Voltage Control of Standalone Photovoltaic System

Transcription

1 TERATOAL JOURAL f REEWABLE EERGY RESEARCH Seif Eddine Bukebbu et al., Vl.4,., 4 Vltage Cntrl f Standalne Phtvltaic Sytem Seif Eddine Bukebbu*, Meaud Khelif**, Djallel Kerdun* *Deartment f Electrtechnic, Faculty f Science and Technlgy, Labratry f Electrical Engineering f Cntantine (LGEC), Univerity Cntantine, Algeria. ** Renewable Energy Develment Center, CDER, Algier, Algeria. (bukebbu_eifeddine@htmail.fr, mkhelif@cder.dz, kerdjallel@yah.fr ) Crrending Authr; Seif Eddine Bukebbu, Deartment f Electrtechnic, Faculty f Science and Technlgy, Univerity Cntantine, Algeria, bukebbu_eifeddine@htmail.fr Received:.7.4 Acceted: Abtract- Thi aer reent a imle cntrl f a tandalne tvltaic ytem with lead-acid batterie trage. The bjective f thi ytem i t uly recribed active wer t tand-alne lad with crrectly wave ignal (current and vltage) in different atmeric cnditin. Thi reented wrk fcue n the trategy, which make it ible t enure the neceary wer fr the lad. Simulatin and exerimental reult illutrate the erfrmance btained. Keywrd- Phtvltaic anel, PVG, MPPT, battery, vltage cntrl, tand-alne tvltaic ytem. ntrductin With the decreae f cnventinal energy urce and the grwing rblem f envirnmental llutin, the reearch and utilizatin f the renewable energy, uch a lar energy, wind energy, ha been cncerned with mre and mre attentin [,]. PV wer i becming mre revalent a it ct i becming mre cmetitive with traditinal wer urce. Hwever, the utilizatin f dedicated energy trage ytem need t be taken int accunt becaue f the intermittent nature f the PV generatin. Energy trage ytem can en the ibility t emly renewable energy urce able t erate in tand-alne mde, grid-cnnected mde, and mde tranitin frm tand-alne t grid, r vice vera in micr-grid ytem [,]. By cmarin with the already exit wrk n tandalne tvltaic ytem [4, 5, 6]. n thi wrk we red a baic tand-alne tvltaic tatin with tw electrnic cnverter and batterie trage ytem, thi tructure i cntrlled t tracking the maximum wer int and t guarantee the neceary tandard vltage f the lad fr all cnditin; the active and reactive wer demanded by the lad i tranmitted in any eratin time. The ytem erfrmance i evaluated (imulatin and exerimentatin) in rigru ituatin t rve the feaibility and the imlicity f thi cntrl. n thi way, we can increae the wer generatin f tvltaic ytem and reduce the wer ct.. PVG Mdel and External Characteritic Simulatin Reult Starting frm the widely knwn tvltaic cell electrical equivalent circuit [7] (Fig. ), an equivalent mdel fr a mre werful PVG made f an ( x ) array f PV cell, i etablihed [8, 9]: Fig.. Simle mdel f the tvltaic cell = () D D exrein being deduced frm the emicnductr dide thery, the abve relatin may be detailed a: V + R V + R = (ex( ) ) () nkt / q R Where, i the light generated current (A), the PV cell aturatin current (A), q the electrn charge (q =, 6-9 C), h

2 TERATOAL JOURAL f REEWABLE EERGY RESEARCH Seif Eddine Bukebbu et al., Vl.4,., 4 K the Bltzmann cntant (k =, 8 - J/K), n the cell ideality factr, T the cell temerature. R h and R are ure araitic reitance characterizing reectively arallel current leakage and erie cnnecting circuit. n general, fr a PVG invlving an array f S cell cnnected in erie and P in arallel, it utut vltage current relatin may be deduced frm the baic cell equatin () a fllw [8] [9]: q( V + R ) V + R = (ex( ) ) () nkt Rh Frm equatin, an already temerature deendence f the cell external characteritic i etablihed. Furthermre, all the cell arameter (, n, R and R h ), are equally temerature related. Hwever, emicnductr dide thery, ugget that the mt ignificant temerature effect cme frm the revere aturatin current. Variatin f it value (T) with wrking temerature T, i uually evaluated relatively t it evaluated value (T r ) at a reference temerature T r [7]. ( ) qe T T g = ( ) ex[ ( )] (4) ( Tr ) Tr nk Tr T Where: Eg i the cell material band ga, ued here n temerature deendant, and K i the Bltzmann cntant. The value f aturatin current (T r ), may be evaluated thrugh the en circuit vltage V c (T r ) and the hrt circuit current SC (T r ) deduced frm (). c( Tr ) ( Tr ) = qvc ( Tr ) nkt ( e ) (5) The equatin f the illuminatin current brught back t the reference cnditin (G r = W/m², T r =5C ) i given a fllw: G = [ cc + t ( T Tr )] (6) G r t : Temerature cefficient f hrt-circuit current. G r : The reference illuminatin. G: The actually illuminatin. The recedent PVG mdel i imlemented in envirnment Matlab/Simulink a indicated in the (Fig. ). The main external reference characteritic f the PVG are etablihed uing the identified erturbatin inut (lar illuminatin, temerature) a arameter (Fig. 4, 5). PVG current (A) (A) V (V) PVG wer P (W) P(W) V (V) Fig.. PVG (current vltage) and (wer vltage) characteritic fr tandard cnditin (A) PVG current (A) G= 4 W/m G= 6 W/m G= 8 W/m G= W/m G= W/m V (V) PVG wer P (W) P(W) G= 4 W/m G= 6 W/m G= 8 W/m G= W/m G= W/m V (V) Fig. 4. PVG (current vltage) and (wer vltage) characteritic fr different lar illuminatin, T=5C PVG current (A) (A) t Vt PVG vltage V(V) PVG vltage V(V) T= - C T= C T= 5 C T= 5 C T= 7 C PVG wer P (W) P(W) Pmax Vt PPM PVG vltage V(V) PVG vltage V(V) T= - C T= C T= 5 C T= 5 C T= 7 C V (V) PVG vltage V(V) V (V) PVG vltage V(V) Fig.. Structure f the PVG Simulink mdel Fig. 5. PVG (current vltage) and (wer vltage) characteritic fr different temerature, G=W/m² 699

3 TERATOAL JOURAL f REEWABLE EERGY RESEARCH Seif Eddine Bukebbu et al., Vl.4,., 4. Strage Sytem One f the rincial diadvantage f lar energy i it intermittent character. Fr a ermanent ue, it i thu neceary t tre art f rduced energy. There are everal methd f trage: in water frm, hydrgen, a uercndenatr, r electrchemical battery [], [], []. The battery blck (Fig.6) imlement a generic dynamic mdel arameterized t rereent mt ular tye f rechargeable batterie (Lead-Acid, Lithium-n, ickel- Cadmium, and ickel-metal-hydride) []. - Phtvltaic anel (Tab.). - Mean f trage: (batterie). - DC/DC cnverter. 4- DC/AC cnverter allwing t feed the alternative lad, 5- Tranfrmer fr increaing the alternative vltage. Fig. 7. Tlgy f the tand-alne tvltaic ytem Fig. 6. Battery mdel [] The tvltaic anel ued in thi wrk i a UDTS5 tye (Fig. 8). The charge and dicharge equatin f the lead acid battery are given []: Charge: Q * Q Ebatt = E R. i K i K it + Ex( t) (7) it.q Q it Dicharge : Q * Ebatt = E R. i K ( it + i ) + Ex( t) (8) Q i t Ex ( t) = B. i( t).( Ex( t) + A. el( t)) (9) Where : Sel (t)= charge r dicharge mde. Ex(t)= exnentiel zne vltage (V). E batt = nn lenear vltage (V). V batt = battery vltage (V). E = battery cntant vltage (V). K = larizatin cntant (V/Ah) r larizatin reitance. Q = battery caacity (Ah). i t = actual battery charge (Ah). A = exnentiel zne amlitude (V). B = exnential zne time cntant invere (Ah) -. R = internal reitance (Ω). i = battery current (A). i * = filtered current (A). 4. Tlgy f the Stand-Alne Phtvltaic Sytem The autnmu tvltaic ytem cnit f (Fig. 7): Fig. 8. UDTS5 tvltaic anel Table.. UDTS5 Panel charecteritic Standard illuminatin G (W/m²) tandard Temerature T (C ) 5 Shrt-circuit current cc (A).4 Oen circuit vltage V c (V).8 Otimal vltage V t (V) 6.65 Maximum wer P max (W) 5.66 Frm Factr (%) 7 Outut (%) Serie reitr R (Ω).4 Cell urface S (cm²) * umber f the cell 6 7

4 TERATOAL JOURAL f REEWABLE EERGY RESEARCH Seif Eddine Bukebbu et al., Vl.4,., 4 The DC/DC cnverter i a bt cher cntrlled t extract the maximum wer frm the tvltaic anel fr different value f illuminatin and temerature. The inverter i cntrlled t maintain the utut vltage cntant fr any value f the lad, in thi rean a regulatin f the rectified average vltage f the inverter i made. The trage ytem cnit f (lead-acid) electrchemical batterie (V, 5Ah). 5. Cntrl Strategy The cntrl ytem i cmed f tw art, the cntrl f the bt cher and the three ae inverter. Due t it nnlinear external current vltage characteritic, the PVG maximum wer utut varie with it erating int. The latter being equally lad related, thi ccur even fr a given lar irradiatin and temerature. n thi cae nly a unique lad value may enure the timum erating int in term f maximum wer extractin frm the PVG, which utut vltage and current are then at their reective timal value (V t, t ). Generally, all the inut defining the timum erating int f the PVG (Slar irradiatin, temerature and lad, hading being a articular ituatin), are imed. Hwever, it i knwn in wer DC electrical circuit, that a witching DC-DC electrnic wer cnverter may be an efficient imedance adatr tl. Hence, it may be ued t adjut the equivalent lad imedance t the needed value fr PVG timal erating int, whatever are the lar irradiance, temerature and eventually hading rate [7]. The MPPT algrithm ued i a claical ne and will nt be detailed in thi aer. Fr the inverter, the cntrl i achieved t have a cntant alternating vltage fr any value f the lad; therefre a regulatin f the rectified average vltage i neceary (Fig. 9). By uing a three-ae rectifier with dide like a enr f the cntinuu vltage at the bundarie lad; the meaured vltage will be cmared with a reference cntinuu vltage crrending t the tandard nminal vltage neceary t feed the lad. The reult a ha thrugh a P regulatr and a haing circuit in rder t have finally the reference vltage f the inverter. 6. Simulatin reult During imulatin we ued 5 batterie (V, 5Ah) in erie, and an elevatr tranfrmer (Y/Y) (4/8V), cmmutatin frequency (f= khz), the imulatin reult btained are exed in (Fig. t Fig. 5). Simle vltage (V) Cntinuu vltage (V) Fig.. The inverter imle vltage Charge variatin Fig.. Cntinuu vltage 5 4 Lad current (A) Fig. 9. Cntrl circuit f the inverter Fig.. Current variatin fr different lad value 7

5 State f charge SOC (%) Batterie current (A) TERATOAL JOURAL f REEWABLE EERGY RESEARCH Seif Eddine Bukebbu et al., Vl.4,., 4 T enure the all real eratin ibilitie, a management ytem i neceary, becaue it i able t determine the erid and the duratin f each cae in rder t anwer the bjective f the alicatin Exerimental tet T validate the imulatin reult btained reviuly, we carried ut the aembly f (Fig. 6). The cntrl algrithm i imlemented uing the PC65E acquiitin card Batterie vltage (V) Fig.. Batterie current and tate f charge SOC Zm The PC-65E i an acquiitin card which belng t the 65E family f the natinal intrument firm; it can be directly cnnected t PC bu f a cmuter. Thi card i cmatible with MATLAB/SMULK tl envirnment, where it make it ible t aciate thi Sftware envirnment that hardware (material), thu it enrmuly facilitate the cntrl (a gd imulatin i enugh) where ne will gain ver the rgramming time [4] Senr nverter PC Card Cmuter Fig. 4. Batterie vltage 5 Rectifier Statin wer (W) 5 Tranfrmer Lad Fig. 6. Bench f the tand-alne tvltaic ytem ued 5 n exerimental tet we will hw the ecnd art f the tand-alne intallatin which i the vltage cntrl f the three-ae inverter with a variable lad. The imlified diagram f the intallatin carried ut i hwn in (Fig. 7). P Pbatt Plad Fig. 5. Stand-alne tvltaic wer During. and.4, the current are amlified becaue the lad wer are increaed, but the vltage delivered by the inverter remain cntant, fr all lad value the cntrl device alway kee the Uref value imed (Uref i elected accrding t the nminal vltage f lad eratin). The battery lad tate fllw the directin f the wer exchange, if the current i itive, the lad tate increae and the battery charge, and cnverely. The trage ytem make it ible t ulement the electric utut required fr the lad in the mment when the tvltaic wer i nt enugh, which will make it ible in all time t enure the intallatin ervice cntinuity. Fig. 7. Aembly ued 7

6 TERATOAL JOURAL f REEWABLE EERGY RESEARCH Seif Eddine Bukebbu et al., Vl.4,., 4 The exerimental reult btained are given in (Fig. 8 t Fig. ) with: V dc = V, = V, F= khz, lad 4 kva. n thee reult we are uing an inulatin interface with: Attenuatin cmed vltage i. Attenuatin cntinuu vltage V c i 5. Fr the current (A- V). V c V c lad nverter lad lad Lad variatin V dc variatin Fig.. Variatin f the lad and V dc vltage inv V inv lad V lad While we change the cntinuu vltage V dc f the inverter (V t 5V and 5V t V) (Fig. ) the cntrl alway kee the reference vltage with a mall tranitin tate in the variatin mment. Fig. 8. vltage and current variatin V c V c lad lad V c lad 8. Cncluin n thi aer, a imle cntrl f a tand-alne tvltaic tatin with lead-acid batterie trage ha been reented in rder t uly recribed active wer t tand-alne lad. A ecific vltage cntrl algrithm ued make it ible t enure the neceary tvltaic wer fr the lad and guarantee a cntant vltage inverter utut fr all lad value. The trage ytem make it ible t ulement the electric utut required by the lad in the mment when the tvltaic wer i nt ufficient, therefre the ervice cntinuity i enured in all time. The imulatin and exerimentatin reult btained f thi arach hw and cnfirm the reliability and the imlicity f thi tye f cntrl. Cncerning the future wrk in the field f tandalne PV ytem, thi tudy revealed that there i a need fr: Additin f the ver/under charging/dicharging battery trategy rtectin in the cntrl ytem. Management f the wer flux in all cmnent f tandalne PV ytem. Acknwledgment Fig. 9. reference vltage variatin When we aly a variable reference vltage t the cntrl device, the lad current fllw the directin f thi variatin, and the cntinuu vltage V c i cntrlled and will have the value f the reference vltage. When we increae r decreae the lad, the current value change becaue it i the lad which ime the current, but the inverter vltage value (in ur cae the rectified average vltage V c ) remain cntant at the reference. The authr exre their gratitude t Dr. T. Ghennam and Dj. Maizi frm the wer electrnic Labratry, military lytechnic chl, EMP, fr rviding them with electrnic material (inverter, enr ). Reference [] W. Cai, H. Ren, Y. Jia, M. Cai, X. Cheng, Analyi and imulatin fr grid-cnnected tvltaic ytem baed n Matlab, EEE, //$6.. [] M.C. Di Piazza, G. Vitale, Phtvltaic Surce, Mdeling and Emulatin, Bk, Sringer-Verlag Lndn. 7

7 TERATOAL JOURAL f REEWABLE EERGY RESEARCH Seif Eddine Bukebbu et al., Vl.4,., 4 [] S. M. Park, S. Y. Park, Pwer weakening cntrl f the tvltaic- battery ytem fr eamle energy tranfer in micrgrid, EEE //$.. [4] A. aik, R.Y. Udaykumar, K. Vinayak, Pwer management f a hybrid PEMFC-PV and Ultracaacitr fr tand-alne and grid cnnected alicatin, EEE nternatinal Cnference n Pwer Electrnic, Drive and Energy Sytem, December6-9,, Bengaluru, ndia. [5] H.K. Davijani, O. Olrunfemi, Mdeling and Steady- State Analyi f a Stand-Alne, Phtvltaic-Three Phae nverter Pwer Sytem, EEE //$6.. [6] H. Mahmd, D. Michaeln, J.Jiang, Cntrl Strategy fr a Standalne PV/Battery Hybrid Sytem, EEE //$.. [7] M. Khelif, A. M raui, A. Malek Simulatin, timizatin and erfrmance analyi f an analg, eay t imlement, erturb and berve MPPT technique t be ued in a.5 kw tvltaic ytem RSEC, OUARZAZATE, March 7-9,. [8] L.T. Huan, C.T. Siang, Y.J. Su, Develment f Generalized Phtvltaic Mdel Uing Matlab/ Simulink, Prceeding f the Wrld Cngre n Engineering and Cmuter Science 8 WCECS, Octber - 4, San Francic, USA8. [9] M. Francic, G. Lngatt, Mdel f Phtvltaic Mdule in Matlab d cngre iberamerican de etudiante de ingeniería eléctrica, electrónica y cmutación (ii cibelec 5). [] A.T. SGO, Sytème d alimentatin tvltaïque avec tckage hybride ur l habitat énergétiquement autnme, Dctrate thei, Henri Pincare Univerity, ancy-, Feb.. [] H. Fakham, D. Lu, B. Franci, Pwer Cntrl Deign f a battery charger in a Hybrid Active PV generatr fr lad fllwing alicatin, EEE Tranactin n ndutrial Electrnic, Vl. 58,., , Jan., TE-9-7. [] X.Liu, P. Wang, P. C. Lh, F. Ga, F. H. Ch, Cntrl f Hybrid Battery/Ultra-caacitr Energy Strage fr Stand-alne Phtvltaic Sytem, EEE //$6.. [] O. Tremblay, L.A. Deaint, Exerimental Validatin f a Battery Dynamic Mdel fr EV Alicatin, Wrld Electric Vehicle Jurnal Vl. - SS AVERE. [4] Webite: 74