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Solar Cell - MPPT

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    Li ni u

    1

    Contents

    Li ni u ................................................................................................................ 3Chng 1 ................................................................................................................... 6TNG QUAN V H THNG PIN MT TRI.................................................... 61. Gii thiu v pin mt tri ...................................................................................... 61.1. nh ngha. ......................................................................................................... 61.2. c tnh lm vic ca pin mt tri. .................................................................... 71.3. ng dng ......................................................................................................... 91.4. Tm nng lng mt tri.................................................................................. 101.5. Cch ghp ni cc tm nng lng mt tri. ................................................... 10a. Phng php ghp ni tip cc tm mdun mt tri........................................... 10

    b. Ghp song song cc mun mt tri. .................................................................. 12c. Hin tng im nng ..................................................................................... 12

    2. H thng pin mt tri. ......................................................................................... 132.1. H quang in lm vic c lp ....................................................................... 14a. Thnh phn lu gi nng lng. ......................................................................... 14

    b. Cc b bin i bn dn trong h PV.................................................................. 142.2. H quang in lm vic vi li. ..................................................................... 16a. Yu cu v giao din. .......................................................................................... 16

    b. Cc b bin i trong h PV ............................................................................... 172.3. Phng php iu khin MPPT. ..................................................................... 19Chng 2 ................................................................................................................. 22

    CC B BIN I BN DN ............................................................................ 22TRONG H THNG PIN MT TRI LM VIC C LP ........................... 221. B bini DC/DC. ............................................................................................ 221.1. Cc loi b bin i DC/DC ............................................................................ 23a. Mch Buck........................................................................................................... 23

    b. Mch Buck Boost: B iu khin phng c quy.............................................. 261.2. iu khin b bin i DC/DC........................................................................ 29a. Mch vng in p phn hi. .............................................................................. 29

    b. Phng php iu khin phn hi cng sut. ..................................................... 30

    b. Phng php mch vng dng in phn hi ..................................................... 312. B bin i DC/AC. ............................................................................................ 31Chng 3 ................................................................................................................. 33PHNG PHP D TM IM LM VIC TI U MPPT............................ 331. Gii thiu chung .................................................................................................. 332. Nguyn l dung hp ti ....................................................................................... 343. Thut ton xc nh im lm vic c cng sut ln nht MPPT ...................... 353.1. Phng php nhiu lon v quan st P&O ...................................................... 373.2. Phng php in dn gia tng INC ................................................................ 393. Phng php iu khin MPPT. ......................................................................... 413.1. Phng php iu khin PI .............................................................................. 413.2. Phng php iu khin o trc tip tn hiu ra. ............................................. 43

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    Li ni u

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    4. Gii hn ca MPPT. ............................................................................................ 45Chng 4 ................................................................................................................. 46B LU GI NNG LNG.............................................................................. 461. Cc loi c quy. ................................................................................................... 461.1. c quy ch - axit ............................................................................................... 46

    1.2. c quy kim ..................................................................................................... 472. Cc c tnh ca c quy. ...................................................................................... 472.1. Dung lng: (k hiu l C) .............................................................................. 472.2. in p ngng thp nht: ............................................................................... 472.3. in p h mch: ............................................................................................. 473. Ch lm vic ca c quy (xt c quy ch - axit) ............................................. 483.1. Np c quy:....................................................................................................... 483.2. c quy phng:................................................................................................ 483.3. Cc ch ca b ngun np c quy ............................................................... 48

    3.4. Np vi dng khng i:.................................................................................. 493.5. Np vi p khng i ....................................................................................... 493.6. Np ni. ............................................................................................................ 504. Lgic chuyn trng thi qu trnh np c quy t ng........................................ 505. Cc s c cn bo v ca c quy ch - axit.......................................................... 516. Cc tiu ch la chn c quy. .............................................................................. 517. Cc thng s c trng ca c quy Power Sonic nh sau: ................................. 527.1. c tnh phng. ............................................................................................... 527.2. Cc phng php np cho c quy. ................................................................... 55Chng 5 ................................................................................................................. 59TNH TON H THNG PIN MT TRI LM VIC C LP.................... 591. Chn pin mt tri ................................................................................................ 595.1. Xy dng m hnh pin mt tri ........................................................................ 595.2. M phng c tnh lm vic ca pin mt tri .................................................. 612. Tnh chn b bin i DC/DC ............................................................................ 642.1. Tnh chn cun khng L .................................................................................. 642.2. Tnh chn t in trong mch .......................................................................... 652.3. Chn kho K v it........................................................................................ 653. La chn thut ton MPPT cho h...................................................................... 65

    4. Chn phng php iu khin MPPT................................................................. 705. Tnh chn c quy ................................................................................................. 725.1. Tnh chn dung lng cquy ........................................................................... 725.2. Mch np cquy ............................................................................................... 736. Tnh chn b bin i DC/AC. ........................................................................... 756.1. Tnh chn van................................................................................................... 756.2. Tnh ton thng s b lc u ra. ..................................................................... 767. Tnh chn cc mch iu khin trong h thng. ................................................. 768. Gii php ngun .................................................................................................. 79

    9. S dng Simulink m phng vai tr ca MPPT trong h PV ........................ 81Kt lun v xut .................................................................................................. 79Ph lc ..................................................................................................................... 81

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    Li ni u

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    Li ni u

    Ngy nay vi tnh hnh dn s v nn cng nghip pht trin khng ngng, nng

    lng cng th hin r vai tr quan trng v tr thnh yu t khng th thiu trong cuc

    sng. Tuy nhin trong khi nhu cu s dng nng lng ang ngy cng gia tng th cc

    ngun nng lng truyn thng c khai thc s dng hng ngy ang dn cn kit v

    tr nn khan him. Mt s ngun nng lng ang c s dng nh ngun nguyn liu

    ho thch (du m, than ) ang cho thy nhng tc ng xu n mi trng, gy

    nhim bu kh quyn nh gy hiu ng nh knh, thng tng ozn, l mt trong nhng

    nguyn nhn lm tri t m dn ln. Cc kh thi ra t vic t cc nguyn liu ny gy ra ma axit, gy hi cho mi trng sng ca con ngi. Cn ngun nng lng thu

    in (vn cng c coi l mt loi nng lng sch) th cng khng p ng c nhu

    cu tiu th in hin nay trong khi tnh trng mc nc trong h cha thng xuyn

    xung di mc nc cht. Trc tnh hnh , vn phi tm c nhng ngun nng

    lng mi p ng nhu cu s dng nng lng ang ln mnh hng ngy, thay th

    nhng ngun nng lng c hi cho mi trng hoc ang cn kit ang tr nn cp

    thit, i hi nhiu s quan tm.

    So vi nhng ngun nng lng mi ang c khai thc s dng nh nng lng

    gi, nng lng ht nhn Nng lng mt tri c coi l mt ngun nng lng r,

    v tn, l mt ngun nng lng sch khng gy hi cho mi trng ang thu ht s

    quan tm ca rt nhiu nh khoa hc, nh nghin cu v s tr thnh ngun nng lng

    tt nht trong tng lai. H thng quang in s dng nng lng mt tri (H pin mt

    tri) c nhiu u im nh khng cn nguyn liu, khng gy nhim mi trng, t

    phi bo dng, khng gy ting n Hin nay nng lng mt tri c khai thc

    v a vo ng dng trong cuc sng cng nh trong cng nghip di nhiu dng vhnh thc khc nhau, thng thng cp nhit vin.

    Mt h pin mt tri s dng nng lng mt tri c bn bao gm 2 loi: H pin

    mt tri lm vic c lp v h pin mt tri lm vic vi li. Ty theo iu kin v nhu

    cu s dng v v tr a l lp t m h no c ng dng. Trong kh nng ca mnh,

    em ch ch trng n nghin cu cc thnh phn trong h thng pin mt tri lm vic c

    lp.

    Mt h pin mt tri lm vic c lp bao gm: h thng hp th nh sng l cc

    tm pin mt tri ni ghp li vi nhau; Cc b bin i in t cng sut DC/ DC v

    DC/AC v H thng iu tit v lu tr nng lng l cc thit b iu tit sc, bnh c

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    Li ni u

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    quy. Mi mt thnh phn trong h pin mt tri mang nhng nhim v c th ring bit

    mang tnh quyt nh n kh nng lm vic hiu qu ca h quang in . B bin i

    DC/DC s dng thut ton iu khin tm im cng sut ti u lm tng hiu qu lm

    vic ca pin quang in; c quy gip d tr in nng duy tr hot ng cho c h

    thng vo ban m hay khi thi tit m u, nhiu my ma, lc cng bc x nh sngyu khng pht ra in nng; b bin i in nghch lu DC/AC chuyn i dng

    in mt chiu t c quy thnh in xoay chiu (110 V, 220 V) cung cp cho cc thit

    b in xoay chiu.

    n trnh by bao qut c 1 h thng pin mt tri lm vic c lp vi y

    cc thnh phn cn thit trong h. Sau n tp trung nghin cu su hn vo ngun

    in pin mt tri gm pin mt tri, b DC/DC, phng php v thut ton iu khin

    MPPT thy r c tnh lm vic ca pin thay i di tc ng ca nhit thi tit

    v so snh nguyn l lm vic, u nhc im, kh nng ng dng ca cc thut toniu khin MPPT nhm h pin mt tri c lm vic ti u nht.

    n gm c 5 chng vi ni dung tng quan nh sau:

    Chng 1: Tng quan v h thng pin mt tri.

    Chng 2: Cc b bin i bn dn trong h thng pin mt tri lm vic c lp

    Chng 3: Phng php d tm im lm vic ti u MPPT

    Chng 4: B lu tr nng lng (c quy)

    Chng 5: Tnh ton h thng pin mt tri lm vic c lp

    Trong qu trnh thc hin n tt nghip, em cng c c nhng kin thc

    c hc v tip thu thm c mt s kin thc v kinh nghim mi v pin mt tri.

    Trn tt c l em c hc v rn luyn c phng php lm vic, nghin cu mt

    cch ch ng hn, linh hot hn v c bit l phng php lm vic theo nhm. Qu

    trnh lm n thc s rt c ch cho em v nhiu mt.

    y l kt qu tng kt qu trnh 5 nm hc tp ca em nhng do kinh nghim

    thc t ca bn thn cn cha nhiu nn kh trnh khi nhiu thiu st, do cn phi c

    s hng dn, gip ca thy gio. Qua y em xin gi li cm n chn thnh n thyTRN TRNG MINHcng cc cn b nghin cu trong trung tm Hitech Bch Khoa

    H Ni tn tnh ch bo, hng dn v gip em trong sut qu trnh lm n tt

    nghip. Em cng xin cm n cc thy c gio trong b mn T ng ho XNCN trng

    i Hc Bch Khoa H ni to iu kin cho em hon thnh tt quyn n tt

    nghip ny.

    H ni, ngy thng nm

    Sinh vin thc hin

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    Li ni u

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    L TH THU LINH

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    Chng1. Tng quan v h thng pin mt tri

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    Chng 1

    TNG QUAN V H THNG PIN MT TRI

    1. Gii thiu v pin mt tri

    1.1. nh ngha.Pin mt tri cn gi l pin quang in l thit b ng dng hiu ng quang in

    trong bn dn (thng gi l hiu ng quang in trongquang dn) to ra dng in

    mt chiu t nh sng mt tri. Loi pin mt tri thng dng nht hin nay l loi s

    dng Silic tinh th. Tinh th Silic tinh khit l cht bn dn in rt km v cc in t b

    giam gi bi lin kt mng, khng cin t t do. Khi b nh sng hay nhit kchthch, cc in t b bt ra khi lin kt, hay l cc in t tch in m nhy t vng ho

    tr ln vng dn v li mt l trng tch in dng trong vng ho tr. Lc ny cht

    bn dn mi dn in.

    C 3 loi pin mt tri lm t tinh th Silic:

    - Mt tinh th hay n tinh th module. n tinh th ny c hiu sut ti 16%. Loiny thng t tin do c ct t cc thi hnh ng, cc tm n th ny c cc

    mt trng gc ni cc mdule.

    - a tinh th lm t cc thi c t Silic nung chy, sau c lm ngui v lmrn. Loi pin ny thng r hn loi n tinh th, nhng li c hiu sut km hn.

    Tuy nhin chng c th to thnh cc tm vung che ph b mt nhiu hn loi

    n tinh th b cho hiu sut thp ca n.

    - Di Silic to t cc ming phim mng t Silic nng chy v c cu trc a tinhth. Loi ny thng c hiu sut thp nht nhng cng l loi r nht trong cc

    loi v khng cn phi ct t thi Silicon.

    V bn cht pin quang in l mt it bn dn bao gm hai tm bn dn loi P vloi N t st cnh nhau, khc ch pin quang in c din tch b mt rng v c lp N

    cc mng nh sng c th truyn qua. Trn b mt ca pin quang in c mt lp

    chng phn x v khi chiu nh sng vo pin quang in, s c mt phn nh sng b hp

    th khi truyn qua lp N v mt phn nh sng s b phn x ngc li cn mt phn nh

    sng s n c lp chuyn tip, ni c cc cp electron v l trng nm trong in

    trng ca b mt gii hn. Vi cc bc sng thch hp s truyn cho electron mt nng

    lng ln thot khi lin kt. Khi thot khi lin kt, di tc dng ca in

    trng, electron s b ko v pha bn dn loi N, cn l trng b ko v pha bn dn loiP. Khi nu ni hai cc vo hai phn bn dn loi N v P s o c mt hiu in th.

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    Chng1. Tng quan v h thng pin mt tri

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    Gi tr ca hiu in th ny ph thuc vo bn cht ca cht lm bn dn v tp cht

    c hp ph.

    1.2. c tnh lm vic ca pin mt tri.c tnh lm vic ca pin mt tri th hin qua hai thng s l in p h mch

    ln nht VOClc dng ra bng 0 v Dng in ngn mch ISCkhi in p ra bng 0. Cng

    sut ca pin c tnh theo cng thc:

    P = I.U (1-1)

    Ti im lm vic U = UOC/ I = 0 v U = 0 / I = ISC, Cng sut lm vic ca pin

    cng c gi tr bng 0.

    Hnh 1.1. ng c tnh lm vic U I ca pin mt tri

    Hnh 1.2. S tng ng ca pin mt tri

    T s tng ng, ta c phng trnh c trng sng von ampe ca pin nh

    sau:

    hs

    skT

    )IRsv.(q

    01scR

    )IRV(1eIII

    (1-2)

    Trong :

    Iscl dng quang in (dng ngn mch khi khng c Rs v Rsh) (A/m2)

    +-I

    DI

    shI

    shR

    sR I

    UOC

    ISC

    MPPT

    IPV

    UPV

    uMPP, iMPP

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    Chng1. Tng quan v h thng pin mt tri

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    I01 l dng bo ha (A/m2)

    q l in tch ca in t (C) = 1,6.10 -19

    k l h s Boltzman = 1,38.10-23(J/k)

    T l nhit (K)

    I, V, Rs, Rshln lt l dng in ra, in p ra, in tr Rs v Rsh ca pin trongmch tng ng hnh 1.2.

    * Nhn xt:

    - Dng ngn mch Isc t l thun vi cng bc x chiu sng. Nn ng ctnh VI ca pin mt tri cng ph thuc vo cng bc x chiu sng. mi

    tng bc x ch thu c duy nht mt im lm vic V = VMPPc cng sut ln

    nht th hin trn hnh v sau. im lm vic c cng sut ln nht c th hin

    l im chm en to trn hnh v. (nh ca ng cong c tnh)

    Hnh 1.3.S ph thuc ca c trng VA ca pin mt tri

    vo cng bc x Mt tri.

    - in p h mch Vocph thuc trc tip vo nhit nn ng c tnh VA capin mt tri cng ph thuc vo nhit ca pin.

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    Chng1. Tng quan v h thng pin mt tri

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    Hnh 1.4.S ph thuc ca ng c tnh ca pin mt tri vo nhit ca pin- ton b h PV c th hot ng c mt cch hiu qu th ng c tnh ca

    ti cng phi ph hp vi im MPP.

    Hnh 1.5.ng c tnh ti v c tnh ca pin mt tri

    Trn hnh v 1.5 ng OA v OB l nhng ng c tnh ti. Nu ti c mc

    trc tip vi dy pin mt tri th ti c ng c tnh l OA. Khi , pin lm vic im

    A1 v pht cng sut P1. Cng sut ln nht do phi nng thu c l P2. c th thu

    c cng sut P2, cn c mt b iu chnh cng sut lin kt gia dy pin mt tri

    v ti.

    1.3. ng dngPin mt tri c ng dng nhiu ni trn th gii. Chng c bit thch hp

    cho cc vng li in khng n c. Pin mt tri c s dng nhiu trong sn xut

    cng nh trong i sng. Mt ng dng n gin ca pin mt tri trong cuc sng hng

    ngy nh ng h, my tnh Ngoi ra pin mt tri cn c ng dng trong cc thit

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    Chng1. Tng quan v h thng pin mt tri

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    b vn chuyn nh t, my tnh cm tay, in thoi di ng, thit b bm nc Ngy

    nay, nhng ngi nh c gn nhng tm nng lng mt tri trn nc tr thnh ph

    bin v c xu hng tng dn trong tng lai.

    1.4. Tm nng lng mt tri.Tm nng lng mt tri c to thnh t nhiu pin mt tri c th gm 36 n

    72 pin mt tri mc ni tip vi nhau. Qua nhng tm pin mt tri, nng lng mt tri

    c chuyn ho thnh in nng. Mi pin mt tri cung cp mt lng nh nng lng,

    nhng nhiu pin c t tri di trn mt din tch ln to nn ngun nng lng ln

    hn cc thit b in s dng. Mi tm pin mt tri c cng sut khc nhau nh:

    30Wp, 40Wp, 45Wp, 50Wp, 75Wp, 100Wp, 125Wp, 150Wp. in p ca cc tm pin

    thng l 12VDC. Cng sut v in p ca h thng tu thuc vo cch ghp ni cc

    tm pin li vi nhau. Nhiu tm nng lng mt tri c th ghp ni tip hoc song songvi nhau to thnh mt dn pin mt tri. t c hiu nng tt nht, nhng tm

    nng lng phi lun c phi nng v hng trc tip n mt tri.

    Hiu sut thu c in nng t pin mt tri cc vng min vo cc gi trong

    ngy l khc nhau, do bc x mt tri trn b mt tri t khng ng u nhau. Hiu

    sut ca pin mt tri ph thuc vo nhiu yu t:

    - Cht liu bn dn lm pin.- V tr t cc tm panel mt tri- Thi tit kh hu, ma trong nm.- Thi gian trong ngy: sng, tra, chiu

    Cc tm nng lng mt tri c lp t ngoi tri nn thit k sn xut

    m bo c cc thay i ca kh hu, thi tit, ma bo, s n mn ca nc bin, s

    oxi ho Tui th ca mi tm pin khong 25 n 30 nm.

    1.5. Cch ghp ni cc tm nng lng mt tri.Nh ta bit cc mun pin mt tri u c cng sut v hiu in th xc nh

    t nh sn xut. to ra cng sut v in th theo yu cu th phi ghp ni nhiu tmmdun li vi nhau. C hai cch ghp c bn:

    - Ghp nitip cc tm moun li s cho in p ra ln hn.- Ghp song song cc tm mun li s cho dng in ra ln.

    Trong thc t phng php ghp hn hp c s dng nhiu hn p ng c

    yu cu v in p v dng in.

    a. Phng php ghp ni tip cc tm mdun mt tri.

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    (a) (b)

    Hnh 1.6.Ghp ni tip hai mun pin mt tri (a)

    v ng c trng VA ca cc mun v ca c h (b)

    Gi s cc mun u ging ht nhau, c ng c tnh V -A ging ht nhau, cc

    thng s dng on mch ISC, th h mch VOCbng nhau. Gi s cng chiu sng

    trn cc tm l ng u nhau. Khi ghp ni tip cc tm mun ny ta s c:

    I = I1 = I2= = Ii (1-3)

    n

    1i

    iVV (1-4)

    n

    1ii

    n

    1ii PIVI.VP (1-5)

    n

    1ioptiopt

    n

    1ioptioptioptopt PP,VV,II (1-6)

    Trong :

    I, P, V, l dng in, cng sut v hiu in th ca c h.

    Ii, Vi, Pi l dng in, cng sut, hiu in th ca mun th i trong hIopi, Vopi, Popi l dng in lm vic ti u, in th lm vic ti u, cng sut

    lm vic ti u ca cc mun th i trong h

    Iop, Vop, Pop l dng in lm vic ti u, in th lm vic ti u, cng sut lm

    vic ti u ca h

    Khi ti c gi tr 0 < R < , Cc mun lm vic nh cc my pht tng ng. ngc tnh vn ampe ca h bng tng hnh hcca hai ng c trng ca mi mun.

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    b. Ghp song song cc mun mt tri. cch ghp ny, ta cng gi s cc mun u ging ht nhau, c ng c tnh

    V-A ging ht nhau, cc thng s dng on mch ISC, th h mch VOCbng nhau. Gi

    s cng chiu sng trn cc tm l ng u nhau.

    (a) (b)

    Hnh1.7.Ghp song song hai mun pin mt tri (a)

    v ng c trng VA ca cc mun v ca c h (b)

    Khi ta c:

    U = U1 = U2= = Ui (1-7)

    n

    1i

    iII (1-8)

    n

    1i

    i

    n

    1i

    i PVII.VP (1-9)

    n

    1ioptiopt

    n

    1ioptioptioptopt PP,II,VV (1-10)

    ng c tnh VA ca h cng c suy ra bng cch cng cc gi tr dng in

    I ng vi cc gi tr in th V khng i. Trong trng hp ny, cc pin cng lm vic

    nh cc my pht in khi ti c gi tr 0 < R < .

    c. Hin tng im nng

    Xy ra khi ta ghp ni cc mun khng ging nhau, tc l khi cc thng s ISC,VOC, POPTca cc mun pin khc nhau. y l hin tng tm pin yu hn (tc l pin

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    Chng1. Tng quan v h thng pin mt tri

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    km cht lng hn so vi cc pin khc trong dn hoc khi n b che nng trong khi cc

    pin khc trong dn vn c chiu sng) s hp th hon ton cng sut in do cc tm

    pin kho hn pht ra v lm cho cng sut in mch ngoi bng 0. Phn nng lng

    in tm pin yu nhn c t tm pin kho hns bin thnh nhit, lm nng tm pin

    ny ln v c th dn ti h hng. Hin tng im nng ny ch xy ra trn cc pin yuhn cc pin khc trong h, dn ti s h hng h hay lm gim ng k hiu sut bin i

    quang in ca h.

    trnh hiu ng im nng ny, khi thit k phi ghp cc tm pin mt tri cng

    loi, c cng cc thng s c trng trong mt dn pin mt tri. V tr t dn phi trnh

    cc bng che do cy ci, nh ca hay cc vt cn khc trong nhng ngy c nng cng

    nh bo v trnh bi bn ph bm ln mt vng no y ca tm pin v c th s dng

    cc it bo v.

    Hnh 1.8.it ni song song vi mun bo v mun v dn pin mt tri.

    Nhn trn hnh v 1.8 ta thy gi s pin Ci l pin yu nht c bo v bng it

    phn cc thunchiu vi dng in trong mch mc song song. Trong trng hp h lm

    vic bnh thng, cc pin mt tri hot ng iu kin nh nhau th dng trong mch

    khng qua it nn khng c tn hao nng lng. Khi c s c xy ra, v mt nguyn

    nhn no m pin Ci b che v b tng nhit , in tr ca Ci tng ln, lc ny mt

    phn hay ton b dng in s r qua Dit trnh gy h hng cho Ci. Thm ch khi Ci

    b hng hon ton th h vn c th tip tc lm vic.

    2. H thng pin mt tri.H pin mt tri (h PV photovoltaic system) nhn chung c chia thnh 2 loi c

    bn:

    - H PV lm vic c lp- H PV lm vic vi li

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    H PV c lp thng c s dng nhng vng xa xi ho lnh, ni m li

    in khng ko n c. S khi ca h ny nh sau:

    Hnh 1.9.S khi h quang in lm vic c lp

    Cn trong h PV lm vic vi li, mng li pin mt tri c mc vi li in

    qua b bin i m khng cn b d tr nng lng. Trong h ny, b bin i DC/AC

    lm vic vi li phi ng b vi li in v tn s v in p.

    2.1. H quang in lm vic c lpH PV lm vic c lp gm c 2 thnh phn chnh l:

    - Thnh phn lu gi nng lng.- Cc b bin i bn dn.

    a. Thnh phn lu gi nng lng.H quang in lm vic c lp cn phi c khu lu gi in nng c th phc

    v cho ti trong nhng thi gian thiu nng, nh sng yu hay vo ban m. C nhiu

    phng php lu tr nng lng trong h PV. Ph bin nht vn l s dng c quy lu

    tr nng lng. c quy cn phi c mt b iu khin np bo v v m bo cho tui

    th ca c quy.

    b. Cc b bin i bn dn trong h PV.Cc b bn dn trong h PV gm c b bin i 1 chiu DC/DC v b bin i

    DC/AC.

    B DC/DC c dng xc nh im lm vic c cng sut ln nht ca pin v

    lm n nh ngun in mt chiu ly t pin mt tri cung cp cho ti v c quy. B

    bin i DC/DC cn c tc dng iu khin ch np v phng bo v v nng cao

    tui th cho c quy. C nhiu loi b bin i DC/DC c s dngnhng ph bin nht

    vn l 3 loi l: B tng p Boost, B gim p Buck v B hn hp tng gim Boost

    Buck. C 3 loi DC/DC trn u s dng nguyn tc ng m kha in t theo mt chu

    k c tnh ton sn t c mc ch s dng. Ty theo mc ch v nhu cu m

    b DC/DC c la chn cho thch hp.

    MPPT

    Pin

    mt tri

    B bin i

    DC/DC

    c quy B bin iDC/AC

    Tixoay chiu

    Ti 1 chiu

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    Kha in t trong mch DC/DC c iu khin ng ct tng chu k. Mch

    iu khin kha in t ny c kt hp vi thut ton xc nh im lm vic ti u

    (MPPTmaximum power point tracking) m bo cho h quang in c lm vic

    hiu qu nht. Mch vng iu khin v thut ton MPPT s c trnh by chi tit

    chng 3.B DC/AC c nhim v chuyn i ngun 1 chiu sang xoay chiu (110 hoc 220

    VAC, tn s 50Hz hoc 60 Hz) phc v cho cc thit b xoay chiu. C nhiu kiu b

    bin i DC/AC, chng c th lm vic c hai ch l t mt chiu sang xoay chiu v

    c ch t xoay chiu sang mt chiu. Nhn chung, b bin i DC/ AC trong h PV

    c lp c th lm vic mc in p mt chiu l 12, 24, 48, 96, 120, 240 VDC tu

    tng h.

    B bin i dng trong h PV c lp c nhng c im sau:

    - in p ra hnh Sin.- in p v tn s nm trong gii hn cho php.- Bm st c s thay i ca in p vo. - iu chnh in p ra.- Hiu qu cao ivi ti nh.- t to ra sng hi trnh lm h hi n cc thit b in khc nh tivi, trnh gy

    tn hao cng sut, lm nng thit b.

    - C th chu qu ti trong mt thi gian ngn trong trng hp dng khi ng lnnh ca my bm

    - C bo v qu p, bo v tn s, bo v ngn mch.- Dung lng c tnh.- Tn hao khng ti thp

    Cc linh kin bn dn c s dng trong b bin i ny l cc MOSFET, IGBT.

    MOSFET c s dng vi trng hp cng sut ln ti 5kVA v in p l 96 VDC.

    Chng c u im l tn hao cng sut t tn s cao. Do c in p ri l 2 VDC. Cn

    IGBT thng ch c s dng trong nhng h c in p trn 96 VDC.H PV c lp thng s dng b bin i ngun in p 1 pha hoc 3 pha.

    B bin i DC/AC c nhiu loi v cch phn bitchng bng dng sng ca

    in p u ra. C 3 dng sng chnh l: dng sng Sin, gi sin, v sng vung, sng bc

    thang

    Dng sng vung, sng bc thang ngy nay khng cn thng dng na, khng cn

    ph hp vi cc thit b hin i trong khi gi thnh bbin tn loi sng gi sin v sng

    sin ngy cng gim.

    B bin tn cho dng sng gi Sin thng phc v cho cc thit b trong nh nhti vi, radio, l vi sng Cc thit b iu khin phc tp khc nh b sc pin, ph tng

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    trong ng c thay i tc ,my in lase v b iu khin nhit vn c lm vic

    khng n nh. B bin i DC/AC dng sng gi Sin l s la chn rt kinh t v c

    bit ph hp vi h quang in.

    B bin i c dng sng ra hnh Sin ging nh dng sng ca in li nn

    tng thch v p ng vi hu ht cc loi ti. B bin i dng sng sin c gi thnhln hn b bin i dng gn sin, nhng cht lng in p ca b bin i loi ny l

    mt u im ln, thm ch b bin i loi ny cn ph hp vi c cc thit b iu khin

    phc tp v c lm vic khng n nh nh b sc pin, ph tng trong ng c thay i

    tc , my in lase v b iu khin nhit

    Phng php iu khin PWM c s dng gip b bin i to c u ra

    c dng Sin.

    Cc loi b bin i DC/AC trong h pin mt tri c lp ty tng trng hp c

    th c s dng na cu v dng cu 1 pha Chng 2 s trnh by chi tit v cc b bin i DC/AC ny.

    2.2. H quang in lm vic vi li.y l h PV c kt ni vi li in. H thng ny cho php t duy tr hot

    ng ca ti bng ngun nng lng d tr v ng thi cng c th bm phn nng

    lng d tha vo li in bn. Khi ngun pin mt tri (hay my pht pin mt tri)

    sinh ra nhiu nng lng th ngun nng lng d tha ny s c chuyn vo trong

    li in, cn trong nhng iu kin thi tit xu, khng c nng hay my ma, my phtpin mt tri khng sinh ra nng lng p ng cho ph ti th h s ly in t

    li. Do h PV ny c th cn hoc khng cn c quy d tr nng lng. B bin

    i trong h ny khng ch gip n nh ngun nng lng to bi ngun pin mt tri m

    cn phi m bo ngun in nng ra khi h quang in phi ng b vi li.

    H quang in mt tri c th tr thnh mt phn ca li in ln. Cu trc c a

    h cn ph thuc vo quy m ca h v c tnh ph ti s dng. Khi h quang in c

    mc vi li, ngun cng sut c hai chiu hng. Li s hp th ngun in mt tri

    v s cung cp cho cc thit b tiu th khi m h PV khng th sinh ra in vo thi gian

    yu nh sng hoc ban m. y l hnh thc ang c khuyn khch pht trin nhiu

    ni trn th gii.

    a. Yu cu v giao din.H pin mt tri c ni vi li in u ra ca b ngt ng b cui u ra

    ca b i in. Dng chy cng sut ph thuc vo c hai hng ca im tip ni vi

    b ngt. Cc yu cu c bn i vi in p ti im ni l nh sau:

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    - Bin v pha ca in p phi cn bng vi bin v pha ca dng cng sut.in p c iu khin bng h s bin i my bin p v/hoc gc m b

    DC/AC trong h iu khin mch vng kn.

    - Phi m bo ng b vi tn s ca li bng cch s dng tn s h lm tn schun cho tn s ng m ca b DC/AC. H PV phi c bo v ngn mch, qu dng, qu p, ni t, chng st v bo

    v tch bit

    H PV ph thuc vo thi gian chiu sng trong ngy, ph thuc vo c im kh

    hu, c bit l thi gian cao im, c tnh ph ti im cao nht.

    b. Cc b bin i trong h PVB bin i gip lin kt nhng tm pin mt tri vi cc phn cn li trong h PV.

    N gip bin i ngun in mt chiu sinh ra t pin mt tri thnh ngun xoay chiu ho vi li. H PV lm vic vi li i hi phc tp trong hot ng, phi c s

    ng b vi li v in p, tn s, gc pha. B bin i DC/AC phi to c in p ra

    dng sin, phi ng b c v in p, tn s ca li, phi xc nh c im lm

    vic c cng sut ln nht ca dy pin mt tri. u vo ca b bin i ny ph thuc

    vo in p vo cho n khi xc nh c im MPP trn ng c tnh I V. B bin

    i phi iu khin c cc gc pha ca li, v u ra ca b DC/AC ny phi c

    iu khin c v in p v tn s. Cc loi b DC/AC thng thng c th c iu

    khin bng phng php PWM iu chnh rng xung vhot ng trong tn s t2kHz n 20 kHz.

    B bin i lm vic vi li c phn loi rng ri thnh b bin i ngun p

    (VSI) v b bin i ngun dng (CSI). Tu thuc vo s iu khin m b bin i

    DC/AC c phn thnh loi b bin i iu khin dng (CCI) hay b bin i iu

    khin p (VCI).

    Nu b bin i ngun p c mt t in mc song song vi u vo, th b bin

    i ngun dng s c mt cun cm mc ni tip vi u vo mt chiu. Trong b bin

    i ngun dng CSI, ngun 1 chiu xut hin nh dng mt chiu ca b bin i. Pin

    mt tri c th c coi nh mt ngun dng. Hu ht cc b bin i trong h PV l

    ngun p, mc d pin mt tri c coi nh mt ngun dng. Cc b bin i ngun

    dng thng c dng cho cc ng c ln. B bin i ngun p c dng ph bin

    v kt hp vi b bin i ngun p PWM to thnh b bin i dng Sin.

    Hnh 1.10 m t b bin i ngun p xoay chiu c mch hnh cu mt pha VSI

    c iu khin p v gc pha. Vic chuyn i nng lng t pin mt tri c kt hp

    vi vic iu khin gc pha gia in p bin i v in p li. in p bin ithng chm pha hn in p li.

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    Hnh 1.10.B bin i ngun dng CSI

    Hnh 1.11.B bin i VSI ngun p

    Trong hnh 1.11, b bin i ngun p hot ng nh mt b bin i iu khin

    dng CSI. Loi ny s dng phng php PWM iu khin dng qua cc phn t tch

    cc, linh ng trong mch cp cho li.

    C nhiu loi b bin i c s dng cho h PV lm vic vi li, bao gm

    nhng loi sau:

    B bin i c o dng. (line commutated inverter) Mch gm nhng tiristo

    c mc vi li t tr khng v cch ly h vi li v in.B bin i c t o. (Selfcommutated inverter) gm cc kho ng ct vi

    phng php iu khin PWM

    B bin i s dng my bin p tn s cao. dng my bin p tn s cao ~20kHz

    Nhn xtNhn chung, c hai loi h quang in: lm vic vi li v lm vic c lp u

    c nhng c im ring. H quang in lm vic vi li c cu trc n gin, c nhng

    u im v li ch v kinh t ng khuyn khch c p dng rng ri nhng h thng

    ny i hi nhiu yu cu phc tp v cn phi l thuc vo trng thi v c im ca

    li in v phi ng b vi li v in p, pha v tn s. H PV lm vic c lp c

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    cu trc phc tp v c gi thnh lp t cao hn so vi h lm vic vi li nhng li

    c bit thch hp vi nhng vng su vng xa, ni m li in khng ko n c

    hoc chi ph a li in v nhng vng ny thm ch cn cao hn c chiph lp t h

    pin mt tri.

    V yu cu ca ti l nghin cu v thit k h thng pin mt tri lm vic clp nn quyn n ny ch i su vo tm hiu h PV lm vic c lp. Cc thnh phn

    trong h thng PV lm vic c lp s ln lt c trnh by chi tit trong nhng

    chng tip sau y.

    2.3. Phng php iu khin MPPT.MPPT (Maximum Power Point Tracker) l phng php d tm im lm vic c

    cng sut ti u ca h thng ngun in pin mt tri qua vic iu khin chu k ng

    m kho int dng trong b DC/DC. Phng php MPPT c s dng rt ph bintrong h thng pin mt tri lm vic c lp v ang dn c p dng trong h quang

    in lm vic vi li.

    MPPT bn cht l thit b in t cng sut ghp ni ngun in PV vi ti

    khuych i ngun cng sut ra khi ngun pin mt tri khi iu kin lm vic thay i,

    v t c th nng cao c hiu sut lm vic ca h. MPPT c ghp ni vi b

    bin i DC/DC v mt b iu khin.

    Hnh 1.12.B iu khin MPPT trong h thng pin mt tri

    B iu khin MPPT c th l b iu khin tng t truyn thng. Tuy nhin,

    vic s dng b iu khin s ang ngy cng thnh hnh v n c nhiu u im hn b

    iu khin tng t. Th nht l, b iu khin s c th lp trnh c v vy kh nng

    thc hin cc thut ton cao cp s d dng hn. N d dng m ho biu thc, v d x =

    y xz, hn l thit k mt mch in tng t thc hin cng mt biu thc . Nh l

    do ny m vic hiu chnh b iu khin s c thc hin d dng hnnhiu so vi b

    iu khin tng t. Mt khc b iu khin s khng b nh hng bi s thay i v

    nhit v thi gian v b ny hot ng ri rc, bn ngoi cc thnh phn tuyn tnh. Vvy, b iu khin s c trng thi n nh lu hn. Khng ch c vy, b iu khin

    MPPT s khng ph thuc vo dung sai ca cc b phn khc v n thc hin thut ton

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    phn mm, ni m cc thng s c th c gi n nh hoc thay i c. B iu

    khin loi ny cho php gim s lng thnh phn v n ch dng mt chp n lm

    nhiu nhim v khc nhau. Nhiu b iu khin s c trang b thm b bin i A/D

    nhiu ln v ngun to xung PWM, v vy n c th iu khin c nhiu thit b ch

    vi mt b iu khin n l.V nhng u im ca b iu khin s m n s chn phng php iu khin

    s cho MPPT. Vic thit k v m phng MPPT s c thc hin chng 3 vi b vi

    x l hoc DSP v cc thut ton thc hin.

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    Chng 2. Cc b bin i bn dn trong h thng pin mt tri l m vic c lp

    22

    Chng 2

    CC B BIN I BN DN

    TRONG H THNG PIN MT TRI LM VIC C LP

    1. B bin i DC/DC.B bin i DC/DC c s dng rng ri trong ngun in 1 chiu vi mc ch

    chuyn i ngun mt chiu khng n nh thnh ngun in mt chiu c th iu khin

    c. Trong h thng pin mt tri, b bin i DC/DC c kt hp cht ch vi MPPT.

    MPPT s dng b bin i DC/DC iu chnh ngun in p vo ly t ngun pin mt

    tri, chuyn i v cung cp in p ln nht ph hp vi ti. Nhn chung b bin iDC/DC thng bao gm cc phn t c bn l mt kho in t, mt cun cm gi

    nng lng, v mt it dn dng.

    Cc b bin i DC/DC thng c chia lm 2 loi c cch ly v loi khng

    cch ly. Loi cch ly s dng my bin p cch ly v in tn s cao kch thc nh

    cch ly ngun in mt chiu u vo vi ngun mt chiu ra v tng hay gim p bng

    cch iu chnh h s bin p. Loi ny thng c s dng cho cc ngun cp mt

    chiu s dng kho in t. Ph bin nht vn l mch dng cu, na cu v flyback.

    Trong nhiu thit b quang in, h thng lm vic vi li thng dng loi c cch lyv in v nhiu l do an ton. Loi DC/DC khng cch ly khng s dng my bin p

    cch ly. Chng lun c dng trong cc b iu khin ng c mt chiu. Cc loi b

    bin i DC/DC thng dng trong h PV gm:

    - B gim p (buck)

    - B tng p (boost)

    - B o du in p (buck boost).

    - B bin i tng gim p Ck

    Vic chn la loi DC/DC no s dng trong h PV cn tu thuc vo yu cu

    ca c quy v ti i vi in p ra ca dy panelmt tri.

    B gim p buck c th nh c im lm vic c cng sut ti u mi khi in

    p vo vt qu in p ra ca b bin i, trng hp ny t thc hin c khi cng

    bc x ca nh sng xung thp.

    B tng p boost c th nh im lm vic ti u ngay c vi cng nh sng

    yu. H thng lm vic vi li dng b Boost tng in p ra cp cho ti trc khi

    a vo b bin i DC/AC.B Buck boost va c th tng, va c th gim p.

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    23

    1.1. Cc loi b bin i DC/DC

    a. Mch Buck.Kha K trong mch l nhng kha in t BJT, MOSFET, hay IGBT. Mch Buck c

    chc nng gim in p u vo xung thnh in p np c quy. Kha transitor c

    ng m vi tn s cao. H s lm vic D ca kha c xc nh theo cng thc sau:

    tcdngonon f.TT

    TD (2-1)

    Hnh 2.1. S nguyn l b gim p Buck

    Trong thi gian m, kha K thng cho dng i qua, in p mt chiu c np

    vo t C2 v cp nng lng cho ti qua cun khng L. Trong thi gian ng, kha K

    ng li khng cho dng qua na, nng lng 1 chiu t u vo bng 0. Tuy nhin ti

    vn c cung cp y in nh nng lng lu trn cun khng v t in do iot

    khp kn mch. Nh vy cun khng v t in c tc dng lu gi nng lng trong thi

    gian ngn duy tr mch khi kha K ng.

    K

    C1 C2

    L

    V1 V2

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    Hnh 2.2.Dng sng in p v dng in ca mch Buck

    Phn tch mch da trn s cn bng nng lng qua chu k ng ct ca kha:

    Nng lng cp cho ti trong ton b chu k = nng lng thut ngun trong thi gian

    kha m, v nng lng cp cho ti trong sut thi gian K kha = nng lng ly t cun

    khng v t in trong thi gian K kha.

    Hay cng c th phn tch da trn phng php sau:

    iu kin xc lp, s cn bng nng lng trn cun khng trong thi gian kha

    ng m c duy tr.

    Do:

    dt

    dI.Lv LL (2-2)

    nn khi K m (ton):

    onoutinL T).VV(L.I (2-3)

    khi K kha (toff):

    offoutL T.VL.I (2-4)

    ton toff

    T

    -Vo

    Vin-Vo

    V1

    IL IL

    IK

    ID

    t

    t

    t

    t

    t

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    Nu cun khng ln, th dng in cm ng bin thin t, gi tr cc i ca

    dng in c tnh nh sau:

    L21

    omaxL III (2-5)

    Trong : Iol dng ti = Vout/Rti= gi tr trung bnh ca dng in cm ng.

    T cc cng thc trn suy ra:Vout = Vin.D (2-6)

    Cng thc (2 6) cho thy in p ra c th iu khin c bng cch iu khin

    h s lm vic D thng qua mt mch vng hi tip ly gi tr dng in np c quy lm

    chun. H s lm vic c iu khin bng cch phng php iu chnh rng xung

    thi gian m ton. Do , b bin i ny cn c bit n nh l b iu ch xung

    PWM.

    Trong 3 loi b bin i DC/DC trn, b Buck c s dng nhiu trong h thng

    pin mt tri nht v nhiu u im ph hp vi cc c im ca h pin mt tri.

    B Buck c cu trc n gin nht, d hiu v d thit k nht, b B uck cn

    thng c dng np c quy nhng n c nhc im l dng in vo khng lin

    tc v kho in t c b tr v tr u vo, v vy cn phi c b lc tt.

    Mch Buck thch hp s dng khi in p pin cao hn in p c quy. Dng cng

    sut c iu khin bng cch iu chnh chu k ng m ca kha in t. B Buck c

    th lm vic lm vic ti im MPP trong hu ht iu kin nhit , cng bc x.

    Nhng b ny s khng lm vic chnh xc khi im MPP xung thp hn ngng in

    p np cquy di iu kin nhit cao v cng bc x xung thp. V vy

    nng cao hiu qu lm vic, c th kt hp b Buck vi thnh phn tng p.

    a. Mch Boost

    Hnh 2.3.S nguyn l mch Boost

    Ging nh b Buck, hot ngca b Boost c thc hin qua cun khng L.

    Chuyn mch K ng m theo chu k. Khi K m cho dng qua (t on) cun khng tch

    nng lng, khi K ng (toff) cun khng gii phng nng lng qua it ti ti.

    dt

    dI.LVV L01 (2-7)

    KC1 C2

    L

    V1 V0

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    Mch ny tng in p vng khi phng ca c quy ln p ng in p ra. Khi

    kha K m, cun cm c ni vi ngun 1 chiu. Kha K ng, dng in cm ng

    chy vo ti qua it. Vi h s lm vic D ca kha K, in p ra c tnh theo:

    D1

    VV inout

    (2-8)

    Vi phng php ny cng c th iu chnh Tontrong ch dn lin tc iu

    chnh in p vo V1 im cng sut cc i theo th ca ti Vo.

    Hnh 2.4.Dng sng dng in ca mch Boost

    b. Mch Buck Boost: B iu khin phng c quy

    Hnh 2.5.S nguyn l mch Buck Boost

    T cng thc (2-8): Do D < 1 nn in p ra lun ln hn in p vo. V vy

    mch Boost ch c th tng p trong khi mch Buck trnh by trn th ch c th

    gim in p vo. Kt hp c hai mch ny vi nhau to thnh mch Buck Boost va

    c th tng v gim in p vo.

    LC

    V0K

    V1

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    Khi kha ng, in p vo t ln in cm, lm dng in trong in cm tng

    dn theo thi gian. Khi kha ngt, in cm c khuynh hng duy tr dng in qua n s

    to in p cm ng iot phn cc thun. Ty vo t l gia thi gian ng kha

    v m kha m gi tr in p ra c th nh hn, bng hay ln hn gi tr in p vo.

    Trong mi trng hp th du ca in p ra l ngc vi du ca in p vo, do dng ini qua in cm s gim dn theo thi gian.

    Ta c cng thc:

    D1

    DVV inout

    (2-9)

    Cng thc (2-9) cho thy in p ra c th ln hn hay nh hn in p vo ty

    thuc vo h s lm vic D.

    Khi D = 0.5 th Vin = Vout

    Khi D < 0.5 th Vin > Vout

    Khi D > 0.5 th Vin < Vout

    Nh vy nguyn tc iu khin in p ra ca c ba b bin i trn u bng cch

    iu chnh tn s ng m kha K. Vic s dng b bin i no trong h l ty thuc

    vo nhu cu v mc ch s dng.

    b. Mch Ck

    Hnh 2.6.S nguyn l b bin i Ck

    B Ck va c th tng, va c th gim p. Ck dng mt t in lu gi

    nng lng v vy dng in vo s lin tc. Mch Ck t gy tn hao trn kho in t

    hn v cho hiu qu cao. Nhc im ca Ck l in p ra c cc tnh ngc vi in

    p vo nhng b Ck cho c tnh dng ra tt hn do c cun cm t tng ra. Chnh t

    u im chnh ny ca Ck (tc l c c tnh dng vo v dng ra tt.

    Nguyn l hot ng ca Ck l ch dn lin tc. trng thi n nh, in p

    trung bnh ri trn cun cm bng 0, theo nh lut in p Kichp vng mch ngoi

    cng hnh v 2.6 ta c:

    VC1 = VS + Vo (2-10)

    Gi s t C1 c dung lng ln v in p trn t khng gn sng mc d n

    lu gi v chuyn mt lng nng lng ln t uvo n u ra.

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    Chng 2. Cc b bin i bn dn trong h thng pin mt tri l m vic c lp

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    iu kin ban u l khi in p vo c cp v kho SW kho khng cho dng

    chy qua. it D phn cc thun, t C1 c np. Hot ng ca mch c chia thnh 2

    ch .

    Ch 1: Khi kho SW m thng dng, mch nh hnh v 2.7

    Hnh 2.7.S mch b Ck khi kho SW m thng dng.

    in p trn t C1 lm it D phn cc ngc v it kho. T C1 phng sang ti

    qua ng SW, C2, Rti, v L2. Cun cm ln nn gi thit rng dng in trn cun

    cm khng gn sng. V vy ta c mi quan h sau:

    - IC1 = IL2 (2-11)

    Ch 2: Khi SW kho ngn khng cho dng chy qua, mch c dng nh hnh

    v sau:

    Hnh 2.8.S mch Ck khi kho SW ng

    T C1 c np t ngun vo VSqua cun cm L1. Nng lng lu trn cun cm

    L2 c chuyn sang ti qua ng D, C2, v Rti. V vy ta c:

    IC1 = IL2 (2-12)

    hot ng theo chu k, dng in trung bnh ca t l 0. Nn ta c:

    0T)D1.(IDT.I offSW1ConSW1C (2-13)-IL2.DT + IL1.(1D)T = 0 (2-14)

    D1

    D

    I

    I

    2L

    1L

    (2-15)

    Trong : D l t l lm vic ca kho SW (0 < D < 1) v T l chu k ng ct.

    Gi s rng y l b bin i l tng, cng sut trung bnh do ngun cung cp

    phi bng vi cng sut trung bnh ti hp th c.

    Pin = Pout (2-16)VS.IL1 = Vo.IL2 (2-17)

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    Chng 2. Cc b bin i bn dn trong h thng pin mt tri l m vic c lp

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    S

    o

    2L

    1L

    V

    V

    I

    I (2-18)

    Kt hp cng thc (2 - 15) v (218) vo ta c:

    D1

    D

    V

    V

    s

    o

    (2-19)

    T cng thc (2 19):

    - Nu 0 < D < 0,5: u ra nh hn u vo.- Nu D = 0,5: u ra bng u vo.- Nu 0,5 < D < 1: u ra ln hn u vo.

    T cng thc (2 19) ta thy rng c th iu khin in p ra khi b bin i

    DC/DC bng cch iu chnh t l lm vic D ca kho SW.

    Nhn xt:Nh vy nguyn tc iu khin in p ra ca cc b bin i trn u bng cch

    iu chnh tn s ng m kha K. Vic s dng b bin i no trong h l ty thuc

    vo nhu cu v mc ch s dng.

    iu khin tn s ng m ca kha K h t c im lm vic ti u

    nht, ta phi dng n thut ton xc nh im lm vic c cng sut ln nht (MPPT)

    s c trnh by chi tit chng tip sau.

    1.2. iu khin b bin i DC/DCCc cch thng dng iu khin b DC/DC l:

    a. Mch vng in p phn hi.B iu khin Rv l b PI . in p ra u cc ca pin c s dng nh mt

    bin iu khin cho h. N duy tr im lm vic ca c h st vi im lm vic c cng

    sut ln nht bng cch iu chnh in p ca pin ph hp vi in p theo yu cu.

    Phng php ny cng c nhng nhc im sau:

    - B qua hiu sut ca bc x v nhit ca dy pin mt tri.- Khng c p dng rng ri cho h thnglu gi in nng.

    V vy, phng php iu khin ny ch thch hp di iu kin bc x n

    nh, chng hn nh h thng v tinh, v n khng th t ng xc nh im lm vic ti

    u khi iu kin nh sng v nhit thay i.

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    Hnh 2.9.Mch vng iu khin in p

    b. Phng php iu khin phn hi cng sut.C th iu khin cng sut ti u bng cch cho o hm dP/dV = 0 trong iu

    khin phn hi cng sut. Nguyn tc hot ng ca phng php ny l o v khuch

    icng sut ca ti.

    u im ca phng php ny l khng cn quan tm n c tnh lm vic ca

    pin. Tuy nhin, phng php ny khuch i cng sut ca ti ch khng phi l cng

    sut ra khi ngun pin mt tri.Mc d mt b bin i c kt hp phng php MPPT c th s cho hiu qu cao

    trn di rng cc im lm vic, nhng i vi mt b bin i khng tt, ton b cng

    sut c th s khng n c ti do s tn tht nng lng. V vy, phng php ny

    i hi mt b bin i tht hon ho.

    PV DC/DC

    Rv

    Vin

    VrefMPPT

    PWM

    -

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    Chng 2. Cc b bin i bn dn trong h thng pin mt tri l m vic c lp

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    b. Phngphp mch vng dng in phn hi

    Hnh 2.10.Mch vng dng in phn hi

    Ri trong mch iu khin l b PI.

    Phng php ny ch p dng vi nhng thut ton MPPT cho i lng iu

    khin l dng in.

    2. B bin i DC/AC.H PV c lp thng s dng cc b bin i loi ngun p 1 pha.

    Hnh 2.11.B bin i DC/AC1 pha dng na cu (bn tri) v hnh cu (bn phi)Kha in t S1 v S2 c iu khin chu k ng ct theo mt lut nht nh

    to ra in p xoay chiu.in p ri trn mi t l Vdc/2. Lf v Cfc nhim v lc b

    cc thnh phn sng hi bc cao ti u ra ca b bin i v to in p xoay chiu c

    tn s mong mun. My bin p c nhim v to ra in p xoay chiu ph hp vi yu

    cu ca ti, ng thi m nhim vai tr cch ly gia ngun 1 chiu vi ti.

    Cc loi b bin i ny c th ngn chn thnh phn dng in sng hi v iu

    chnh h s cng sut nng cao cht lng in

    u im:. B bin i DC/AC 1 pha dng na cu c s kha in t t hn 1 na

    so vi b bin i DC/AC 1 pha hnh cu nn c cu trc n gin v r hn.

    PV DC/DC

    Ri

    I

    IrefMPPT

    PWM

    -

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    32

    Cu trc b bin i DC-AC dng bin p thng thng c nhc im, do s

    dng bin p thng thng nn kch thc thng ln, tn hao trn bin p kh ln,

    v hin ti gi thnh bin p cng khng nh.

    Hnh 2.12. S cu trc b nghch lu kiu Full-bridge

    Hnh 2.13.a) S cu trc b nghch lu kiu Half-bridge

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    Chng 3. Phng php d tm im l m vic ti u MPPT

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    Chng 3

    PHNG PHP D TM IM LM VIC TI U MPPT

    1. Gii thiu chungKhi mt tm PV c mc trc tip vo mt ti, im lm vic ca tm PV s

    l giao im gia ng c tnh lm vic I V v ng c tnh I V ca ti. Gi s

    nu ti l thun tr th ng c tnh ti l mt ng thng tp vi dc l 1/Rti.

    Hnh 3.1.V d tm pin mt tri c mc trc tip vi mt

    ti thun tr c th thay i gi tr in tr c.

    Hnh 3.2.ng c tnh lm vic ca pin v ca ti thun tr

    c gi tr in tr thay i c

    Ni cch khc, tr khng ca ti bm theo iu kin lm vic ca pin. Ni chung,

    im lm vic him khi ng ti v tr c cng sut ln nht, v vy n s khng sinh ra

    cng sut ln nht. Mng ngun pin mt tri thng b qu ti khi phi b cho mt lng

    cng sut thp vo thi gian nh sng yu ko di nh trong ma ng. S khng thch

    ng gia ti v cc tm pin mt tri thng lm cho ngun pin mt tri b qu ti v gy

    ra tn hao trong ton h thng. gii quyt vn ny, phng php MPPT c s

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    dng duy tr im lm vic ca ngun in pin ti ng im c cng sut ln nht

    MPP. Phng php MPPT c th xc nh chnh xc n 97% im MPP.

    Chng ny cp n c tnh lm vic I V ca moun pin mt tri v ti, s

    tng thch ca c ti v pin, phngphp iu khin MPPT; vic p dng thut ton

    MPPT iu khin b bin i DC/DC trong h thng v gii hn ca phng phpMPPT.

    2. Nguyn l dung hp tiNh ni trn, khi PV c mc trc tip vi mt ti, im lm vic ca PV s

    do c tnh tixc nh. in tr ti c xc nh nh sau:

    o

    o

    taiI

    VR (31)

    Trong : Vol in p ra, Iol dng in ra.Ti ln nht ca PV c xc nh nh sau:

    MPP

    MPPopt

    I

    VR (32)

    Trong : VMPP v IMPPl in p v dng in cc i. Khi gi tr ca ti ln nht

    khp vi gi tr Ropt th cng sut truyn t PV n ti s l cng sut ln nht. Tuy

    nhin, iu ny thng c lp v him khi khp vi thc t. Mc ch ca MPPT l

    phi hp tr khng ca ti vi tr khng ln nht ca PV.Di y l v d ca vic dung hp ti s dng mch Boost. T cng thc (2

    8):

    oin V).D1(V (3-3)

    Ta gi s rng y l b bin i l tng, cng sut trung bnh do ngun cung

    cp phi bng vi cng sut trung bnh ti hp th c.

    Pin = Pout (34)

    Khi :

    in

    o

    o

    in

    V

    V

    I

    I (35)

    T 2 cng thc (3 3) v (35) ta c:

    oin I.D1

    1I

    (36)

    Suy ra:

    tai

    2

    o

    o2

    in

    in

    in R.)D1(

    I

    V.)D1(

    I

    VR (37)

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    Hnh 3.3.Tng tr vo Rinc iu chnh bng D

    T hnh v 3.3 tr khng do PV to ra l tr khng vo Rincho b bin i. Bng

    cch iu chnh t l lm vic D, gi tr ca Rinc iu chnh gi tr ph hp vi Ropt.

    V vy, tr khng ca ti khng cn phi quan tm nhiu min l t l lm vic ca kho

    in t trong b bin i c iu chnh ng quy tc hp l.

    3. Thut ton xc nh im lm vic c cng sut ln nht MPPT Nh ni trn, im lm vic c cng sut ln nht MPP nh trn ng c

    tnh IV lun thay i di iu kin nhit v cng bc x thay i. Chng hn,

    hnh v 3.4 th hin ng c tnh lm vic I V nhng mc cng bc x khc

    nhau tng dn cng mt gi tr nhit (25oC) v hnh 3.5. th hin cc ng c tnh

    lm vic cng mt mc cng bc x nhng vi nhit tng dn.

    Hnh 3.4.ng c tnh lm vic ca pin khi cng

    bc x thay i cng mt mc nhit

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    Hnh 3.5.c tnh lm vic I V ca pin khi nhit thay i cng mt mc cng bc x

    T hai hnh v ny, ta nhn thy c s dch chuyn in p quan st c v tr

    ca im MPP. V vy im MPP cn phi dng thut ton xc nh. Thut ton ny

    l trung tm ca b iu khin MPPT.

    Thut ton MPPT c coi l mt phn khng th thiu trong h PV, c p

    dng vi mong mun nng cao hiu qu s dng ca dy pin mt tri. N c t trong

    b iu khin b bin i DC/DC.

    Cc thut ton MPPT iu khin ca b bin i DC/DC s dng nhiu tham s,

    thng l cc tham s nh dng PV, in p PV, dng ra, in p ra ca b DC/DC. Cc

    thut ton ny c so snh da theo cc tiu ch nh hiu qu nh im lm vic c

    cng sut ln nht, s lng cm bin s dng, phc tp ca h thng, tc bin

    i

    Nhn chung c rt nhiu thut ton MPPT c nghin cu v ng dng trn

    nhiu h thng. Mt phng php o in p h mch Vocca cc pin mt tri c 30 giy

    mt ln bng cch tch pin mt tri ra khi mch trong mt khong thi gian ngn. Saukhi ni mch tr li, in p pin c iu chnh ln 76% ca Voc. T l % ny ph thuc

    vo loi pin mt tri s dng. Vic thc hin phng php iu khin mch h ny n

    gin v t chi ph mc d hiu qu MPPT l thp (t 73% n 91%). Phng php tnh

    ton cng c th d on v tr ca im MPP, tuy nhin trong thc t, phng php ny

    lm vic khng hiu qu v n khng theo c nhng thay i vt l, tui th ca tm

    pin v cc nh hng bn ngoi khc nh bng ca cc vt cn Hn na, mt hc nht

    x k o cng bc x c gi thnh rt t.

    Cc thut ton s dng phng php iu khin kn mch c th cho hiu qu caohn, nn cc thut ton ny c s dng ph bin hn cho MPPT. Trong khun kh ca

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    n ny, em ch phn tch 2 phng php MPPT c ng dng rng ri v tr nn

    ph bin, quen thuc v cho c mt s hiu qu lm vic sau y:

    Phng phpnhiu lon v quan st P&O

    Phng php in dn gia tng INC

    3.1. Phng php nhiu lon v quan st P&Oy l mt phng php n gin v c s dng thng dng nht nh s n

    gin trong thut ton v vic thc hin d dng. Thut ton ny xem xt s tng, gim

    in p theo chu k tm c im lm vic c cng sut ln nht. Nu s bin thin

    ca in p lm cng sut tng ln th s bin thin tip theo s gi nguyn chiu hng

    tng hoc gim. Ngc li, nu s bin thin lm cng sut gim xung th s bin thin

    tip theo s c chiu hng thay i ngc li. Khi im lm vic c cng sut ln nht

    c xc nh trn ng cong c tnh th s bin thin in p s dao ng xung quanh(im MPP) im lm vic c cng sut ln nht .

    Hnh 3.6.Phng php tm im lm vic cng sut ln nht P&O.

    Lu thut ton:

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    Hnh 3.7.Lu thut ton Phng php P&O

    S dao ng in p lm tn hao cng sut trong h quang in, c bit nhng

    khi iu kin thi tit thay i chm hay n nh. Vn ny c th gii quyt bng cch

    iu chnh logic trong thut ton P&O l s so snh cc tham s trong hai chu k trc.

    Mt cch khc gii quyt vic hao ht cng sut quanh im MPP l gim bc tnh

    bin thin xung, nhng khi iu kin thi tit thay i, thut ton ny s tr nn chmchp hn trong vic bm theo im MPP v cng sut s b hao ht nhiu hn.

    Nh vy, nhc im chnh ca phng php ny l khng tm c chnh xc

    im lm vic c cng sut ln nht khi iu kin thi tit thay i.

    c im ca phng php ny l phng php c cu trc n gin nht nht v

    d thc hin nht, trong trng thi n nh im lm vic s dao ng xung quanh im

    MPP, gy hao ht mt phn nng lng. Phng php ny khng ph hp vi iu kin

    thitit thay i thng xuyn v t ngt.

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    3.2. Phng php in dn gia tng INCy l phng php khc phc nhng nhc im ca phng php P&O trong

    trng hp iu kin thi tit thay i t ngt. Phng php ny s dng tng in dn

    gia tng ca dypin mt tri d tm im cng sut ti u. Minh ho trn hnh v 3.8:

    Hnh 3.8.Phng php in dn gia tng

    Phng php ny c bn da trn c im l: dc ca ng c tnh pin bng

    0 ti im MPP, dc ny l dng khi bn tri im MPP, l m khi bn phi im

    MPP. Th hin nh sau:

    MPPiphnb,0dV/dP

    MPPitrnb,0dV/dP

    MPPit,0dV/dP

    V dP/dV = d(IV)/dV = I + V dI/dV I + V I / V nn ta cng c th vit li l:

    MPPiphnb,V/IV/I

    MPPitrnb,V/IV/I

    MPPit,V/IV/I

    Bng cch so snh gi tr in dn tc thi (I/V) vi gi tr in dn gia tng

    ( V/I ), Thut ton ny s tm c im lm vic c cng sut ln nht. Ti imMPP, in p chun Vref = VMPP. Mi khi im MPP c tm ra, hot ng ca pin li

    c duy tr im lm vic ny tr khi c s thay i v dng in I , s thay i ca

    dng in I th hin s thay i ca iu kin thi tit v ca im MPP.

    ln ca in dn gia tng s quyt nh nhanh chm trong vic tm ra im

    MPP. Tuy nhin khi in dn gia tng ln qu s lm cho h thng hot ng khng

    chnh xc ti im MPP v s b dao ng.

    u im chnh ca phng php ny l cho kt qu tt nht khi thi tit thay i

    nhanh. Phng php ny cng cho dao ng nh nht quanh im MPP hn phng

    php P&O. Nhc im ca phng php ny l mch iu khin phc tp. N s dng

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    2 cm bin o gi tr dng in v in p, nn chi ph lp t cao. Tuy nhin ngy

    nay vi s xut hin ca nhiu phn mm hay cc b x l lm gi thnh ca h ny

    gim i rt nhiu.

    Hnh 3.9. Lu thut ton ca phng php in dn gia tng INC

    3.1.1.Bng tng kt so snh cc phng php MPPTBng 3.1.Bng so snh thut ton MPPTThut

    ton

    MPPT

    Chi

    ph

    Thng

    s o

    S cm

    bin s

    dng

    Tc

    tnh

    ton

    Mc

    phc tp

    im

    lm vic

    tm c

    Lu

    P&OTrung

    bnh

    VPV,

    IPV2 Chm Tng

    Dao

    ng

    quanh

    im

    MPP

    S dng nhiu php

    lp; im lm vic dao

    ng quanh MPP. Khc

    phc bng phng php

    iu khin

    INC CaoVPV,

    IPV2 Chm Tng

    Ti im

    MPP

    Cho kt qu tt khi k

    thi tit thay i, trnh

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    c dao ng quanh

    MPP

    3. Phng php iu khin MPPT.Nh trnh by trn, thut ton MPPT s ra lnh cho b iu khin MPPT phi

    lm g iu chnh in p lm vic. Sau nhim v ca b iu khin MPPT l iuchnh tng gim in p lm vic v duy tr n nh mc in p lm vic ca h ngun

    pin mt tri. C 3 phng php ph bin iu khin MPPT.

    3.1. Phng php iu khin PIMPPT s o gi tr in p PV v dng PV, sau da vo thut ton MPPT

    (P&O, INC hay cc thut ton MPPT khc) tnh ton gi tr in p quy chiu Vref

    nng iu chnh in p lm vic PV ln theo Vref. Nhim v ca thut ton MPPT

    ch l nh gi tr in p Vref v vic tnh ton ny s c lp li theo chu k (thng

    khong t 1 n 10 ln ly mu trn 1 giy).

    Hnh 3.10.S khi phng php iu khin MPPT s dng b b PI

    B iu khin t l tch phn PI quy nh in p a vo b bin i DC/DC.

    B PI c nhim v b sai lch gia Vref v in p o c bng cch iu chnh h s

    ng ct D. PI c tc lm vic nhanh, cho p ng nhanh v n nh. Bn thn b iu

    khin PI c cu to t nhng thnh phn tng t Analog, nhng n c lm vic vi

    nguyn tc iu khin x l tn hiu s DSP (Processing Signal Digital) v b x l tn

    hiu s c th thc hin c nhiu nhim v khc nh xc nh im lm vic c cng

    sut ti u v vy s gim c mt s lng thnh phn trong h.

    3.1.2.Phng php iu khin trc tip.

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    Phng php iu khin ny n gin hn v ch s dng mt mch vng iu

    khin, v n thc hin nhim v iu chnh h s lm vic trong thut ton MPPT. Vic

    iu chnh h s lm vic hon ton da trn nguyn l dung hp ti trnh by mc

    3.2

    Hnh 3.11.S khi ca phng php iu khin trc tip MPPT.

    Tng tr ca PV c coi l tng tr vo b bin i. Nhc li cng thc (3 6)

    tai

    2

    o

    o2

    in

    in

    in R.)D1(I

    V

    .)D1(I

    V

    R (38)

    Trong : D l h s lm vic ca b bin i Boost.

    Hnh v 3.12. cho thy vic tng D s lm gim tng tr vo Rin, t in p lm

    vic PV s dch sang bn tri (gim i). Tng t khi gim D s lm tng Rinkhi in

    p lm vic s dch sang phi (tng ln). Thut ton MPPT (P&O, INC, v cc thut ton

    khc ) s quyt nh vic dch chuyn in p nhth no.

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    Hnh 3.12.Mi quan h gia tng tr vo ca mch Boost v h s lm vic D

    Thi gian p ng ca cc tng cng sut v ngun PV tng i chm (10 50

    mili giy tu thuc tng loi ti). Thut ton MPPT thay i h s lm vic D, sau ln

    ly mu in p v dng PV tip theo nn c thc hin sau khi h t n trng thi

    n nh trnh o phi gi tr ang trng thi chuyn tip. T l ly mu ca phng

    php ny thng t 1 n 100 ln trn 1 giy trong khi t l ly mu ca b iukhin PI

    thng nhanh hn, v vy phng php iu khin trc tip ny cho bn vng i vi

    s thay i t ngt ca ti. Tuy nhin nhn chung p ng ca h thng li chm hn.

    Phng php iu khin trc tip c th lm vic n nh i vi cc thit b nh h

    thng c trang b c quy v h thng bm nc. V t l ly mu chm nn c th s

    dng b vi iu khin gi thnh thp.

    3.2. Phng php iu khin o trc tip tn hiu ra.Phng php ny l phng php c ci tin t phng php iu khin trc

    tip trn v c u im l ch cn hai cm bin o in p v dng in ra khi b bin

    i. Phng php iu khin bng PI v phng php iu khin trc tip o tn hiu vo

    b bin i, c u im l cho php iu khin chnh xc im lm vicca pin mt tri.

    Nhng nhng cm bin vo thng cn phi c nhng cm bin khc o tn hiu ra

    trnh trng hp qu in p hay qu dng in ca ti. Nh vy hai phng php trn sfi cn n 4 cm bin hot ng c tt nht nn chi ph lp t s cao.

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    Phng php iu khin o trc tip ny o s thay i cng sut ca PV u ra

    ca b bin i v coi h s lm vic D nh mt bin iu khin. Phng php ny dng

    thut ton P&O xc nh im MPP.

    Hnh 3.13.Lu thut ton P&O dngtrong

    phng php iu khin o trc tip tn hiu ra

    c th coi D l mt bin iu khin th thut ton P&O phi c ci tin mt

    cht nhng v c bn vn l khng i. Thut ton P&O mi ny iu chnh D v o

    cng sut ra ca b bin i. Nu cng sut ra ca b bin i DC/DC tng ln, h s lm

    vic D cng s tng ln theo, v ngc li nu cng sut ra gim i th D cng s gim

    theo. Khi cng sut ra ca b bin i t n gi tr cc i th lc ny PV ang lm vic

    im MPP.

    Phng php ny ch d dng thc hin m phng vi mt b bin i l tng

    cn trong thc t vi b bin i khng phi l tng th khng th m bo rng liu gi

    tr cc i ca cng sut ra khi b bin i c tng ng vi im MPP hay khng. Mt

    nhc im khc l phng php ny ch c th thc hin vi cc tham s ca thut ton

    P&O v hon ton khng p dng cho thut ton INC.

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    4. Gii hn ca MPPT.Gii hn chnh ca MPPT l khng tc ng g n tn hiu ra trong khi xc nh

    im lm vic c cng sut ln nht. N khng th cng mt lc tc ng ln tn hiu vo

    v tn hiu ra. V vy, nu h thng cn in p ra n nh th phi s dng n c quy

    duy tr in p n nh.Mt nhc im khc ca MPPT na l: vic xc nh im lm vic c cng sut

    ti u s dng li nu nh ti khng th tiu th ht lng cng sut sinh ra. i vi h

    PV lm vic c lp c ti b gii hn bi dng v p ln nht th phng php MPPT s

    dch chuyn im lm vic ra khi im MPP v gy tn hao cng sut. Vi h ny, vic

    xc nh chnh xc dung lng ca ti l rt quan trng c th tn dng c ht dung

    lng ca cc pin mt tri. Ngc li, h PV lm vic vi li lun xc nh im lm

    vic c cng sut ln nht v nu tha cng sut h thng c th bm vo li in

    tng li nhun.Tuy nhin, hiu sut ca b bin i DC/DC thc t dng trong MPPT khng bao

    gi t c 100%. Hiu sut tng ln t phng php MPPT l rt ln nhng h thng

    pin mt tri cng cn phi tnh n tn hao cng sut do b bin i DC/DC gy ra. Cng

    phi cn nhc gia hiu sut v gi thnh. Vic phn tch tnh kinh t gia h thng pin

    mt tri vi cc h thng cung cp in khc cng nh vic tm ra cc cch thc khc

    nng cao hiu sut cho h thng pin mt tri (chng hn nh dng my theo di mt tri)

    cng l vic lm cn thit.

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    Chng 4

    B LU GI NNG LNG

    H quang in lm vic c lp cn phi c khu lu gi in nng c th phcv cho ti trong nhng thi gian thiu nng, nh sng yu hay vo ban m. C nhiu

    phng php lu tr nng lng trong h PV. Ph bin nht vn l s dng c quy lu

    tr nng lng. c quy l thit b in ho, tn tr di dng ho nng v khi c ph ti

    s dng u ni vo, ho nng c gii phng di dng in nng. B c quy gip lu

    gi in nng cha s dng v s cung cp cho b bin i DC/AC trong trng hp kh

    hu xu, tri nhiu my, ma khng cung cp nh sng. B c quy cng ng thi

    trc tip cung cp in mt chiu cho cc thit b s dng in mt chiu.

    Cu to ca c quy gm hai in cc khc nhau t trong dung dch in phn, cmng ngn cch. Do in th ca mi in cc i vi dung dch khc nhau nn gia hai

    in cc c hiu in th, nu ni vi mch ngoi c th sinh ra dng in.

    C hai loi c quy thng dng l c quy ch - axit v c quy kim.

    1. Cc loi c quy.

    1.1. c quy ch - axit

    c quy ch - axit c cu to in cc dng l ixit ch PbO2, in cc m l chxp Pb, dung dch dng l axit sulfuric H2SO4. Khi ni cc cquy vi mch ti dung

    dch s bin i thnh sulfat ch PbSO4.

    Trong qu trnh lm vic ca c quy, c nhiu phn ng ho hc xy ra. Trong qu

    trnh np, sunfat ch cc dng bin i thnh ch ixit. Cn khi c quy phng ht

    in, cc cht tch cc trn in cc dng PbO2 v trn in cc m Pb bin thnh

    PbSO4, Cn axit sunfuric H2SO4bin ht thnh nc.. Trong mt c quy c np n

    y dung lng, thng thng dung dch cha khong 36% t trng axit, hay l 25% th

    tch, cn li l nc.T l gia mt axit trong dung dch so vi mt nc gi l t trng c

    trng, l mt trong nhng thng s quan trng ca c quy, xc nh im nhit ho rn

    ca dung dch khi c quy phng ht. im nhit ho rn ca dung dch li xc nh

    kh nnglm vic ca c quy ti cc mi trng nhit khc nhau. mi trng nhit

    cng thp cng yu cu t trng c trng ca c quy phi cao. T trng c trng khi

    c quy np y thng trong phm vi 1,250 n 1,280 nhit 27 oC, ngha l mt

    dung dch ln hn nc sch 1,25 n 1,28 ln. Khi c quy phng ht in, t trng c

    trng s gim dn v 1. in p nh mc ca mt ngn c quy ch l khong 2,1 V.

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    Loi c quy ny c tui th cao, dung lng ln. c quy ch - axit c s dng

    ph bin trong h quang in lm vic c lp v n c gi thnh hp l, tnh tin dng

    v kh nng lu gi in nng t vi ting ng h n vi ngy.

    1.2. c quy kimV d loi nikel cadmium, s dng dung dch l KOH, in cc dng l

    hyroxit nikel v cc m l cadmium Cd. Khi phng in hyroxit nikel chuyn thnh

    Ni(OH)2 v cadmium thnh Cd(OH)2. Mt cht in ly khng thay i, v vy im

    ho rn rt thp. Tuy nhin loi c quy ny c gi thnh cao hn loi c quy ch - axit.

    in p nh mc ca mt ngn c quy kim l 1,2 V. in p trn cc ngn c quy

    kim c gi n nh cho n khi ngn phng in gn ht, khi in p trn ngn s

    gim t ngt. c quy nikel cadmium c th chp nhn dng np ln c gi tr bngdung lng ca c quy v c th c np tip tc lu di vi dng np c gi tr n

    1/15 gi tr dung lng ca c quy.

    2. Cc c tnh ca c quy.

    2.1. Dung lng: (k hiu l C)Thng c o bng Ampe gi (Ah), xc nh nng lng in m c quy

    phng ra vi mt gi tr dng in nht nh trong mt khong thi gian nht nh.

    Khong thi gian thng dng xc nh dung lng l 5 gi, 10 gi v 20 gi. Tng

    ng c k hiu dung lng l C5, C10, C20. Gi tr dng in o c khi xc nh dung

    lng thng bng 10% hoc 20%C

    V d: c quy c dung lng C = 100Ah s cung cp cho ti 10A trong 10 h hoc

    20A trong 5h

    2.2. in p ngng thp nht:L gi tr in p thp nht cho php trong qu trnh vn hnh c quy, xc nh

    dung lng bng khng (c quy phng ht in) ti gi tr dng phng no . Nu

    dng phng ln hn th in p c quy s gim n mc thp hn. y l gi tr do nh

    sn xut cung cp.

    2.3. in p h mch:in p gia hai cc ca c quy khi khng trong qu trnh phng cng nh qu

    trnh np. in ph mch ca c quy ch - axit ph thuc vo nhit , t trng c

    trng, thng c gi tr khong 2,1 V. Do t trng ca c quy ph thuc vo dung lng

    m c quy ang c. Khi c quy phng in, dung lng gim i nn in p khi h mch

    c quy cng gim theo.

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    3. Ch lm vic ca c quy (xt c quy ch - axit)

    3.1. Np c quy:C nhiu ch np c quy khc nhau: Ch np bnh thng, ch np hon

    thin v ch np cn bng.

    Ch np bnh thngc th bt u bt c lc no, vi dng np no, min l

    khng lm cho in p c quy vt qu mc in p sinh hi. Ch np bnh thng

    em li 80 n 90% dung lng c quy.

    Ch np hon thinbt u khi c quy np gn y, phn ln cc cht tch

    cc trong c quy tr v dng ban u ca n. Khi s cn phi tng gi tr in p

    np v dng in s suy gim dn v n khng.

    Ch np cn bngc s dng theo chu k, sau vi tun n 2 thng, vi mc

    ch l lm cho cc ngn c quy c ng u. Ch ny yu cu in p np cao hn so vi np hon thin v dng in np phi c gi n nh, trong vi gi. Thng

    thng, sau khi c quy phng kit cng cn n ch np ny.

    3.2. c quy phng: su phng in: th hin bi t l phn trm nng lng in cp cho ti

    bn ngoi so vidung lng c quy. su phng in, vi mt gi tr dng phng no

    , b hn ch bi in p ngng thp nht, thng ch cho php n 15 25% dung

    lng c quy.Mc t phng in:Khi c quy ch h mch dung lng c quy b suy

    gim chm do dng r pha cc hoc do cu to ca bn thn trong c quy. Mc t

    phng ca c quy tng theo nhit , c th t n 10 n 15%.

    3.3. Cc ch ca b ngun np c quyGm 3 ch sau y: np vi dng khng i, np vi p khng i v np ni.

    La chn ch np no cho c quy cn tu thuc vo mc ch s dng ca c quy

    (hot ng thng xuyn theo chu k hay ch hot ng theo nhu cu), tnh kinh t, thigian np lai, gi gn tui th ca c quy. Mc ch ca cc phng php np c quy ch

    yu l iu kin dng in np cui qu trnh np c quy.

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    Hnh 4.1. Cc ch np c quy

    3.4. Np vi dng khng i:y l ch np bnh thng ca c quy, s a dung lng ca c quy ln 80

    n 90% dung lng y. Vi c quy ch - axit dng np thng ly l C/10. Ch ny

    c duy tr nu in p c quy trong khong 1,8V

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    Tu thuc vo tng loi c quy s dng m c th p dng ch np ny mt

    cch lin tc hay gin on. Ch np ni lin tc c th c p dng i vi trng

    hp cn ngun d tr hot ng khi ngun xoay chiu c th b gin on. Ch np

    theo chu k khng lin tc c th p dng i vi cc thit b di ng i hi ch np

    khng lin tc thch hp.C hai phng php np trn u to cho in p n nh v gii hn dng np

    ban u ca c quy. c im ny l cn thit xc nh gi tr in p np da trn cc

    c tnh np v nhit . Vic xc nh in p np khng chnh xc c th gy ra s c

    np qu hoc np thiu. Hai phng php ny u c th s dng cho c thit b d

    phng v thit b lm vic theo chu k.

    3.6. Np ni.

    y thc cht l khng np g m gi in p n nh mc 2,25 2,3 V, thphn so vi ch np vi in p khng i. Trong ch ny c quy np no v

    khng c ti, dng vo c quy bng 0. in p ca b ngun ch c tc dng b li phn

    no dng d ca c quy nu ch khng ti ny tn ti lu di.

    Khi c quy mang ti, khong 4 trn hnh v 4.1, nu cui giai on ny c quy

    phng gn ht, ch cn 5 n 10% dung lng, th hin in p trn ngn xung di

    mc 1,8 1,95 V, phi ngt ti ra khi c quy v sau thc hin np cn bng vi dng

    ln bng C/5.

    i vi c quy kim, qu trnh xy ra cng tng t, nhng vi cc mc in pv dng in tng ng khc nhau:

    -Np vi dng khng i, ch bnh thng, Ib = C/5, khi 0,8V < Ub < 1,2V.

    -Np vi p khng i, ch hon thin, Ub = 1,51,6V .

    -Np ni, khng ti, Ub = 1,41,5V.

    -Np cn bng, dng khng i, Ib = C/2C/1,5.

    4. Lgic chuyn trng thi qu trnh np c quy t ng.

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    Hnh 4.2.S chuyn trng thi lgic qu trnh np c quyt ng

    Thit b np t ng c 4 trng thi lgic, hai trng thi iu chnh dng khng i

    v hai trng thi iu chnh in p khng i. Cc tn hiu o dng c quy Ibv in p

    c quy Ubs cho php chuyn t trng thi n sang trng thi kia, nh trn hnh v 4.2.

    Nu c quy ang trng thi h mch, Ub2= 2,3V, m mang ti th hin bi dng c quyIb< 0, th thit b s nguyn trng thi cho n khi dng gn bng 0, Ib 0A th schuyn sang ch np bnh thng vi Ib1= C/10 ri t mi chuyn sang ch np

    p khng i Ub1 = 2,4 2,45V hoc sang ch np cn bng nu Ub < 1,8V.Hnh v 4.2 cho thy lgic iu khin b np t ng l lgic trng thi, hay gi l

    lgic c nh, ch khng n gin ch l lgic t hp. Mch lgic ny c th thit k nh

    mt mch lgic lp trnh c n gin (Programmable Logic Device - PLD) hoc bng

    cc IC logic thng thng. Lu rng cc ngng in p a ra trn y phi c th

    iu chnh c, ph hp vi cc c tnh do nh sn xut cung cp cho tng loi c quy.

    5. Cc s c cn bo v ca c quy ch - axit.- Np qu:

    Nu in p np ca c quy qu cao s dn n dng vo c quy tng mnh sau khi

    c quy c np y. S c ny lm nc b phn ly thnh cc electron v lm gim tui

    th ca pin. Nu c quy thng xuyn trong tnh trng b np qu y, nhit trong c

    quy s tng ln. n mt mc no , dng in vo c quy s nhiu hn v lm nhit

    trong c quy tip tc tng ln c th ph hng c quy ch sau vi gi ng h.- Np thiu

    Hin tng np thiu thng xuyn xy ra vi c quy lm vic vi h thng pin mt

    tri do thi gian nh sng yu thng din ra trong thi gian di. Nu in p np ca c

    quy mc qu thp, dng in vo c quy khng t gi tr cn thit trc khi c quy

    c np y s lm d li mt s sunfat ch cc cc c quy, lm gim dung lng ca

    c quy, lm gim tui th ca c quy.

    - Sunfat hoDo cc tinh th ch sunfat c bin i thnh ch trong thi gian c quy np, nn

    nu sau khi phng ht, c quy lu ngy khng c np li, mt s cc tinh th ch s cn

    bm li trn cc tm bn cc. Nhng tinh th ny nh nhng lp cch ly gy tr ngi cho

    c quy khi np. y gi l hin tng sunfat ho. Hin tng ny lm dung lng ca c

    quy gim v c th lm hng c quy. trnh hin tng ny, c th p dng ch np

    cn bng c th lm ti li c quy, to s ng u ca dung dch trong cc ngn ca

    c quy.

    6. Cc tiu ch la chn c quy.Vic la chn c quy choh PV c th da vo nhng tiu ch sau y:

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    Phng su (phng su khong 70 n 80%) Dng in np/phng thp. Thi gian np v thi gian phng. n nh khi np hay phng. Thi gian t phng. Tui th Yu cu bo tr Hiu qu lu gi nng lng. Gi thnh thp.

    Cc nh sn xut c quy thng ch trng vo s chu k phng np hon chnh

    cng nh kh nng phng su ca c quy. Mc d iu ny c th gip tnh ton c

    tui th ca c quy (c quy ch - axit) trong cc h thng thng thng nh ngun cp

    nng lng lin tc hay cc phng tin s dng in, nhng i vi nhng h nng

    lng mi vn c th c nhng tnh ton sai st v tui th ca c quy. Trong h PV, hai

    vn thng quyt nh tui th ca c quy l vic np cha y v vic np thp trong

    thi gian di ca c quy.

    7. Cc thng s c trng ca c quy Power Sonic nh sau:

    7.1. c tnh phng.

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    Hnh 4.3.c tnh phng ca c quy PowerSonic

    Hnh 4.3 th hin c tnh phng ca c quy vi cc mc phng in v iu

    kin nhit khc nhau. ng c tnh phng ny ch ra mt c tnh quan trng ca c

    quy Power Sonic l in p c xu hng gi nguyn khng i trong mt khong thi

    gian di trc khi gim xung mc in p gii hn.- in p h mch ca c quy PowerSonic = 2,15V khi npno v gim xung cn1,94V khi phng hon ton.

    - bn v kh nng tch tr in: in tr trong thp v cc bn cc c cu tobng cc hp kim c bit c tc dng m bo tc t phng in thp, do kh

    nng lu tr nng lng ca c quy Sonic rt lu. Nu c m bo nhit 20 oC,

    dung lng ca c quy vn t c 60 n 70% dung lng nh mc sau 1 nm.

    Mc t phng in thay i theo nhit mi trng xung quanh: nhit

    20oC, mc t phng in l 3% mi nm, nhit thp c quy gn nh khng tphng in v nhit cao th mc t phng in tng ln.

    - Bo v phng su: m bo bn, c quy cn phi c ngt khi ti khi inp ca c quy t n mc in p ngng. Mc in p ngng l mc m ti 100%

    dung lng hu dng ca c quy c s dng hay ti vic tip tc phng l v ch

    bi khi in p gim xung di mc hu dng.

    Vic c quy ch - axit phng di mc in p ngng hay vn ni c quy vi

    ti khi in p trn cquy nh s lm gim kh nng np no ca cquy.

    Vi c quy Power-Sonic nn dng mch ngt da trn tn hiu p trnh hin

    tng phng su.

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    Hnh 4.4.Mch chng hin tng phng in su ca c quy

    - Yu cu i vi mch np c quy.Thng thng, np mt c quy PowerSonic cn mt in p mt chiu c gi

    tr cao hn gi tr in p h mch 2,15V. Tu vo cc mc np, gi tr ca pin c th

    thp hn hay cao hn 2,15V nhng sau 1 thi gian gi tr in p mi pin nn t 2,15V.B c quy Power-Sonic c th np bng cch s dng bt k phng php np

    thng thng no, tuy nhin t c dung lng v thi gian lu gi nng lng lnnht th phng php np vi p khng i, gii hn dng in cho nhiu u im hnc.

    Trong thi gian np, ch sunpht bn cc dng chuyn thnh ch oxit. Khi cquy c np no, bn cc dng to thnh ch ixit lm in p tng t ngt. Nh vy,mt in p np khng i s cho php pht hin ra lng in p tng v nh vy

    iu khin ln gi tr np.Nu in p np qu cao (np qu), dng in s chy vo c quy gy ra hin

    tng phn ly nc cht in phn, t lm gim tui th ca c quy. Khi b np quti, c quy s b nng ln. Khi nhit cao, c quy s nhn dng nhiu hon v cng nng

    hn. Hin tng ny gi l khng n nh nhit , v c th ph hu cquy trong vng 1vi gi sau .

    Nu in p np qu thp (np non), dng chy c th b dng li trc khi c quyc np y dn n ch sunphat vn cn dnh trn cc in cc v lm gim dung

    lng ca cquy.

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    7.2. Cc phng php np cho c quy.Cc phng php np c la chn tu thuc vo mc ch s dng, cn nhc v

    tnh kinh t, thi im np li, d on tn sut v su phng in, v thi gian lu trmong mun.

    Vi c quy Power Sonic, nh sn xut a ra cc phng php np sau:+ Phng php Taper.

    y l phng php n gin nht, t tn km nht. C c tnh in p khng i

    v dng in khng i c th c xy dng trong b np nh bin p, it v in tr.Nhng b np Taper thng thng gm c mt bin p nh, b chnh lu. Bin p cthit k sao cho dng c hn ch ti gi tr dng np ban u ln nht. Gi tr ny cgi cho ti khi in p v dng tng yu cu t c im m ti dng np bt ugim. Mc d phng php np ny c th np tng i nhanh nhng dng khng iv in p np c th b y ln cao v phng php ny cng nhy vi s thay i in

    p li nn rt c th dn n hin tng np qu hay np non.

    Hnh 4.5.Mch np dng bn thay i

    Hnh 4.6.c tnh np vi dng bn thay i

    + Phng php np vi dng khng i

    Phng php ny c p dng khi bit chu k phng trc tnh ton thi

    gian np v gi tr np. Phng php ny cn mch phc tp hn c c chnh xc

    gi tr dng khng i.

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    Hnh 4.7. Mch np ( trn) v c tnh np ( di) vi dng khng i

    Cn phi theo di in p np v thi gian np trnh np qu. Phng php ny

    rt hiu qu trong vic phc hi dung lng ca c quy, m rng thi gian tch tr nng

    lng hay c th np qu ti t c dung lng ca c quy. Tuy nhin phng php

    ny lai thiu nhng c trng ring bit c i hi trong mi trng in t ngy nay.

    + Phng php np p khng i

    Hnh 4.8.Mch np p/dng khng i

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    Chng 4. B lu gi nng lng

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    Hnh 4.9.c tnh np p/dng khng i

    y l phng php tt nht cho c quy PowerSonic. Tu thuc vo ng dng m

    c quy c th c np lin tc hay khng lin tc. Trong trng hp ngun cp in d

    phng c yu cu hot ng khi ngun AC b ngt, c quy cn c npni lin tc.Np vi chu trnh khng lin tc c s dng vi nhng thit b di ng c, khi

    vic np gin on l thch hp nht.

    Np dng/p khng i thc cht l p mt in p khng i ln cquy v hn

    ch dng in ban u. Cn phi t gi tr in p np theo c tnh np v nhit

    c xc nh. in p t khng chnh xc s dn n hin tng np qu hay np non.

    Phng php ny c th s dng cho c cquy s dng lin tc v cquy dng d

    phng.

    Mch np trn hnh 4.8 c s dng thm b b nhit trong qu trnh np

    m bo iu kin np ti u bt chp s thay i ca nhit xung quanh.

    - Np khi cc b cquy u ni tip.Cc c quy ch axit l nhng chui gm cc tm 2V ghp ni tip vi nhau, thng

    thng l cc loi cquy c 2,3,4 hoc 6 pin. H cquy Power-Sonic c in p ln ti

    48V hay ln hn c th c np ni tip mt cch an ton v hiu qu. Tuy nhin khi s

    lng cquy mc ni tip tng, dung lng cc cquy c th khc nhau. S khc nhau

    ny l do tui th, qu trnh tch tr nng lng, s thay i nhit .Khi mt b np in p khng i n l c ni vi mt h ni tip in p cao,

    dng in qua tt c cc cquy trong h bng nhau. Tu thuc vo cc c tnh ring bit

    ca mi b cquy, mt vi b s b np qu no trong khi mt s b cn li khc ang

    trong trng thi np hi non. Nu np c quy in p cao theo cch ny trong mt thi

    gian ko di, ngi ta khuyn co nn s dng mt b nghch lu in p u vo thp

    tng tui th ca c quy v ngin ho cc thnh phn b np.

    Nu mt pin c dung lng thp hn cc pin khc, n c th b phn cc ngc

    trong qu trnh phng cng vi nhng pin khc k c khi in p tng ca c h ln hnin p ngng.

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    Chng 4. B lu gi nng lng

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    gim tc hi gy ra do s khc bit gia cquy khc nhau, nn s dung cc

    cquy c cng tui th, cng thi gian tch tr nng lng v in p np mi cquy.

    - Np khi cc b c quy u song song.Cc cquy c mc song song vi nhau vi cng mt mc in p. Khi dng

    t b np c xu hng c chia u cho tt c cc cquy, v vy cc cquy khng cnphi ging nhau, nu cc cquy c dung lng khc nhau th dng in np cho cc

    cquy s t l vi nhau theo t l dung lng gia cc cquy (thc cht l in tr

    trong cc cquy ny t l vi nhau theo dung lng).

    Khi mc song song cc cquy c dung lng khc nhau, cn phi m bo rng

    dng in np cho mi c quy khng thay i qu nhiu .V vy mi cquy u c mc

    ni tip vi mt in tr nh to s phn phi u v dng np.

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    Chng 5. Tnh ton h thng pin mt tri l m vic c lp

    59

    Chng 5

    TNH TON H THNG PIN MT TRI LM VIC C LP

    Nhim v ca n l tnh ton h thng pin mt tri lm vic c lp cung cpin cho ti c cng sut 1kW, in p 220V, tn s 50Hz.

    1. Chn pin mt triS dng loi pin mt tri KC50T do hng Kyocera sn xut c nhng thng s c

    bn o iu kin tiu chun (1000W/m2 25oC) nh sau:

    Pmax = 60.5 W

    VMPP = 16,5 V

    IMPP = 3,6 A

    Voc = 21,06 V

    Isc = 3,8 A

    Gm Ns = 36 pin mc ni tipTa dng 20 tm pin KC50T mc ni tip nhau, khi theo cng thc (1 3), (1

    4), (15), (16) ta c:

    IMPP h = IiMPP = 3,6 A

    UMPP h = n. Ui MPP = 20. 16,5 = 330 V

    Pmax h = n. Pimax = 20.60,5 = 1210 W

    Voc h = n.Vioc = 20.21,06 = 421,2 V

    Isc h = Iisc = 3,8 A

    5.1. Xy dng m hnh pin mt triVic xy dng m hnh cc tm pin mt tri khng c g khc vi vic xy dng

    m hnh mt t bo quang in. N s dng cng mt m hnh t bo quang in. Cc

    thng s xy dng l nh nhau, ch c thng s in p (VD: in p h mch V oc) l

    khc v phi c chia cho s t bo quang in NSmc trong mt mun. V vy, ta s

    xy dng m hnh tng ng cho mt t bo quang in v t s suy ra m hnh

    ca pin mt tri.

    Hnh 5.1.S mch in tng ng ca pin quang in

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    Chng 5. Thit k v m phng h thng pin mt tri l m vic c lp

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    Mch in tng ng n gin ca mt t bo quang in l mt ngun dng

    mc song song vi mt it. Tn hiu ra ca ngun dng t l vi cng nh sng

    chiu ln t bo quang in (dng quang in Iph). Trong bng ti, t bo quang in

    khng lm vic, n ging nh mt it chng hn nh lp chuyn tip p n. N khng

    sinh ra dng cng khng sinh ra p. Tuy nhin, nu n c ni vi mt ngun cp bnngoi (in p

    ln) th n s to ra dng IDcn gi l dng it hay dng ti. it trong mch quyt

    nh c tnh I V ca t bo quang in.

    c im:

    - Dng bo ho it Ioph thuc vo nhit .- Dng quang in ILph thuc vo nhit .- in tr ni tip Rs to chnh xc gia im lm vic MPP vi in p h

    mch. N th hin s tn hao bn trong.- in tr Shunt Rshcmc song song vi it th hin c dng r qua it. Gi

    tri dng r thng rt nh v c th b qua.

    - Cng c th coi h s cht lng it n l bin tham s (thay v phi gi c nh gi tr 1 hoc 2).

    T cng thc (1 2), coi Rshrt ln nn dng in I c tnh theo cng thc sau:

    1eIII nkT)IRsv.(q

    0L (5-1)

    S ph thuc vo nhit ca dng quang in ILv dng bo ho ca it Ionh sau:

    )1TT(0K)1T(IILL (5-2)

    )nom(G

    G)T(I)1T(I nom,1SCL (5-3)

    )1T2T(

    )1T(I)2T(I0K SCSC

    (5-4)

    1T1

    T

    1nk

    )1T(V.q

    n

    3

    OO

    q

    e1T

    T).1T(II

    (5-5)

    1e

    I)1T(I

    1nkT

    )1T(qV

    )1T(SC

    ooc

    (5-6)

    T trong cc cng thc trn c tnh theo nhit K

    in tr Rs th hin gi tr in tr ca cc t bo quang in mc trong mt

    module pin:

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    Chng 5. Thit k v m phng h thng pin mt tri l m vic c lp

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    vV

    sx

    1

    dI

    dVR

    oc

    (5-7)

    1nkT

    )1T(qV

    OV

    oc

    e1nkT

    q)1T(IX

    (5-8)

    in tr Rsh c coi l rt ln nn s b qua.

    5.2. M phng c tnh lm vic ca pin mt triT s mch in tng ng trn, ta dng phn mm Matlab m phng

    c tnh lm vic ca pin KC50T khi nhit thay i t 0 n 75oC v cng bc x

    thay i t 400 n 1000W/m2. Script lp trnh m phng c trnh by phn ph lc.

    Kt qu m phng nh sau:

    Hnh 5.2.c tnh I V ( trn) v P V ( di) ca pin KC50T

    khi cng bc x thay i t 400W/m2n 1000W/m2

    Nhn xt:

    Khi cng bc x thay i t400 n 1000 W/m2, gi tr Isctng dn t 0,9A

    n 3.8 A v Voc tng dn t 19 n 22V. c tnh lm vic ca pin v im lm vic

    MPP cng x dch nhiu thay i r rt khi cng bc x thay i.Ta c th thy r rng rng khi cng nh sng cng ln th cng sut ra ca

    pin cng cng ln theo.

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    Chng 5. Thit k v m phng h thng pin mt tri l m vic c lp

    62

    Hnh 5.3.c tnh I V ( trn) v P V ( di) ca pin KC50T

    khi nhit pin thay i t 0 n 75oC

    Nhn xt:

    Khi nhit pin thay i t 25oC n 75oC, gi tr Isctng dn t 3.8 A n 3.92 A

    (khong 3%) v Vocgim t 21,5V xung 17 V. c tnh lm vic ca pin v im lm

    vic MPP cng x dch nhiu thay i r rt khi cng bc x thay i. Khi nhit

    pin cng ln th cng sut ra ca pin cng thp.

    Kim chng m phng bng Simulink

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    Chng 5. Thit k v m phng h thng pin mt tri l m vic c lp

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    Hnh 5.4.Xy dng m hnh ngun in pin mt tri trong Simulink

    Kt qu:

    Hnh 5.5.Kt qu m phng ng vi T = 25, G = 1 v T = 75, G =1

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    Chng 5. Thit k v m phng h thng pin mt tri l m vic c lp

    64

    Hnh 5.6.Kt qu m phng ng vi T=75, G = 0,75 v T = 75, G = 0,25

    Nhn xt: Kt qu m phng bng Matlab vSimulink u cho kt qu nh nhau

    2. Tnh chn b bin i DC/DC

    Pin mt tri c coi nh l mt ngun dng bm vo b bin i DC/DC. Vmc ch thit k h thng pin mt tri cung cp cho ti 1000W 220V, 50Hz nn

    cn in p 1 chiu a vo b bin i DC/AC l t 340 V n 400V. V vy ta chn b

    bin i DC/DC loi Boost (tng p). Chn cc thng s yu cu ca Boost:

    in p vo Vin = 300 330 VDC

    Dng in vo Iin= 0 n 4A

    in p ra Vout = 340 400 VDC

    Cng sut ra ln nht Pmax = 1210 W

    Tn s ng ct f = 100 kHz

    Hnh 5.7.S nguyn l mch tng p Boost

    Tnh chn cc thit b trong mch

    2.1. Tnh chn cun khng LGi tr L ca cun khng ph thuc vo s bin thin ca dng in cm ng. Gi

    tr bin thin ny khng ln qu 5% dng in cm ng v gi tr ny thng ch xut

    hin khi cng sut l ln nht (PMPP). Khi dng in gn sng bng 5% dng in

    IMPP.6,3.05,0I.05,0i LL = 0,18A

    K C

    L

    V1 V0

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    Chng 5. Thit k v m phng h thng pin mt tri l m vic c lp

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    H s lm vic ca kho in t K:

    400

    330400

    V

    VVD

    0

    in0 0,175

    L c tnh theo cng thc:

    100000.18,0175,0.330

    f.iD.VLL

    in

    = 3,2 mH

    2.2. Tnh chn t in trong mchVic tnh chn t C ph thuc vo thi gian lu gi nng lng t . Gi s ta

    chn t = 30 ms. Khi C c tnh theo cng thc sau:

    22

    3

    2

    (min)0

    2

    0

    0

    340400

    10.30.1210.2

    VV

    t.P.2C 1635,1 F

    2.3. Chn kho K v itDng qua kho K v it t nht bng vi dng in cc i qua cun cm L.

    Do : IK= I = IL = 4 A

    in p t ln K v it t nht phi bng in p ra. Nn: UK=U = 400V

    Chn loi IGBT (c gn sn it)IXSH20N60AUI c cc thng s sau:

    Bng 5.1.Cc thng s ca IGBT IXSH20N60AUIIcmax Ucemax Pemax Ucemax Uce(th) max Ige mA

    40 3 150 600 20 0.5

    Chn Dit SW04PCN020 vi cc thng s sau:

    Bng 5.2. Cc thng s ca it SW04PCN020

    Itbmax(A) Id (A) Ungmax(V)

    16 230 400

    3. La chn thut ton MPPT cho hChng 3 gii thiu 2 thut ton MPPT l P&O v INC. Phn ny s lp trnh

    m phng v so snh hai thut ton ny mt cch r rng. V mc ch trong phn ny

    ch l m phng so snh hai thut ton nn mi phn m phng ch s dng 1 mdun

    pin mu v khng ghp ni vi ti.

    Nguyn tc m phng thut ton MPPT l da trn lu thut ton ca hai

    phng php. Script lp trnh c trnh by phn ph lc.

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    Chng 5. Thit k v m phng h thng pin mt tri l m vic c lp

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    Ta m phng 2 thut ton MPPT ny vi 2 trng hp cng bc x thay i

    theo gi (cc thng s c t ra da trn cc thng k thc t lm v d m phng)

    - Ngy nng: cng bc x ln, thi tit n nh- Ngy nhiu my: cng bc x thp, thi tit thay i t ngt do nhng m

    my i qua lm che mt tri.Kt qu m phng 2 thut ton trong trng hp th nht: ngy nng, thi tit n nh

    nh sau:

    Hnh 5.8. S thay i cng bc x theothi gian trong ngy nng nng

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