Micro-Grid Simulation during Grid-Connected and Islanded Modes of Operation

Transcription

1 Mico-Gid Siulation duing Gid-Connected and Ilanded Mode of Opeation F. D. Kanello, A. I. ouchnika, N. D. Hatziagyiou, Senio Mebe, IEEE Abtact echnology evolution, envionental concen aociated with cental electic powe plant and deegulation of the electic utility induty ae poviding the oppotunity fo all ditibuted geneato to becoe vey ipotant in ode to atify the on ite cutoe expanding powe deand. In thi pape, the teady tate and tanient opeation of a typical icogid ae tudied. he odel of two dipeed geneation unit (photovoltaic yte, wind tubine) ae peented. Model of the powe electonic inteface and contol tategie fo fat contol of fequency and voltage agnitude without counication ae deived. Keywod: icogid, odeling, dipeed geneation, wind tubine, photovoltaic yte, contol, ilanding, powe electonic inteface. I. INRODUCION ICROGRIDS copie low voltage ditibution yte M with ditibuted enegy eouce, uch a photovoltaic powe yte and wind tubine, togethe with toage device. hee yte ae inteconnected to the ediu voltage ditibution netwok, but they can be alo opeated iolated fo the ain gid. Fo the cutoe point of view, icogid povide both theal and electicity need and in addition enhance local eliability, educe eiion, ipove powe quality by uppoting voltage and educing voltage dip and potentially lowe cot of enegy upply. Fo the utility point of view, application of ditibuted enegy ouce can potentially educe the deand fo ditibution and taniion facilitie. Clealy, ditibuted geneation located cloe to load will educe flow in taniion and ditibution cicuit with two ipotant effect: lo eduction and ability to potentially ubtitute fo netwok aet. Futheoe, the peence of geneation cloe to deand could inceae evice quality een he autho would like to expe thei thank to the Euopean Coiion fo thei uppot in the MicoGid- poject ENK5-C F. D. Kanello i with the School of Electical and Copute Engineeing, National echnical Univeity of Athen, Geece (e-ail: kanello@ail.ntua.g). A. I. ouchnika i with the School of Electical and Copute Engineeing, National echnical Univeity of Athen, Geece (e-ail: aggelo@powe.ece.ntua.g). N. D. Hatziagyiou i with the School of Electical and Copute Engineeing, National echnical Univeity of Athen, Geece (e-ail: nh@powe.ece.ntua.g). Peented at the Intenational Confeence on Powe Syte anient (IPS 5) in Monteal, Canada on June 9-2, 25 Pape No. IPS5 - by end cutoe. Micogid can povide netwok uppot in tie of te by elieving congetion and aiding etoation afte fault. he developent of icogid can contibute to the eduction of eiion and the itigation of cliate change. hi i becaue available and cuently developing technologie fo ditibuted geneation unit ae baed on enewable ouce and ico ouce that ae chaacteized by vey low eiion. echnical challenge aociated with the opeation and contol of icogid ae iene. Enuing table opeation duing netwok ditubance, aintaining tability and powe quality in the ilanding ode of opeation equie the developent of ophiticated contol tategie fo icogid invete in ode to povide table fequency and voltage in the peence of abitaily vaying load. hi pape objective ae to deontate the tanient of a icogid due to intentional ilanding poce and to illutate the aintenance of tability of the icogid in the iolated ode of opeation fo vaying load and cliate condition. he contol appoach ued in thi pape i the ipleentation of conventional f/p, V/Q doop into the gidide invete, thu downcaling the conventional gid contol concept to the BES invete. In thi way, expenive contol bu yte equiing counication and exta cabling ae avoided. Futheoe, fo the adjutent of the fequency, the output active powe of the invete i eaued and the output fequency i etiated accoding to the fequency doop. hi appoach peent eveal advantage a low cot, iple expanion of the yte, inceaed edundancy and iplified upevioy contol []. II. MICROGRID SYSEM COMPONENS AND MODELING A ingle line diaga of the icogid yte tudied in thi pape i illutated in Fig.. he icoouce conideed copie a photovoltaic geneato equipped with a Maxiu Powe Point acke (MPP) and a fixed peed wind tubine equipped with an induction geneato. A battey i ued a enegy toage unit and i iply epeented a a DC voltage ouce with adequate capacity, capable of eeting the eal and eactive powe coand within pe-pecified liit.

2 daping atix, [ ] i the zeo x atix and [ I ] i the identical x atix. C atix epeent the low and highpeed haft elaticitie while D epeent the intenal fiction and the toque loe. Subcipt {}, {gb} and {g} denote tubine oto, gea-box and geneato, epectively. Fig. 2. hee ae dive tain echanical equivalent Fig.. Single-line diaga of the exained icogid A. Fixed Speed Wind ubine Equipped with Induction Geneato Fo the odeling of the wind tubine oto aeodynaic, the well known aeodynaic powe coefficient ethod C p (λ) i ued: Pa = ω w = ρ A C p ( λ, β ) V () w 2 whee P a i the aeodynaic powe, C p (λ) i the dienionle aeodynaic powe pefoance coefficient, λ i the tip peed atio, ρ=.25 kg/ i the ai denity, A=πR 2 i the oto wept aea, V w i the wind peed, ω i the blade otating peed and w the aeodynaic toque. he equivalent of thee elatically connected ae i ued fo iulating the echanical yte of the wind tubine (Fig. 2). he tate pace equation of the echanical yte ae the following [2]: d [] [] I [] θ θ ω [ H] [ C] [ H] [ D] ω + = [ H] (2) dt whee θ = θ, θ, θ ] i the angula poition vecto, [ gb g ω = [ ω,ωgb,ωg ] i the angula peed vecto and = [ w,, g ] i the extenal toque vecto copiing the aeodynaic and the electoagnetic toque, w and g acting on the tubine and geneato oto, epectively. H H = H gb i the inetia atix, H g C C [ ] i the tiffne atix, C = C C + C C C C DR + d d [ D] = d DGB + d + d d i the d + DG d Fo the induction geneato, the well known 4 th ode dq odel i ued, expeed in the abitay efeence fae, otating with an angula velocity ω []: u = ω Ψ + pψ u d d u q d q d q = i + ω Ψ + pψ () = = (ω ω ) Ψ d q q d + pψ u q = = iq + (ω ω ) Ψ d+ pψ q whee d p =, and ω ο i the bae electical angula ω o dt fequency. Geneato convention i ued fo the tato cuent. he zeo equence equation i oitted, ince the achine tato i connected. he tato and oto fluxe ae elated to the cuent by: Ψ = X + X Ψ Ψ d q d = X = X d q d + X + X Ψ q= X q + X q he electoagnetic toque i given by: e = Ψq id Ψd i (5) q he wind tubine ipleented in thi pape i tall contolled and diectly connected to the low voltage gid with no powe electonic inteface [2,4]. B. Photovoltaic Aay with MPP acke he building block of a PV aay i the ola cell, which i baically a p-n eiconducto junction that diectly convet light enegy into electicity. A ola cell i uually epeented by an electical equivalent one-diode odel [5]-[8], a hown in Fig. : Fig.. Equivalent odel fo a ingle ola cell d q d d (4)

3 he cuent ouce I ph epeent the cell photocuent and R i the eie eitance of the cell. PV cell ae gouped in lage unit called PV odule, which ae futhe inteconnected in a paallel-eie configuation to fo PV aay o PV geneato. Fo an aay with N eie connected cell and N p paallel-connected cell, the aay cuent ay be elated to the aay voltage a [5]: q( V + IR ) I = N p[ I ph I [exp( ]] (6) AKN whee EG I = I ( ) exp[ ( )] (7) AK and q i the chage of an electon, K i Boltzann contant, A i the diode ideality facto, i the cell tepeatue (K), I i the cell evee atuation cuent at, i the cell efeence tepeatue, I i the evee atuation cuent at and E G i the band gap enegy of the eiconducto ued in the cell. he photocuent I ph depend on the cell tepeatue and adiation a follow: S I ph = [ ISCR + ki( )] (8) Whee, I SCR i the cell hot cicuit cuent at efeence tepeatue and adiation, k i i the hot cicuit cuent tepeatue coefficient and S i the ola adiation in W/c 2. he powe-voltage chaacteitic of the iulated PV aay i hown in Fig. 4 (at efeence tepeatue = 28.8 o C ). dp dv = V di dv + I = di dv = I V (9) Meauing the inceental and intantaneou aay conductance, the PV aay voltage can be adjuted to the MPOP voltage [9,]. C. PV Aay Invete Contol Syte he contol yte of the invete of the PV aay [,2] conit of two ajo contol loop: the eactive powe and the DC voltage contol (contol of active powe), a illutated in Fig. 5a and 5b epectively. Fig. 5a. Reactive Powe Contol fo the PV Aay Invete Fig. 5b. DC Voltage Contol fo the PV Aay Invete he eactive powe contol i a feedback loop which continually onito the eo between the eaued eactive powe Q and it et point value Q ef. he afoeentioned eo i ued to adjut the invete teinal voltage o that the deied level of eactive powe i aintained. he DC voltage contol loop conit of a conventional Phae Locked Loop (PLL), fed by a phae efeence δ ef which i poduced by the onitoed diffeence between the efeence DC voltage V DC, ef and the actual DC voltage V DC. Hence, the invete phae angle i adjuted in ode to inject to the low voltage gid, the powe poduced by the PV aay. Fig. 4. Powe-Voltage Siulated Chaacteitic of the PV Aay he axiu powe point tacking technique ued wa the inceental conductance ethod. he baic idea i that at the Maxiu Powe Opeating Point (MPOP) the deivative of the powe with epect to the voltage vanihe becaue the MPOP i the axiu of the powe cuve, a hown in Fig. 4. Note that to the left of the MPOP the powe i inceaing with the voltage, i.e. dp/dv > and it i deceaing to the ight of the MPOP, i.e. dp/dv <. Hence, at the MPOP: D. Battey Invete Contol Stategy A an enegy toage device, the battey hould alway povide the deanded powe in ode to keep the icogid fequency and voltage contant at thei pedeteined value (e.g. 5 Hz, p.u.). he appoach ued in thi pape, i the ipleentation of conventional f/u doop into the batteie invete, thu downcaling the conventional gid contol concept to the low voltage gid [, ]. By thi way expenive

4 contol bu yte ae eplaced by uing the gid quantitie voltage and fequency fo the coodination of the coponent. Fo the adjutent of the fequency the output active powe i eaued and the output fequency i calculated accoding to the fequency doop. he battey invete powe output i egulated accoding to the pedeteined doop chaacteitic. Doop contol conit of a fequency doop contolle and a voltage doop contolle, a hown in Fig. 6a and 6b epectively. Fig. 6a. ypical fequency doop chaacteitic Fig. 6b. ypical voltage doop chaacteitic Siilaly to fequency contol, the voltage contol objective i to aintain output voltage cloe to noinal value. E. Modeling of Load Electical load ae aued both a contant active and eactive powe load and contant R-L load. he fit auption i odeled by the following dq-axi cuent coponent obtained fo the abobed active and eactive powe: VP VQ q VP d q VQ d Id = +, I q = () Vd + Vq Vd + Vq Vd + Vq Vd + Vq Auing that fo the contant R-L load the load eitance R i connected in eie with the load inductance L, then the voltage dop aco the load V L ay be elated to the load cuent I L a: dil VL = RIL + L () dt toage unit and i iply epeented a a DC voltage ouce with adequate capacity, capable of eeting the eal and eactive powe coand within pe-pecified liit. Wind peed and ola adiation vay andoly duing iulation o that a lage et of opeating point i exained. Fo the illutated eult, bae powe of kw and bae voltage of 8V, ae ued. wo contant adittance load with Y =.25- j.25 p.u. and Y 2 =.5-j.725 p.u. have been conideed. he paaete of fequency and voltage doop chaacteitic ae f o =5Hz, R f =-.2,V o =p.u., R v =.5. Duing the fit 7 econd of the iulation icogid i diconnected fo the electical gid. he next 7 econd icogid i connected to the electical gid while duing the lat 7 econd it i again diconnected. Wind peed and ola adiation tie-eie ae hown in figue 7 and 8, epectively. he poduced powe by the wind tubine, the photovoltaic and the BES ae hown in Fig 9, and, epectively, whee geneato convention ha been aued. Duing the ilanded ode of opeation BES contol yte continuouly adjut output active and eactive powe in ode to keep the enegy balance and alo fequency and voltage cloe to thei noinal value. Howeve, when icogid i connected to the gid output active and eactive powe ae fixed to contant efeence value, p.u. and.5 p.u., epectively. Voltage pofile at wind tubine and photovoltaic coupling node i hown in figue 2. BES contol yte keep the voltage cloe to p.u., duing ilanding. Siilaly, contol yte aintain fequency cloe to 5 Hz duing ilanded ode of opeation. When icogid i connected to the electical gid, fequency i fixed at 5 Hz. he obeved voltage and fequency deviation can be even alle by changing the paaete of the voltage and fequency doop chaacteitic (Fig 6). In Fig. 4 the aplitude of the cuent flowing fo to the gid i hown. he tanient ocillation of the voltage at wind tubine, photovoltaic coupling node and of the cuent flowing to the gid ae hown in figue 5 and 6. anient ocillation of 5 Hz occu duing connection poce and ae being daped in about.5 ec. Contol yte epone duing the tanient phenoenon i table and fat, enuing table tanition to diffeent ode of opeation of the icogid. 5 4 III. SIMULAION RESULS he ingle line diaga of the icogid yte tudied in thi pape i illutated in Fig.. he icoouce conideed copie a photovoltaic geneato equipped with a Maxiu Powe Point acke (MPP) and a fixed peed wind tubine equipped with an induction geneato. Diffeent netwok configuation (e.g. ing configuation) have alo been exained and it wa hown that the popoed contol tategie pefo the ae. A battey i ued a enegy wind peed (/ec) Fig. 7. Wind peed (/ec)

5 ola adiation (%) voltage aplitude,pv and W node (p.u.) W PV 6 Fig. 8. Sola adiation (%).9 Fig. 2. Voltage aplitude at wind tubine, photovoltaic bue (p.u.) wind tubine active, eactive powe (p.u.) P Q fequency (Hz) Fig. 9. Wind tubine active, eactive powe (p.u.) 49.6 Fig.. Fequency eaued at W node (Hz.).45 P Q photovoltaic active, eactive powe (p.u.) Fig.. Photovoltaic active, eactive powe (p.u.) gid cuent (p.u.) Fig. 4. Aplitude of cuent flowing to the gid (p.u.) active, eactive powe of BES (p.u.) Fig.. Battey active, eactive powe (p.u.) P Q voltage aplitude duin gid connection,pv and W node (p.u.) W PV Fig. 5. anient voltage of W and photovoltaic coupling node duing connection to the gid (p.u.)

6 cuent duing gid connection (p.u.) PHOOVOLAIC N =22, N p=8 I = 9.969* -6 A, =.8 o K, K i =.7 A/ o C, I c = 2.52 A, =.2eV, A =.92, K/q = 8.62* -5 ev/ K, R =.2 Ω MPP Voltage Contolle K v =., I v =.5 Bae Quantitie f b =5 Hz, V b =8 V, S b = kw E g Fig. 6. Cuent tanient duing connection to gid (p.u.) IV. CONCLUSIONS In thi pape, the opeation of a typical icogid i tudied. he odel of two dipeed geneation unit (wind tubine, photovoltaic yte) ae peented. Alo odel and tategie fo fat contol of icogid fequency and voltage without counication ae deived. he appoach ued in thi pape, i the ipleentation of conventional f/u doop into the batteie invete, thu downcaling the conventional gid contol concept to the low voltage gid. he afoeentioned odel ae cobined togethe and the odel of a typical icogid i iulated. he tanient due to intentional ilanding poce ae illutated and it i poved that the popoed contol chee aintain fequency and voltage cloe to thei noinal value fo vaying load and cliate condition duing ilanded ode of opeation. Futheoe, the tability of the icogid i enued duing connection and diconnection to the gid. V. ACKNOWLEDGMEN he autho gatefully acknowledge all patne of the MICROGRIDS poject (Contact ENK5-C-22-6), epecially of WPA, fo thei invaluable collaboation. VI. APPENDIX he paaete of the yte depicted in Fig. ae given next. INVERER CONROL SYSEM/DROOP PARAMEERS Fequency Contolle f o = p.u.,r f =-.2 Voltage Contolle V o =p.u, R v =.5 WIND URBINE R=7.6, C p,ax =.4, P no =9kW Induction Geneato Stato eitance,.2 (p.u.) Roto eitance,.2 (p.u.) Stato leakage Reactance, X l.62 (p.u.) Roto leakage Reactance, X l.262 (p.u.) Magnetizing eactance, X.2 (p.u.) VII. REFERENCES [] Engle A., Applicability of Doop in Low Voltage Gid, Intenational Jounal of Ditibuted Enegy Souce, Vol., nube, pp -5, Septebe 24. [2] F. D. Kanello, N. D. Hatziagyiou, "he effect of vaiable peed wind tubine on the opeation of weak ditibution netwok," IEEE an. Enegy Conveion, vol. 7, pp , Dec. 22. [] Chee-Mun Ong, Dynaic Siulation of Electic Machiney Uing Matlab /Siulink, Pentice Hall PR, New Jeey, 998. [4] S. A. Papathanaiou, M. P. Papadopoulo, "Dynaic behavio of vaiable peed wind tubine unde tochatic wind, " IEEE an. Enegy Conveion, vol. 4, pp , Dec [5] R. A. Meenge, J. Vente, Photovoltaic Syte Engineeing (2nd ed.), CRC Pe, New Yok, 24. [6] O. Waynczuk, N. A. Anwah, "Modeling and dynaic pefoance of a elf-coutated photovoltaic invete yte, " IEEE an. Enegy Conveion, vol. 4, pp , Sep [7] G. Vachtevano, K. Kalaitzaki, "A hybid photovoltaic iulato fo utility inteactive tudie, " IEEE an. Enegy Conveion, vol. EC-2, pp , June 987. [8] A.D. Hanen, P. Søenen, L. H. Hanen and H. Bindne, "Model fo a Stand-Alone PV Syte, " Riø National Laboatoy, Rokidle, ech. Rep. Riø-R-29 (EN)/SEC-R-2, Dec. 2. [9] K. H. Huein, I. Muta,. Hohino, M. Oakada, "Maxiu photovoltaic powe tacking: an algoith fo apidly changing atopheic condition, " IEE Poc.-Gene. an. Ditib., vol. 42, pp.59-64, Jan [] C. Papanavaat, M. Bane and N. Jenkin, "Invetigation of the pefoance of a photovoltaic ac odule, " IEE Poc.-Gene. an. Ditib., vol. 49, pp , July 22. [] M. R. Patel, Wind and Sola Powe Syte, CRC Pe, New Yok, 999. [2] Siegfied Heie, Gid Integation of Wind Enegy Conveion Syte, John Wiley & Son Ltd, Wet Suex, 998. [] M. C. Chandoka, D. M. Divan and R. Adapa, "Contol of paallel connected invete in tandalone ac upply yte, " IEEE an. Induty Application, vol. 29, pp. 6-4, Jan.-Feb. 99. VIII. BIOGRAPHIES F. D. Kanello gaduated fo the Depatent of Electical and Copute Engineeing of NUA in 998. He eceived the Docto of Engineeing degee in 2. Hi eeach inteet include odeling and contol of wind tubine, odeling-yte identification of netwok with ebedded wind pak, powe electonic and neual netwok. A. I. ouchnika eceived hi Electical and Copute Engineeing degee at National echnical Univeity of Athen (NUA), in 24. He i PhD tudent in the Electical Engineeing Depatent of NUA. Hi eeach inteet include enewable enegy ouce and dipeed geneation. N. D. Hatziagyiou i Pofeo at Powe Diviion of the Electical and Copute Engineeing Depatent of NUA. Hi eeach inteet include enewable enegy ouce, dipeed geneation, dynaic ecuity and AI technique. He i ebe of CIGRE SCC6 and enio ebe of IEEE.