonou geneato that need full powe tato onvete fo powe onditioning. Anothe advantage i it bette effiieny, ine moe enegy an be aptued fom the available wind. Sine the ot of onvete depend mainly on it ating in appoximately linea elation, then when popely eleting the onvete it ot will be edued by 4% to 67%. Fo the.5 MW to 3 MW ize WECS, the ot of the powe onvete ange between 6.4% and.5% of the total WECS omponent ot. Theefoe the pope eletion of the DFIG powe onvete ize will edue the total ytem ot fom.5% to 8%. Thi ot edution enue the eonomi viability of WECS baed on doubly fed indution geneato (DFIG). The eult obtained in thi pape ould be vey helpful fo the deigne of WECS by eleting the pope ize of the onvete. EFEENCES [] J. Hu and Y. He, einfoed Contol and Opeation of DFIG-Baed Wind owe Geneation Sytem unde Unbalaned Gid Voltage Condition, IEEE Tanation on Enegy Conveion, Vol. 4, No. 4, Deembe 9, pp doi:.9/tec [] D. Saidani, O. Hanaoui and. Dhifaoui, Contol of Double Fed Indution Geneato fo Wind Conveion Sytem, Intenational Jounal of Siene and Tehnique of Automati Contol & Compute Engineeing, Vol., No., Deembe 8, pp [3] M. A. Saleh and M. N. Ekande, Sub-Synhonou ange of Opeation fo a Wind Diven Double-Fed Indution Geneato, Jounal of owe Eletoni, Vol., No., Januay. Lit of Symbol lip powe onvete powe m mehanial powe g ai gap powe u oto oppe loe V onvete output voltage I onvete (oto) uent E indued voltage oto at tand till oto eitane lip lip at whih lip powe i imum oto angula peed atio of onvete to tandtill oto indued voltage atio of tandtill oto leakage eatane to oto eitane Subipt ut in value ated value p.u. pe unit value Copyight Sie.

LECTURE 24 INDUCTION MACHINES (1)

ECE 330 POWER CIRCUITS AND ELECTROMECHANICS LECTURE 24 INDUCTION MACHINES (1) Acknowledgment-Thee handout and lectue note given in cla ae baed on mateial fom Pof. Pete Saue ECE 330 lectue note. Some lide