JJMIE Jordan Journal of Mechanical and Industrial Engineering

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1 JJMIE Jordan Journal of Mechancal and Industral Enneern olume 4, Numer 1, Jan ISSN Paes Study and Control of a Power Electronc Cascade usn Photovoltac Cell-Multlevel Inverter Dalla Berer a Adelazz Talha a Fard Bouchafaa a Mohamed Sehr Bouchert a Laoratore d Instrumentaton, F.E.I, Unversté des Scences et de la Technoloe Houar Boumedene, Aler, ALGÉRIE Laoratore de Commande des Processus, École Natonale Polyechnque, Aler, ALGÉRIE Astract In ths paper, we study the performances of the cascade of the photovoltac cell wth the multlevel neutral pont clamped (NPC) voltae source nverter (SI). In the frst part, we remnd the model of the doule stator nducton motors (DSIM). Then, we develop knowlede and control models of ths nverter usn the connecton functons of the sem-conductors. After that, we propose a PWM stratey to control ths converter. In ths part, the nverter s fed y constant nput DC voltaes. In the last part, we study the performances of the consttuted y two photovoltac cells two three-level NPC SI - DSIM. The results otaned confrm the ood performances of the proposed cascade Internatonal Conference and Exhton on Green Enery & Sustanalty for Ard Reons & Medterranean Countres All rhts reserved Keywords: Multlevel nverter; Generator Cells; Photovoltac; Control; DSIM. 1. Introducton * Nowadays, the man enery suppler of the worldwde economy s fossl fuel. Ths, however has led to many prolems such as loal warmn and ar polluton. Therefore, wth reard to the worldwde trend of reen enery, solar power technoloy has ecome one of the most promsn enery resources. The numer of P nstallatons has had an exponental rowth [1]. One of the most mportant types of P nstallaton s the rd connected nverter confuratons. These rd connected P systems can e cateorzed from two vewponts: P cell and nverter confuratons. The P cell arranements fall nto four road roups: centralzed technoloy, strn technoloy, mult-strn technoloy and AC-module and AC-cell technoloes [2]. All approaches have advantaes and dsadvantaes [2], [3]; and wll compromse varous attrutes such as harmonc eneraton, complexty, effcency, flexlty, relalty, safety, modularty and cost. However, for resdental P nstallatons, the most sutale confuraton seems to e the strn or multstrn technoloes where one or more strns of P cells are connected to a snle nverter. Usn ths type of confuraton, there wll e no losses assocated wth the strn dodes compared to centralzed technoloy. Moreover, ndependent Maxmum Power Pont Trackn (MPPT) s possle for all strns whch mht e nstalled n dfferent szes and orentatons. Correspondn Author. derer@yahoo.fr Ths also ncreases the overall effcency under specal crcumstances lke partal shadown. There are dfferent approaches to mplement strn and mult-strn topoloes. Usually, these modules consst of a solar array and a DC to DC converter controlled y a MPPT alorthm. Afterwards, the outputs of the DC/DC converters uld up a DC voltae whch s then converted to AC y means of an nverter [4]. The other posslty s to use multlevel. P systems cateorzed y dfferent P cell confuratons and nverter types topoloes whch are ale to enerate etter output qualty, whle operatn at lower swtchn frequency. Ths mples lower swtchn dsspaton and hher effcency. Moreover, ths topoloy utlzes swtches wth lower reakdown voltae; therefore, t can e used n hher power applcatons at lower cost. It s worth mentonn that althouh the numer of swtches n ths approach s hher than other two level topoloes, for a suffcent hh numer of levels, the output flter can e avoded whch means less weht, cost and space. On the other hand, even wth the same sze of flter at the output, the swtchn frequency can e decreased whch means hher effcency. In eneral, a reater numer of swtches n multlevel converters can e justfed snce the semconductor cost decreases at a much reater rate than the flter components cost. Ths project the total cost of multlevel converters to e comparale or even lower than that of two-level converters. Ths paper presents the performances of the cascade of the photovoltac cells wth the multlevel NPC nverter. Smulaton results otaned confrm the ood performance of the proposed cascade.

2 Jordan Journal of Mechancal and Industral Enneern. All rhts reserved - olume 4, Numer 1 (ISSN ) 2. Model of the DSIM The model of the doule stator nducton machnes (DSIM) s ven n fure1 [5], [6]. Fure 2. Representaton of DSIM n the Park frame 3. Modelln of Three Level NPC SI 3.1. The three-level NPC SI structure The three-level NPC SI s consttuted y three arms and two DC voltae sources [9], [10]. Every arm has four drectonal swtches n seres and two dodes (Fure3) [7]. Fure 1. DSIM schema Park model of the DSIM, wth P pars of poles, s defned y the follown equatons system [7], [8]: sd sq sd sq rd rq dφsd1 1rs1 sd1 ωφsq dφsq1 1rs 1sq1 ωφsd dφsd 2 2 rs 2sd 2 ωφ dφsq 2 2 rs 2sq 2 ωφ dφrd rr rd ωlφrq dφrq rr rq ωlφrd 1 1 sq 2 sd 2 The electromanetc torque s ven y the follown expresson: Fure 3. The three-level NPC nverter C em m r Lm p rd L L sq1 sq2 rq sd1 sd 2 The model of the DSIM n the Park frame s ven y fure2.

3 2010 Jordan Journal of Mechancal and Industral Enneern. All rhts reserved - olume 4, Numer 1 (ISSN ) Knowlede model The swtch connecton functon F ks ndcates the opened or closed state of the swtch TD ks. We defne two a half arm connecton functon F km wth: k : arm 0 for the lower half arm numer m 1 for the upper half arm For an arm k of the three-phase three-level NPC, several complementary laws controls are possle. The control law whch lets an optmal control of ths nverter s: B B K 4 B K 1 B K 3 K 2 Ths stratey s characterzed y two parameters [8], [11]: - The modulaton ndex m s defned as a rato etween the carrer frequen cy f p and the reference voltae frequency f: m f p f - The modulaton rate r s the rato etween the mantude m of the reference voltae and three tmes of the carrer s mantude: U pm : r m U pm Fure4 shows the snals of ths stratey. Where B Ks represents the ate control of the swtch Tks. We defne the half arm connecton functon F1 and F 0 assocated respectvely to the upper and lower half arms. Where s arm numer (=1, 2, 3). F 11 F11F12 F21 F21F22 F31 F31F32 ; ; F10 F13F14 F20 F23F24 F30 F33F34 Fure 4. Space vector modulaton stratey The output voltaes of the nverter relatvely to the mddle pont M are defned as follows: AM BM CM F F F U C 1 F F F U C 2 Ths system shows that the three-level can e consdered as two two-level voltae source nverters n seres. Ths characterstc lets us to extrapolate the stratees used The nput currents of the nverter are ven as follow d 1 F111 F212 F313 F F F d The current d0 s defned y the follown relaton: d d1 d 2 4. PWM Stratey of the Fve Level NPC SI Fure 5. Smple voltae of the nverter and ts spectrum Fundamental mantude (P.U) Harmoncs rate 0.2 r Fure 6 The adjustn characterstc of the output voltae of the nverter The nverter s controlled y the space vector modulaton stratey whch uses two polar carrers.

4 Jordan Journal of Mechancal and Industral Enneern. All rhts reserved - olume 4, Numer 1 (ISSN ) For even values of m, the output voltaes present symmetry relatvely to the quarter of the perod. Then, only odd harmoncs exst. These harmoncs ather y famles centred around frequences multple of 4mf. The frst famly centred around frequency 2mf s the most mportant n vew of ts mantude (Fure5). The modulaton rate r lets lnear adjustn of fundamental mantude from r 0 to r max 1,15 (Fure6). The harmoncs rate decreases when r ncreases (Fure6). Fure 8. Electrcal Scheme of a photovoltac cell wth one dode To smulate a P array, a P smulaton model whch was otaned usn Matla/Smulnk, was used ased on the follown equaton: I I Rs, I [exp q AkN T 1 ph, Is, ] s, ms R sh, where I s the P array output current (A); the P array output voltae (); Iph s the photocurrent depends on the solar radaton and the cell temperature; Is s the cell reverse saturaton current vares wth temperature; Rs s the seres resstance; Rsh s the shunt resstance, q s the 19 chare of electron = C; K s the Boltzmanns constant K= J/K; A s the pn juncton dealty factor; T s the cell temperature (K) and s the ap. In our case, we have used photovoltac enerator MSX- 83 composed y 36 cells n en seres. The characterstcs of a P cell of chanes n current and power ased on the voltae of the P cell s shown n fures 9 and 10(for a temperature T=25 and lht E=1000W/m 2 ). R I Fure 7. Two photovoltac enerator-flter-two three-level NPC SI-DSIM cascade 5. Cascade of two Photovoltac Generator two Three- Level NPC SI - DSIM Untl now, we have supposed the nput DC voltaes of the three-level NPC SI constants. In ths part, the authors study a eneraton nput DC voltae technque. For ths, we propose a cascade consttuted y two photovoltac enerator-two three-level NPC SI whch feeds a DSIM (Fure7) Modelln of Photovoltac Generator The uldn lock of the P array s the solar cell, whch s ascally a p n semconductor juncton that drectly converts lht enery nto electrcty. Snce the nventon of solar cells, several models have een proposed to descre ts functon and ehavor under dfferent weather condtons (lht and temperature) [12]. In ths paper, we present the model wth one exponental (dode) [13], [14]. The equvalent crcut s shown n fure8. Fure 9. Current voltae Characterstc P Fure 10. Power voltae Characterstc P

5 2010 Jordan Journal of Mechancal and Industral Enneern. All rhts reserved - olume 4, Numer 1 (ISSN ) Modelln of Intermedates Flters The model of these flters s defned y the system: C C K 1 K 2 du du CK 1 CK 2 I I pvk pvk I I dk 1 dk 2 K: Numer of the ntermedate flters (K=1, 2). follown We note that the currents d11 and d21 are respectvely the opposte of the currents d12 and d22. The currents d10 and d20 have a mean value practcally null (Fure11). The output voltaes of nverter a1 and a2 are practcally snusodal (Fure12). The performance of the speed control alorthm of the DSIM shows that the current of the machne nearly s snusodal; the speed follows quetly ts reference. The speed and the torque effect for the chare varaton etween two nstants t=1.5s and t=2.5s (Fure13). 6. Conclusons 5.3. Smulaton Results The parameters of the ntermedate flter C 11 =C 12 =C 21 =C 22 =10mf. are: After a ref ntroducton of dfferent possle choces for nverters n Photovoltac applcatons, t s shown that the Cascaded Multlevel Converter s a sutale choce for P systems. The paper presents the performance of the cascade of the photovoltac cell wth the multlevel nverter. The smulaton results show that the performances otaned wth ths cascade are full of promse to e usn ths nverter n renewale enery. References Fure11. Input currents of the two three-level nverter Fure 12. Output voltae of two three level nverter Fure 13. The DSIM performances [1] F. Blaajer, R. Teodorescu, M. Lserre, and A.. Tmus, "Overvew of control and rd synchronzaton for dstruted power eneraton systems", IEEE Transactons on Industral Electroncs, vol. 53 No. 5, 2006, [2] S. B. Kjaer, J. K. Pedersen, and F. Blaajer, "A revew of snle-phase rd-connected nverters for photovoltac modules", IEEE Transactons on Industry Applcatons, ol. 41, No. 5, 2005, [3] Y. Xue, L. Chan, S. B. Kjaer, J. Bordonau, and T. Shmzu, "Topoloes of snle-phase nverters for small dstruted power enerators: an overvew", IEEE Transactons on Power Electroncs, ol. 19 No. 5, 2004, [4] G. Walker and P. Serna, "Cascaded DC/DC converter connecton of photovoltac modules", IEEE Transactons on Power Electroncs, ol. 19 No. 4, 2004, pp [5] D. Hadouche, H. Razk and A. Rezzou, "Study and smulaton of space vector PWM control of doule-star nducton motors", IEEE-CIEP 2000, Acapulco, Mexco, 2000, [6] A. Mont, A. P. Morando, L. Resta and M. Rva, "Comparn two level GTO-nverter feedn a doule-stator asynchronous motor wth a three level GTO-nverter feedn a snle star asynchronous motor", EPE 1995, Sevlla, Span, 1995, [7] D. Berer, M. Berkouk, A. Talha and M. O. Mahmoud, "Study and Control of Two Two - Level PWM Rectfers Clampn Brde Two Three Level NPC SI Cascade. Applcaton to Doule Stator Inducton Machne", IEEE 35th Power Electroncs Specalsts Conference, PESC 2004, Aachen, Germany, 2004, [8] A.Talha, D.Berer and M.S.Bouchert, "Lnear Feedack Control of Mult DC Bus Lnk oltaes of Multlevel NPC SI Cascade", 14th IEEE Internatonal Conference on Electroncs, Crcuts and Systems ICECS 2007, Marrakech, Morocco, Decemer 11-14, 2007,

6 Jordan Journal of Mechancal and Industral Enneern. All rhts reserved - olume 4, Numer 1 (ISSN ) [9] J. Rodruez, J. La, and F. Pen, "Multlevel nverters: A survey of topoloes, controls, and applcatons", IEEE Transactons on Industral Electroncs, ol. 49, No. 4, 2002, [10] S. Alepuz, S. Busquets-Mone, J. Bordonau, J. Gao, D. Gonzalez, and J. Balcells, "Interfacn renewale enery sources to the utlty rd usn a three-level nverter", IEEE Transactons on Industral Electroncs, ol. 53, No. 5, 2006, [11] L.M. Tolert, F.Z. Pen and T.G. Haelter, "Multlevel PWM methods at Low Modulaton ndces", n Proceedns of 1999 Appled Power Electroncs Conference and exposton (APEC), 1999, [12] M. Bayean, "Power electronc technoloes for dstruted Power", Keynote paper, 9th European conference on Power Electroncs and Applcatons, EPE 01, 27th Auust 2001, Graz, Austra, [13] B.Multon and al, "Analyss and Expermental aldaton of arous Photovoltac System Models", 7th Internatonal ELECTRIMACS 2002 Conress, Montréal, Canada, 2002, 1-6. [14] E. Massada, "Power Converter for Renewale and Dstruted Sources", 9th Internatonal Conference on Power Electroncs and Moton Controls, EPE-PEMC 2000, Kosce, Slovak Repulc, 2000.