IMPROVEMENT OF THE QUALITY OF ELECTRICAL POWER BY A PHOTOVOLTAIC GENERATOR CONNECTED TO THE GRID

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1 Rev. Roum. Sc. Techn. Électrotechn. et Énerg. Vol. 61, 1, pp. 7 41, ucrest, 216 IMPROVEMENT OF THE QULITY OF ELECTRICL POWER Y PHOTOVOLTIC GENERTOR CONNECTED TO THE GRID SID HMED TDJER 1, IDIR HI Key words: ctve flters, Power qulty, Photovoltc genertor, Hrmoncs nlyss. The pper presents new rchtecture of ctve flterng, n whch photovoltc genertor s used s current source. Ths genertor compenstes hrmonc dstorton nd rectve power. Unlke the clsscl ctve flter tht uses cpctor, the proposed system cn generte power to the grd when there s n excess of power t the photovoltc genertor level. 1. INTRODUCTION In the lst recent yers, there s shrp ncrese n connectng non-lner lod to the grd utlty, such s: computers, fx mchnes, dschrge lmps, rc furnces, ttery chrgers, nverters. Indeed, n power grd, nonlner lod sors non-snusodl current. Tht cn e resolved to fundmentl nd hrmoncs. The ojectve s to oth lmt the hrmonc nd rectve currents usng n dentfcton method for estmtng ts dsturnce, nd to mprove the qulty of electrcl power. 2. INTERPRETTION OF HRMONICS The hrmonc concept s ntroduced n the erly 19 th century y Joseph Fourer showed tht ny non-snusodl perodc sgnl my e represented y seres, or sum of snusods of dscrete frequences. ( t) = Y ( 2 yh sn( h ωt ϕh )) h= 1 y, (1) where: zero component Y of sd Fourer seres s the dc component, the frst component (h = 1) s clled the fundmentl component. y h s RMS vlue of the hrmonc component of order h. ϕ s the phse shft of the hrmonc h. h. PROLEM OF HRMONIC CURRENTS ND FILTERS The qulty of electrcl energy cn e dsrupted, whch my cuse mlfuncton of devces connected to the grd. It s necessry to develop flterng systems tht cn mprove the qulty of energy. Inverters for photovoltc systems hve the potentl to perform ths flterng functon [1]. s llustrted n Fg. 1, the prolem of the hrmonc dstorton ppers even f the supply voltge t pont s purely snusodl, the voltge drop due to the lne mpednce (Z L1 Z L2 ) cuses dsrupton of the voltge t pont. Ths voltge dstorton n turn nfluences other lods connected to pont, t s the mn mpct of the hrmonc currents whch re looped on the voltges t connectng nodes. n mportnt crteron of qulty ssessement s the totl hrmonc dstorton of current (THD) [2]. Z L1 Z L2 Other lods Fg. 1 The hrmonc propgton grds. Sources of hrmonc currents 2 ( I) h= 2 h THD =, (2) I f where I f s the current fundmentl. Reducng hrmonc currents n the grd of the perred flow pths whch vod ths current grd s often ntroduced. Ths soluton s known s the hrmonc flter. In prctce, there re two types of flters: pssve nd ctve flters..1. PSSIVE FILTERING The prncple of pssve flterng s to loclly modfy the mpednce of the grd to dvert the hrmonc currents nd, t the sme tme elmnte the resultng hrmonc voltges. These flters consst of cpctve nd nductve elements whch re rrnged so s to otn seres resonnce t predetermned frequency. To desgn ths type of flter, precse knowledge of the chrcterstcs nd ehvor of the grd under the effect of hrmoncs s requred. Such desgn requrement s generlly stsfed wth smulton softwre. These devces my hve mny drwcks, mong lck of flexlty to dpt to chnges n the lod chrcterstcs. Moreover, the effectveness depends on the mpednce of the grd tht s unknown nd my vry. Ther nlty to cover wde frequency nd, where the use of multple flters of dfferent rnk greement, must e used..2. CTIVE FILTERING Two mn resons led to desgn new structure of modern nd effcent flter clled ctve flter. The frst reson s due to the nherent drwcks of trdtonl remedton solutons tht no longer respond to chngng lods nd electrcl grds []. 1 Unversty of oumerdes, Electrfcton of Industrl Enterprses Lortory, F.H.C., 1 v. de l Independnce, oumerdes, lger, E-ml: sdhmed79dz@yhoo.fr.

2 8 Sd hmed Tdjer, Idr H 2 The second reson dels wth the emergence of new semconductor devces, such s gte turn off (GTO) nd nsulted gte polr trnsstor (IGT). The purpose of these flters s to generte ether current or voltge hrmoncs to compenste dsturnces whch re responsle for the de-grdton of electrcl equpment nd nstlltons. Three possle topologes (Fg. 2) of ctve flters cn e employed [4, ]: seres ctve flter: desgned to compenste voltge dsturnces such s hrmoncs, mlnces nd voltge dps; prllel ctve flter: desgned to compenste ll power dsturnces such s hrmoncs, mlnces nd rectve power; prllel-seres ctve flter: unversl soluton to offset ny dsrupton n current nd voltge. c Fg. 2 ) Seres ctve flter; ) Prllel ctve flter; c) Prllel-seres flter. c1 cα cd Low Pss flter ĩ cd ĩ cd 1 c2 c cβ Low Pss flter C P(ωt) C T P T (ωt) c ĩ ĩ c 2 Dα nd Dβ.. IDENTIFICTION METHODS OF HRMONIC CURRENTS The qulty nd performnce of hrmonc currents compenston re strongly dependent on the performnce of the dentfcton stge n control lock. Severl dentfcton methods were proposed n the lterture [6]. new method of dentfyng current erences sed on the orthogonl components of qudrtc enchmrks pproch, αβ nd DQ [7, 8] under the nme two-phse method s proposed. Ths pproch requres fewer clcultons nd genertes currents wthout ntroducng the nstntneous power erence clcultons [9]. sn( ωt c1() t c2() t = I1sn( ωt α1 ) c() t sn( ωt α1 sn( nωt ) I sn( ), n 2... N n nωt α = n sn( nωt Fg. The generl structure of the method of two-phse flows. () The prncple of ths method s sed on the decomposton of lod to current fundmentl component nd hrmoncs. The dstorted three phse current cn e wrtten s the fund-mentl plus the hrmoncs, s gven elow: sn( ωt c1() t c2() t = I1sn( ωt α1 ) c() t sn( ωt α1 sn( nωt ) I sn( ), n 2... N n nωt α = n sn( nωt () where c1( t), c2 ( t), c( t) re the nstntneous currents sored y the lod. The frst prt represents the fundmentl current nd the second s the sum of currents. Fgure llustrtes the dentfcton method of the twophse current locks [7]. Estlshng the qudrtc decomposton n the αβ erence, the trnsfer mtrx of Concord C gves the currents cα, cβ, c. fter seprton of the fundmentl from hrmoncs, one cn wrte the followng smplfed equton : cα sn( ωt I = 1 cβ 2 cos( ωt α1) sn( nωt ) I, n= 2... N n cos( nωt ) (4) cos( ωt) sn( ωt) wth P ( ωt) =. sn( ωt) cos( ωt) () P( ωt) s Prk trnsformton, cd : curents n DQ xes. Components representng the erence currents,, must e njected n phse opposton to the 1 2 electrcl grd y the prllel ctve flter. They re clculted s shown n the followng equton: 1 2 T T cd = ω C 2P ( t). (6) Severl cses of compenston for hrmonc nd rectve dsturnces re possle. Tle 1 shows the dfferent control prmeters.

3 Photovoltc genertor connected to the grd 9 Tle 1 The methods of compenston of the two-phse currents method Compenston mode Control prmeters Hrmonc compenston cd = cd ; c = c Rectve compenston cd = ; cd = Overll compenston cd = cd ; cd = To fnd the hrmonc currents n the phse mrker we successvely perform C T 2, P T trnsformton. Note tht the nverse mtrces trnsfer of Concord nd Prk trnsformtons re s elow: 1 1 T 2 C 2 = 2 2 (7) nd T cos( ωt) sn( ωt) P ( ωt) =. (8) sn( ωt) cos( ωt) Grd voltges (V sk ) Impednces (Z cck ) Injected currents (I njk ) Flter L f R f T 1 T 2 T G=1 W/m² T=2 C V s V s2 V s1 V PV - DC-DC PV T 4 T T 6 ck To polluton lod The prllel ctve flter Fg. 4 Hrmonc compenston system photovoltc genertor. To the grd Consumer 1 Consumer 1 V 22/11 V Rectfer 1 mh Ω Consumer 2.2 mf Fg. ) The three-phse lod; ) electrcl dgrm of phse. 4. PROPOSED PHOTOVOLTIC SYSTEM FILTER, RESULTS ND DISCUSSIONS The glol model of the structure ws used to study the functonl vldty of the prllel ctve flter (Fg. 4) through severl smultons [1 12]. Dfferent smultons hve een crred out, to perform the followng studes [9, 1]: hrmoncs nd rectve power compenston; full compenston nd the trnsfer of the excess energy to the grd DESCRIPTION OF THE NONLINER LOD The non-lner lod conssts of three ndependent sngle phse consumers suppled through trnsformer, ech of whch contns non-lner lod. Ths chrge consumes current hvng very strong hrmonc content (Fg. ). The lod s suppled y three-phse lnced nd effectve voltge 22 V system. The three-phse current drwn y the lod s shown n Fg FIRST CSE: COMPENSTION HRMONICS ONLY The frst cse consdered s the compenston of the hrmoncs, controllng the photovoltc genertor s mde so s to generte current hrmoncs only. The erence current for compenstng hrmoncs only dentfed y the method of two-phse current s shown n the followng Fg. 7. The spectrl presentton of grd current consumpton fter hrmonc compenston s gven n Fg. 7c. The overll THD whch ws 17.4 % n Fg. 6c s reduced to vlue of 1.6 %. 4.. SECOND CSE: COMPENSTION OF HRMONICS ND RECTIVE COMPONENT In ths secton, the compenston of hrmonc currents nd consumed rectve power s nvestgted. In the frst cse, the compensted current s snusodl ut t s not n phse wth the voltge of the grd (Fg. 8). Whle n the second cse, the compensted current s snusodl nd n phse wth the supply voltge of the grd tht shows the compenston of

4 4 Sd hmed Tdjer, Idr H 4 the rectve prt (Fg. 8). The photovoltc genertor responds well to the current reproducton erence wth smll fluctutons round THIRD CSE: CTIVE POWER, RECTIVE ND PPRENT In the sence of the photovoltc genertor, the lod consumes the followng powers P = 1 W, Q = 47 vr gvng n pprent power S = 18 V. Fgure 9 shows the powers P, Q nd S efore connectng the PV genertor. Wth compenston of hrmoncs nd rectve power crcultng n the grd s zero. In ths cse, the pprent power S s equl to the ctve power P (Fg. 9). In the cse of vllty of ddtonl power to the power requred to compenste hrmoncs nd rectve, one cn control the ctve flter to send the power to the grd recevng supply of ctve energy (Fg. 1). In ths cse the current wll e n phse opposton wth the mns voltge s shown n the followng Fg. (Fg. 1) c1, r2, c () ) Fg. 6 ) Instntneous currents sored y the lod; ) lod current; c) hrmonc spectrum c1. Fg. 7 ) Three-phse erence current; ) compenston current; c) hrmonc spectrum of current fter compenston. 2 1 Cse1:Wtout rectve compenston 2 1 Cse 2 er 2: cs Wth : the compenston de rectve l prte compenston réctve comp1(), Vs1 (V) - -1 comp1(), Vs1 (V) Fg. 8 ) Current nd voltge wthout rectve compenston; ) current nd voltge wth the rectve compenston

5 Photovoltc genertor connected to the grd S(V), P(W), Q(vr) S(V) P(W) P(W) Q(vr) S(V), P(W), Q(vr) S(V) P(W) Q(vr) Fg. 9 ) Powers efore connectng the PV; ) powers wth compenston of hrmoncs nd rectve. S(V), P(W), Q(vr) S(V) Q(vr) P(W) Current (), Voltge (V) Current suppled to the network Supply voltge Fg. 1 ) Powers P, Q nd S n cse of surplus of energy vlle; ) grd current cse of surplus of energy.. CONCLUSION In ths pper, new system hrmonc compenston usng photovoltc genertor s soluton to polluton electrc grds hs een proposed. For vldton, smulton frmework hs een developed for dfferent cse studes. The temporl nd spectrl nlyss of the lod current nd power fctor demonstrte good compenston of hrmoncs nd rectve power. good lne current fter compenston wth THD = 1.6 % hs een cheved. lso n the cse of vllty of energy t the photovoltc genertor termnls, the system cn send ths excess of energy to the grd. Receved on Septemer 6, 214 REFERENCES 1. J. S. Sujk Jr., J. Mcqulkn, Hrmoncs-cuses, effects, mesurements, nlyss, nd updte, IEEE Trns. Ind. pplct., 26, pp , H. kg, ctve Hrmonc Flters, Proc. of IEEE, 9, 12, pp , 2.. G. T. Heydt, Electrc Power Qulty, West Lfyette, n: Strs n Crcle, M.. lll, Contruton to the Study of ctve Compenstng Lowvoltge Electrcl, PhD Thess ULP Strsourg, 22.. S. Chenn, Three-level neutrl pont clmped shunt ctve power flter performnces usng ntellgent controllers, Rev. Roum. Sc. Techn. Électrotechn. et Énerg., 9,, pp. 1, F. D. Frejedo et l., Novel Hrmonc Identfcton lgorthm sed on Fourer Correlton nd Movng verge Flterng, IEEE, pp , D. Oulddeslm, Technque neurommétques pour l commnde dns les systems électrques: pplcton u fltrge ctf prllèle dns les réseux électrques sse tenson, PhD Thess Hute lsce, D. Zhng, Z.P. Jng, n dentfcton method of lod hrmonc current sed on P neurl Network, Proc. IEEE, 2, Chn, pp. 27 1, S. Tdjer et l., Hrmoncs Compenston System sed on Photovoltc Genertor, Interntonl Symposum on Power Electroncs, Electrcl Drves, utomton nd Moton, Proc. IEEE, Sorrent, Itly, pp , H. ell, Y. Rmdn, F. Mouly, K. Medles, Irrdnce nd Temperture Impct on Photovoltc Power y Desgn of Experments, Rev. Roum. Sc. Techn. Électrotechn. et Énerg., 8,, pp , R. eld, Hddouche,. Htt, M. Lrf, Shunt ctve power flter connected to photovoltc rry for compenstng hrmonc nd rectve power smultneosly, Proc. IEEE, Turkey, pp , S. Tdjer, Etude d un système de compenston d hrmonque en utlsnt un générteur photovoltïque, Mgster Memory Unversty M Hmed ougr (oumerdes), P. Ynn, Study of the Integrton of Dstruted Generton n Network sed on. pplcton to the PV Genertor, PHD n Electrcl nd Electronc utomtc. Ntonl Center for technologcl reserch, Frnce, 24.