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A MAXIMUM POWER POINT TRACKING APPROACH FOR ADAPTING CHANGING ENVIRONMENTAL CONDITIONS Trirtfng ViftAnh Nguyin Thanh Thu^n Trifdng Dgi hgc Suphgm Ky IhudI Tp.HCM Trudng CDN Cdng ngh? cao Ddng An
Nhgn ngdy 15 thdng 3 ndm 2011, chdp nhgn dang ngdy 7 thdng 6 ndm 2012 T 6 M TAT
Bdi bdo trinh bdy phuxmg phdp tim diim Idm vl$c cd cdng suit eye 691 cda pin m$t tr&i (MPPT) ddp (mg cdc diiu kl$n mdi tnjf(mg thay dii. Phuong phdp mCrl di xuit phdn chia vdng Idm viic trin dutmg d$c tuyin cua pin m$t triri thdnh ba vdng chinh, g6m vdng bdn trdi diim cgc d^l (MPP), vdng ciK d?/ vd vdng bdn phdi diim MPP B^ng vi$c xdc djnh diim Idm vide cOa pin m$t trdi dang & vOng ndo diu cd thi nhanh chdng dira pin vdo Idm vi$c & diim eye d^i thdng qua vi$c diiu chinh dd rdng xung cOa m^ch boost.
Kit qud md phdng vd thgc nghi$m cho thiy phuong phdp ndy d§ tim dux?c diim MPP nhanh hem, 6n djnh hon vd khdc phgc dux?v mdt s6 nhuoc diim cua gidi thudt P&O (Perturb and Observe).
ABSTRACT
This paper presents the Maximum PowerPoint Tracking (MPPT) technique of Photovoltaic to adapt changing enviromental conditions. The author uses the new method by dividing the working point on the characteristics of solar cells into three major areas, including the left side of the maximum power point (MPP), the maximum area and the right of the MPP area. By defining the working point of the solar cells we can quickly take the Photovoltaic to work at the MPP by adjusting duty pulse of the boost circuit.
Results of simulations and experimental measurements have shown that this method has found the MPP faster, more stable and overcomes some disadvantages of the algorithm P&O.
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Phat dien bdng pin quang dien (PV) ngay edng trd nen quan trgng bdi vi nd dugc xem la ngudn nang lugng tdi tao cd nhieu uu diem nhu khong phat sinh chi phi nhien lieu, khdng gay 6 nhiim mdi trudng, ddi hdi bdo tri it va khong phat ra tidng 6n so vdi cac nguon ndng lugng khac. Tuy nhien, cac module PV khi Idm viec vdi tdng trd tai khdng thich hgp vdned hifu suat chuydn ddi thdp, do dd,d6 tim diem cdng suat eye dai (MPPT) cho PV la didu cdn thidttrong mgt he thdng PV.
Lugng difn nang tao ra phy thugc vao dien dp ho^t dpng ciia PV. Tren dac tuydn V(I) va P(V) ciia PV tdn tai duy nhdt mpt didm md d dd cong suat phat ciia PV dat cue dai (MPP), didm MPP nay thay ddi phu thugc vao buc xa va nhiet dp moi trudng. Nhiem vu ciia bp MPPT id tim va duy U-i chd dp Idm viec hieu qua nhdt. Vi vay,nhieu phuang phap MPPT da dugc nghien eiiu de xac dinh didm lam viec tdi uu.
Trong [l],vdi ky thugt MPPT diing bang tra tren may tinh nen ggp nhieu khd khan ve bg nhd trong bd vi xii ly.Giai quyet vdn de nay, mpt sd nghien cijm sir dung phuong phap thyc nghiem de chi ra quan he gi&a dien ap lam viec tdi uu va dien dp hd mach ciia PV [2],[3] nhung ehi dp dung dupe mdt so lo^i PV nhat dinh vi quan hf nay phu thupc vao vat lieu ehe tao, nhift dp moi trudng. Cac giai thuat mdi [4],[5]
su dung ky thuat P&O (perturb and observe)hay cai tien cua P&O da khdc phyc duge nhugc diem ndi tren. Tuy nhien, cdng suat PV thu dugc bi dao dpng Idn va de tim sai diem MPP khi bde xa thay ddi. Ngoai ra, hien nay cae phuang phap MPPT su dyng logic md hay m^ng Noron cung duge ehii trgng phdt trien nhung dp phiie tap cao [6]-[9].
Bai bao tap trung nghien cuu xay dung gidi thuat MPPT cd tdc dp tim diem cue dai nhanh chdng va cd kha nang dap img dudi cac dieu kien moi trudng thay ddi dya tren nhung uu diem ciia phuang phap P&O va phuong
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Hinh I. Sadd khdi h4 thdng PVcd MPPT Cdng sudt eiia PV dugc xdc djnh bang tich s6 cua hai gid trj Ipv vd Vpv B$ MPPT xdc djnh gid trj di^n dp V„r (hogc d0 r^ng xung) nhdm didu khien b$ bidn ddi ndng lugng DC- DC sao cho difn dp DC dgt Ifin tdi thay ddi dd thay ddi dugc cdng sudt tieu thy phii hgp vdi cdng sudt cue dgi ciia PV.
2.2Phdn tich gidi thuSt P&O truydn thdng
Hinh 2. Dg doc dP/dV cua P V X6t hinh 2, gidi thugt P&Ovdn dya vdo quan hf V-P cua PV, bSn trdi didm eye dgi (MPP) dP/dV > 0, trong khi d ben phai didm MPP. dP/dV < 0. Ndu difn dp vgn hdnh ciia PV dugc di theo hudng dP/dV > 0, didu ndy cho thay PV dang di den diem MPP. ngugc Igi ndu di theo hudng dP/dV < 0, diem 1dm vifc dd di qua didm MPP, khi dd giai Ihugl P&O se dao chieu (hinh 3). Vi vay giai thuat nay cd nhieu mat han che nhu luon ludn giao dgng quanh diem MPP, dap img cham, va cd the ddp img sai dudi cac dieu kifn mdi trudng thay ddi (HiNH4). Khi_ birc xa thay ddi PV chuydn dudng dgc tuyen thap len dgc tuyen cao. Khi dd AP = (Pk,, - Pk) > 0 vd AV > 0. gidi thuat tidp tyc tang V,ef lam cho diem idm viec ngdy cdng
xa didm MPP.
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Hinh 4 Gidi thugi P&O tim sai diem MPP 2.3 Giai thu^tddxuSt
I. Vimg Idm vii>c hi^u qud cua PV Neu chia dgc tuyen ciia pin mat trdi thdnh ba viing nhu hinh 5, vdng ben trdi diem MPP (viing I), vung MPP (viing 2) vd vung ben phdi diem MPP (vimg 3) Cdc gid tri VLOW va VHIGH dugc xdc djnh dya tren phuang phdp thuc nghifm. Theo [2],[3] VMPP^ ^ (0.75-0_.85)Voc.
Nhung dd do dugc VQC. can phdi ngat PV ra khdi hf thdng, nen chi phi mach dpng luc tang, that thodt cdng suat cung nhu dao dgng cdng suSt,cung cd the diing pin mdu dd xac djnh dien dp Voc- nhung khong chinh xac va Idm gid thanh he thdng tdng cao. Vi vay, dd dam bao dd diem MPP ludn ndm trong viing 2,cd thd chgn:
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Trong dd: Vocrefld difn dp hd mgch tgi nhift dO chudn cua PV do nhd sdn xudt cung cdp.
2. Xdy dimg gidi thugt dieu khiin Sau khi xdc djnh dugc difn dp 1dm vifc Vpvciia hf thdn^, cdn so sdnh vdi hai gid trj VLOW vd VHIGH de xdc djnh gid trj Vref theo cdc quy lugt sau:
Viing I: Vpv< VLOW, tdng nhanh VRLF vdi gia s6 Idn dd nhanh chdng dua PV vdo vimg 2
- Vdng 2: VLOW< Vpv<yHiGH, thyc hifn dd didm MPP vdi gia s6 nhd, dd trdnh df dao d<lng cdng sudt Idn
- Viing 3: VPV>VHIOH, giam nhanh VREF vdi gia sd Idn dd nhanh chdng dua PV trd Igi vdng 2
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Hinh 5. Ba vung Idm viec cua PV Giai thugt mdi dd diem MPPT dugc trinh bdy tai hinh 6, vi sy phdn chia vimg dd nen tin hieu dd bdng cdch so sanhP(k) vd P(k-l) chi diln ra khi Vpv trong viing 2, ngodi yiing ndy, tin hifu dd bf MPPT se su dung sai sd gi&a Vpv vdi VLOW hogc VHLGH- Nhd dd han chddugc viec tim sai didm MPP khi birc xa thay ddi mpt khodng Idn (cdc hien tugng bdng do, bdng che do mdy).
Ndu didm lam viec ciia PV dang d viing 1, xa didm MPP thi dii khi do P(k)_< P(k-l) do biic xa mgt trdi giam, gidi thuat vdn tdng V„f- (hinhd).
Khi PV dang lam vifc d viing 2, neu ed su thay ddi trong sd gia cdng sudt, giai thudt se didu chinh gid trj VREF(dg rgngxung) vdi gia sd nhd, didu ndy giiip cho he thdng^ lam viec dn dinh, hay dd giao ddng cdng sudt vd dien dp nhd. Chang han ndu nhu AP > 0 vd AV > 0
chiing td rdng cdng sudt pin mgt trdi cd the cung cdp hon nOa, gidi thugt sS tdng gid trj Vrefbdng cdch gidm dO rf ng xung dd ddy cdng sudt PV ddn didm Idm vifc mdi cd cdng sudt cao hon didm Idm vifc cQ.
Hinh 6. Gidi thudt de xudt Hinh 7 md ta gidi thugt dd xudt ti trudng Mattab & Simulink.
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Khi bi>c xg thay d6i khdng lifn tyc:
Hinh 8. cho thdy difn dp pin mgt trdi khi sir dyng gidi thugt dd xudt nhanh chdng 1dm vifc tgi difn dp cd cdng sudt eye dgi (khodng 40s) trong khi gidi thugt P&O cd tdc dO dd tim chgm hon (khodng 170s). Cdng sudt tuong dng thu dugc cua gidi thugt dk xudt Idn hdn gidi thugt P&O (hinh 9)
Khi birc xg thay ddi lien tyc: hInh 10 cho thdy difn dp PV ludn hogt d^ng trong viing eye dgi vd cdng sudt PV thu dugc tdn hon gidi thugt P&O khi bde xg thay ddi nhanh (hinh 11).
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Hinh W Diin dp PV khi birc xg thay ddi nhanh
Hinh 12 Dien dp MPP so vdi gidi thudt P&O
Thdng thudng ddi vdi cdc b$ MPPT.
ngir^l ta vSn thudng cdi dgt trudc gid trj V^f hogc d^ r<yng xung chudn, gid trj ndy thudng Id gid trj eye dgi tifu chudn cua PV, vifc cdi dgt ndy nhdm nhanh chdng dim PV vdo hogt d$ng is MPP. Tuy nhifn khi cdi dgt gid trj ban ddu ndy b^ MPPT sir dyng gidi thugt P&O cd thd phdt hifn sai didm MPP.
Trong hinh 12 gidi thugt P&O i ^ t hifn sai didm MPP vd tidp tyc Idm gidm difn dp V„r trudc khi tang trd Igi d gifly thO: 95. Trong khi giai thugt dd xudt da khdc phyc dugc nhugc didm ndy vd cdng sudt thu dugc tir PV Idn hon gidi thugt P&O (hinh 13).
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Hinh li. Cong sudt PV thu dugc luang ung vdi diin dp vgn hdnh cua P V khi buc xg lhay doi nhanh
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Hinh 13. Cong sudl P\' thu dugc luang ung vdi dien dp Idm viic (Vset = 17V)
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Hinh 14 m6 ta mOt hf thing PV g6m pin quang d i ^ 15W, qua bO MPPT ddng c6ng ngh?
m^ch boost vi ket n6i vdi tai tro c6 c6ng sudt dinh mftc & 20W/220V.D6 thj cdng sudt phit ciia hi th6ng PV Iin lu?t du(ic trinh biy tai Hinh 15 tir 14:00 - 15:00 ngiy 25/2/2012 v4 t?i Hinh 19tCt7:00- 18:00 ngiy 02/3/2012.
Hinh 16 cho thS^ sau khoing 7.5s pin m|t triri boat dOng or difim cd c6ng su§t cue dai cong suit t6i iru thu duvc vio khoang 12W.
COng suit thu dugc nfty c6 gii trj gin gid trj Pp.,k cua PV do nhi san xuit cung cip. Liic niy hifu suit d?t 80%
Hinh 15. Cong sudl PV thu dugc 14h ngdy 25/02/2012
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T-^P CHi KHOA HQC & C O N G NCHt CAC TRirONG Oi^l HQC K* THU*T * S 6 89 - 2012 Hinh 19 cho thdy trong mOt ngdy tifiu
bidu pin mgt trdi ludn hogt df ng tgi nhOng didm cd cdng sudt eye dai, cdng sudt ciia pin ludn giao dfng quanh didm cd cdng sudt Idn nhdt.
hinh 19 cQng cho thdy dugc cdng sudt pin mgt trdi thu dugc phy thu0c vdo lugng biic xg trong ngdy.
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Bdi bdo dd xuit gidi thugt MPPT mdi ddp ihig cdc didu kifn mdi trudng thay ddi. Kdt qud Bdng Ihdng sd cua pin mdi trdi lh\/tc nghiem:
mO phdng vd thyc nghifm cho th4y khi surdyng gidi thugt dd xiidt pin mgt trdi luOn hogt dOng tgi nhQng didm cd cdng sudt eye dgi. Kdt qua so sdnh vdi gidi thugt P&O cho thdy gidi thugt df xudt cd tdc d^ tim didm MPP nhanh hem, d$
giao dfing cdng sudt nhd hem vd gidi thugt dd khdc phyc dugc nhugc didm tim sai didm MPP cCia gidi thugt P&O khi didu kifn biJtc x9 thay ddi nhanh.
M6 hinh ihyc nghiem
TAi L i $ U THAM K H A O
Ibrahim. H. E.-S. A. and Houssiny, F. F., "Microcomputer Controlled Buck Regulator fw Maximum Power Point Tracker for DC Pumping System Operates from Photovoltaic System." Proceedings of the IEEE International Fuzzy Systems Conference. August 22-25.Vol. I. pp. 406-411 (1999).
Jawad Ahmad, and Hee-Jun Kim "A Voltage Based Maximum Power Point Tracker for Low Power and Low Cost Photovoltaic Applications" World Academy of Science, Engineering and Technology 60 2009 Masoum. Mohammad A. S. Dehbonei, Hooman, "Design. Construction and Testing of a Voltage-based Maximum Power Point Tracker (VMPPT) for Small Salcllile Power Supply" SSCy9-XII-7 Enslin, J. H. R.. and Snyman, D. B.. "Simplified Feed-Forward ConUol of the Maximum Power Pont in PV Installations" Proceedings of the IEEE International Conference on Power ElecUonics Motion Control, Vol.1, pp. 548-553 (1992).
Sree Manju B, Ramaprabha R. Mathur B.L "Design and Modeling of Standalone Solar Photovoltaic Charging System"!ntemationa! Journal of Computer Applications (0975 - 8887) Volume 18- No 2. March 2011
Md>ssa Farhat. Lassflad Sbila "Advanced I u/yy MPPT Control Algorithm for Photovoltaic S>stems "
SLicncc Academy Transactions on Renewable I- ncrg^ Systems Engineering and Technology Vol. 1. No. 1, March 2011
Mohamed Salhi. Rachid El-Bachui "Maximum Power Point Tracker using Fuzzy Control for Photovoltaic System" International Journal of Research and Reviews in Electrical and Computer Engineering (URKl.ri:) Vol. 1. No. 2. June 2011, ISSN: 2(14(>-?149
R. Bclaidi. M. Falhi, A. Iladdouchc. A. Chikouche, G. Mohand Kaci and Z, Sm,ira, " Study and Simulation of a Mppl controller based on Fuzzy logic coniroller for photovoltaic system" IGEC-Vl-2011-208 Theodores L. Kutias, Alhanassios D. Karlis. "Ne\\ Maximum Power Point Tracker for PV Arrays Using Fuzzy Controller in Close Cooperation With Fuzzy Cognitive Networks" IEEE TRANSACTIONS ON ENERGY CONVERSION. VOL. 21, NO 3, SEPTEMBER 2006
Dja chi lien hi- Truong Vift A n h - T e l : (+84)913117659- E-mail: tvanhspkt@yahoo com Trudng D^i hgc Su ph^m Ky thugt thdnh phd Hd Chi Minh S6 I, Vd Vdn Ngdn, Qugn Thii Dire. Tp. H6 Chi Minh