Determination of Excitation Capacitance of a Three Phase Self Excited Induction Generator

Transcription

1 ISSN (Online): (An ISO 397: 007 Cetified Oganization) Detemination of Excitation Capacitance of a Thee Phae Self Excited Induction Geneato Anamika Kumai, D. A. G. Thoa, S. S. Mopai 3 PG Student [EMD], Dept. of EE, Govt. College of Engineeing, Auangabad, Mahaahta, India Aociate Pofeo and Head, Dept. of EE, Govt. College of Engineeing, Auangabad, Mahaahta, India Aitant Pofeo, Dept. of EE, Govt. College of Engineeing, Auangabad, Mahaahta, India 3 ABSTRACT: The depletion of foil fuel in the wold, ha given ie to the impotance of non-conventional enegy ouce. Wind tubine and mico hydo geneato with induction geneato ae conideed a an altenative choice. Wind tubine with Self-excited Induction Geneato (SEIG) ae inceaingly being ued to geneate clean enewable enegy. SEIG ae widely being ued in iolated aea (ual aea) to geneate electical enegy. Capacito bank ae ued with a pupoe to povide eactive powe fo it excitation. The nonlineaity of the magnetizing inductance and the vaying oto peed neceitate the calculation of excitation capacitance equied fo voltage build up in a SEIG. Thi pape peent the vaiou appoache fo detemining the excitation capacitance and evaluate the value of excitation capacito fo 0/380V,.4/7.A, 4 pole, 50Hz induction machine though vaiou appoache, to build-up voltage fo iolated opeation of a elf-excited induction geneato. KEYWORDS: elf-excited induction geneato, excitation capacitance, teady tate model, tanient model I. INTRODUCTION With the depletion of enegy ouce woldwide, evey effot i made to convet othe fom of non-conventional enegie into electical enegy. Theefoe enegy ecovey cheme ae becoming an impotant apect of peent day indutial pocee. In the coatal aea, wind enegy i available in abundance. The wind tubine tap the wind enegy and convet mechanical powe to electical powe. Thi can be accomplihed by an electic geneato which can be a DC machine, a ynchonou machine, o an induction machine. The peence of commutato in DC machine make it low eliable and inceae the maintenance cot. The ynchonou geneato ae uitable fo contant peed ytem. Pemanent magnet ynchonou geneato ae not uited fo iolated opeation, ince thei geneated voltage tend to fall teeply with load. Fo the conveion of the wind enegy into electical enegy, an induction machine coupled with a windmill offe an ideal olution. They ae of two type. Wound oto type i expenive and equie inceaed maintenance, theefoe only ued whee (i) the diven load equie peed contol o (ii) high tating toque i equied. Hence it i a pefeed choice in gid connected wind geneation cheme. In gid connected mode (without uing convete), the teminal voltage and fequency of the geneato ae fixed and detemined by the gid. The quiel cage type i imple and moe economical in contuction. It i moe ugged and equie le maintenance. Thi i widely ued in iolated wind powe geneation cheme. The magnetizing inductance value in an induction machine i a function of oto peed and i non linea []. Theefoe a ange of capacitance value i equied o that the machine i in excitation mode and the geneato teminal voltage i within the limit. The capacitance need to be tuned with vaying oto peed and loading condition, which i impactical due to intedependence of ytem vaiable, changing oto peed and the ytem nonlineaity. The capacitance value equied i uch that at a given oto peed; the geneated voltage in the tato winding doe not undego lage tanient. The induction geneato need to opeate moothly to give utained geneated voltage at the tato winding. Hence, the calculation of the capacitance value of the capacito bank i vey citical fo the deied opeation of the induction geneato. Roge, Shaaf and Elgammal [] peent the analytical d-q model to obtain maximum wind enegy captue. SEIG i modelled fom the tato ide with eigen value olution of the chaacteitic equation. Deign equation to decibe elf-excitation, lo of excitation and voltage egulation ae peented hee. Copyight to IJAREEIE 0.566/ijaeeie

2 ISSN (Online): (An ISO 397: 007 Cetified Oganization) R.C. Banal [3] give an oveview of the thee phae elf excited induction geneato, it claification and a detailed uvey of the liteatue on SEIG that dicue the poce of elf excitation and voltage build up, modelling, teady tate, and tanient analyi, eactive powe contol method, and paallel opeation. A calculation uing vaiou appoache ha been caied out to detemine the excitation capacitance fo a paticula ating of machine. Section II explain the voltage build up poce with the inceaing capacito cuent. Section III decibe the vaiou method involved in detemining the excitation capacitance. It futhe calculate the capacitance value uing Steady tate model Nodal Admittance Appoach and L C eonance pinciple fo the given ating of machine. Section IV conclude the capacitance value calculated fom diffeent appoache. II. SELF EXCITED INDUCTION GENERATOR: When an induction machine i diven by an extenal pime move at a peed geate than the ynchonou peed (negative lip) the diection of induced toque i eveed and it tat woking a an induction geneato. The eal powe flow out of the machine but the machine need the eactive powe. The main dawback of induction geneato in wind enegy conveion ytem application i it need fo leading eactive powe to build up the teminal voltage and to geneate electic powe. Uing teminal capacito aco geneato teminal can geneate thi leading eactive powe. Fo an iolated mode, thee mut be a uitable capacito bank connected aco the geneato teminal. Thi phenomenon i efeed to a capacito elf-excitation and the induction geneato i called a SEIG. A 3 phae elf excited induction geneato i a hown in Fig. (a): Fig. (a) elf excited induction geneato The voltage build up poce in an induction moto ha been explained in Fig. (b): Fig. (b) voltage build up in a 3ф induction geneato When the oto of induction machine i un at the equied peed, eidual magnetim peent in the oto ion geneate a mall teminal voltage o-a aco tato teminal. Thi voltage poduce a capacito cuent o-b. Thi cuent ceate a flux which aid the eidual flux, thu poducing moe flux and theefoe moe geneated voltage aco tato teminal epeented by b-c. Thi voltage end a cuent o-d in the capacito bank which eventually geneate voltage d-e. Thi cumulative poce of voltage build up continue till the atuation cuve of induction geneato inteect the capacito load line a hown by point f, thu giving a no-load geneated emf. The voltage build up depend upon the value of capacito. Highe the value of capacitance, geate i the voltage build up. The connection of a et of thee Copyight to IJAREEIE 0.566/ijaeeie

3 ISSN (Online): (An ISO 397: 007 Cetified Oganization) tatic condene aco the teminal of a 3ф induction moto eult in the addition of a contant leading component to the cuent taken. III. DETERMINATION OF EXCITATION CAPACITANCE: The voltage and fequency of an iolated elf-excited induction geneato (SEIG) ae not fixed and depend upon the geneato paamete and excitation capacitance. Hence it i neceay to detemine the ufficient value of the excitation capacitance. Vaiou appoache to detemine the capacitance equied to excite a elf-excited induction geneato have been epoted. Thee ae two appoache: Steady tate model (Pe Phae Equivalent Cicuit Appoach) Nodal Admittance Appoach Loop Impedance Appoach LC Reonance Pinciple Tanient model (d-q axi model appoach) The value of capacitance fo a thee-phae quiel cage induction geneato with pecification: 3Kw, 0/380V,.4/7.A, 4 pole, 50Hz, R =.Ω, R =.68Ω, L =L =9mH, L m =f (I m ), ha been calculated uing diffeent method. 3.. Nodal Admittance Appoach: Nodal admittance equation ae obtained fo the following equivalent cicuit [4] (Y m ) ( Y c ) (Y g ) Fig. 3 (a) Pe Phae Equivalent Cicuit of Self Excited Induction Geneato Feeding an Induction Moto Pump The nodal cuent equation i given a: V Y g + Y c + Y m = 0 () whee Y g i the total admittance of induction geneato. Y c i capacitive admittance and Y m i the total admittance of induction moto Y c = j a () X c Y g = Y g (Y g +Y g3 ) Y g +Y g +Y g3 (3) Y g = R g +jax g, Y g = jax mg, Y g3 = ar g a b +jax g (4) whee a i p.u fequency and b i p.u peed. Table : The vaiation of fequency with peed at bae peed = 500pm fo a 4 pole machine i given a: Copyight to IJAREEIE 0.566/ijaeeie

4 ISSN (Online): (An ISO 397: 007 Cetified Oganization) Speed (PU) Fequency (PU) Speed (PU) Fequency (PU) Fo calculation the p.u peed (b) i taken a 0.3 and the p.u fequency (a) a Y m = +jx M = +(XM ) X M +(XM ) (5) Unde teady tate elf excitation, Y m 0, theefoe Y g + Y c + Y m = 0. On olving the eal and imaginay tem we get R G R G +(XG ) +(XM ) = 0 (6) a X G X c R G +(XG ) X M +(XM ) = 0 The expeion fo a max on ubtituting = and X M =0 in equation (6), i given a (7) a max = b b b c b + R g Rg + X g X mg (8) Futhe ubtituting all the value, we obtain a max = whee b c = R g X m R g R g + X g X mg = (9) Subtituting = and X M = 0 in (7) give X c = a max X g + ax mg a b X g X mg +X g +R g a b X mg +X g +R g = (0) Thu C min = π50.x c = μf () C min i the minimum capacitance to povide the elf excitation. Pactically, teminal capacito C with a value lightly geate than C min hould be elected to povide elf excitation. 3.. L C Reonance Pinciple: A method baed on the combination of the pinciple of L-C eonance and non linea magnetization chaacteitic of the geneato i ued fom Fig. 3(b). [5] Fig. 3 (b) pe phae teady tate equivalent cicuit of SEIG Copyight to IJAREEIE 0.566/ijaeeie

5 ISSN (Online): (An ISO 397: 007 Cetified Oganization) The analyi i made by hot cicuiting the oto teminal and adding an excitation capacitance aco the tato teminal. Fig. 3 (c) pe phae equivalent cicuit of a SEIG at no load At no load the oto i conideed a an open cicuit and the L-C cicuit obtained in Fig. 3 (c) i ued to detemine the value of excitation capacitance. To geneate a voltage, the cicuit mut be at eonance. Theefoe, X c F = X l + X m () V g F = V F X m X l +X m (3) Synchonou peed tet eult ae obtained to find the elationhip between V g and X F m, whee V g i aigap voltage, F i p.u fequency and X m i the magnetiing eactance. The elationhip between V and X m i obtained a V F X m X l +X m = k 0 + k X m + k X m + k 3 X m 3 (4) Afte detemining the value of X m andx c, C can be obtained a C = ПfbF (X l +X m ) On ubtituting, fb = 50, F = and X l + X m = X = π 50 L a pecified above, the value of capacitance obtained i μF. IV. CONCLUSION: The quiel cage induction geneato due to it uggedne, low cot of contuction, le maintenance and uitability fo iolated opeation, i an inexpenive altenative to ynchonou geneato. Fo iolated geneation in emote aea a vaiable capacitance i equied to build up the voltage in an SEIG. Fo efficient conveion of wind enegy into electical enegy the induction geneato need to opeate moothly, giving utained geneated voltage at the tato teminal without any tanient. Theefoe, calculation of the capacitance value of the capacito bank i citical fo the deied opeation of the induction geneato. Thu the value of excitation capacitance equied ha been calculated. The cicuit uing LC eonance pinciple imply involve the detemination of oot of a polynomial without involving complex algebaic manipulation. The calculated value of C uing thi pinciple i μf. The nodal admittance appoach calculate the value of capacitance a μF. The pe phae equivalent cicuit model give the teady tate analyi but not the tanient analyi. (5) Copyight to IJAREEIE 0.566/ijaeeie

6 ISSN (Online): (An ISO 397: 007 Cetified Oganization) The calculated value of the excitation capacitance fo the given input paamete i tabulated below: Table : The calculated capacitance value: Reult (Calculated C Machine Input Paamete min ) L C Reonance Pinciple Nodal Admittance Appoach 3Kw, 0/380V,.4/7.A, 4 pole, 50Hz, R =.Ω, R =.68Ω, L =L =9mH, L m =7mH, p.u fequency a= and p.u peed b = μf μF Thu the value of capacitance equied fo elf excitation in an induction geneato ha been calculated uing Nodal admittance appoach and LC eonance pinciple. The Nodal admittance appoach give a lowe value of excitation capacitance. It equie geate and lengthy calculation a compaed to the othe method. REFERENCES [] Rajeh Kuma Thaku, Vivek Agawal, and Palui S. V. Nataaj, A eliable and accuate calculation of excitation capacitance value fo an induction geneato baed on inteval computation technique, IJAC Novembe 0, , DOI: 0.007/ [] Roge J. Vieia, A. M. Shaaf, Adel Elgammal, Deign of elf-excited induction geneato fo wind application, CCECE 0, IEEE. [3] R.C. Banal, Thee Phae Self Excited Induction Geneato: An Oveview, IEEE Tanaction on Enegy Conveion, Vol.0, No., June 005. [4] A. Abbou, M. Baaa, A. Ouchatti, M. Akheaz, and H. Mahmoudi, Capacitance equied analyi fo elf-excited induction geneato, JATIT, Vol.55 No.3, ISSN: , 30 th Sept., 03. [5] M.H. Haque, Detemination of excitation capacitance of a thee phae elf- excited induction geneato, IEEE, 0. Copyight to IJAREEIE 0.566/ijaeeie