bien tan da muc

7/28/2019 bien tan da muc

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LI NI U

Spht trin mnh m ca khoa hc k thut trong th k20 v 21 ngy cng

lm gia tng vai tr v tm quan trng ca lnh vc in tcng sut c trong sn xutcng nh trong i sng ca con ngi. Vit Nam, qu trnh cng nghip ha, hini ha mnh m trong nhng thp nin trli y t ra mt yu cu bc thit cn cnhng ks, nh nghin cu chuyn su vlnh vc ny. Tuy cn tng i mi mnc ta, nhng nhng khi nim v b bin i cng sut ln c nghin cu v ngdng rng ri trn th gii. Chnh v nhng li ch to ln ca b bin i cng sut ln c kim chng trong thc tcng nh thc trng l Vit Nam lnh vc ny cn chac u t nghin cu ng mc. Nn trong qu trnh thc hin n tt nghip titrng i hc Bch Khoa H Ni, di s hng dn ca thy gio TS. Phm Vit

Phng, chng em n lc c gng nghin cu v tm hiu vcc b bin i cngsut ln tiu biu hin nay. Trong , chng em c bit nhn thy nhng im u vitvt tri hn hn so vi cc b bin i cng loi ca B bin i a cp kiu moduleMMC (Modular Multilevel Converter). Do , sau mt qu trnh tm ti nghin cu, phntch, m phng v rt ra kt lun nh gi; di shng dn tn tnh ca thy gioPhm Vit Phng, chng em hon thnh n tt nghip ca mnh v ti:

Nghin cu ng dng b bin i a cp kiu module MMC (Modular MultilevelConverter).

Ni dung n ca chng em gm 6 chng:Chng 1: Tng quan vcc b bin i cng sut ln.Chng 2: Phn tch nguyn l hot ng ca b bin i a cp kiu Module.Chng 3: Phng php bin iu rng xung PWM s dng trong b bin i a cpMMC.

Chng 4: M hnh ton hc ca b bin i MMC.Chng 5: Thit k biu khin cho b bin i MMC.Chng 6: Kt qum phng.

Vi tnh cht l mt n tt nghip ngnh Tng ha, em v cc bn cgng ht sc mnh hon thnh n tt nht c th. Nhng do kinh nghim cn nhiuhn ch v do nhng thiu st phm phi trong qu trnh nghin cu, bn n cachng em chc chn cn nhiu sai st. Em xin chn thnh cm n sng gp, sa chahu ch ca thy c trong bmn Tng ha x nghip cng nghip, trng i hcBch Khoa H Ni. c bit, chng em xin gi li cm n su sc nht n thy gio TS.Phm Vit Phng, nu khng c s ch dy hng dn v gip tn tnh ca thy thchng em skhng bao gic thhon thnh n ny !


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Chng 1

TNG QUAN V B BIN I CNG SUT LN

1.1. Gii thiu vcc b bin i cng sut ln.

in tcng sut l mt chuyn ngnh ca k thut in t. in tcng sutnghin cu v ng dng cc phn tbn dn cng sut trong cc b bin i, nhm mcch bin i v khng ch ngun nng lng in c cc thng skhng thay i cthnh ngun nng lng in vi cc thng sc ththay i c cung cp cho cc

ph ti in khc nhau.

Hnh 1. 1Vtr vai tr ca in tcng sut

i vi lnh vc in ttn hiu th yu cu quan trng nht l chnh xc rimi n hiu sut. Nhng i vi in tcng sut th yu cu v hiu sut li c tln trn. in tcng sut l k thut bin i v iu khin nng lng in vi hiuqu cao nht

Ngy nay, cng ngh ch to cc phn tbn dn cng sut t c nhngtin bvt bc vi vic cho ra i nhng phn tkch thc nh gn, c khnng ngct dng in ln, chu c in p cao v gim tn hao cng sut. Cng vi l cctin bvt bc trong lnh vc l thuyt iu khin v cc phn tiu khin v dnhcc chip vi x l, vi iu khin, DSP 16 bit, 32 bit, nhanh v mnh hn trc rtnhiu. Nhng nn tng quan trng ng vai tr quyt nh n spht trin ca lnhvc in tcng sut, gp phn to ra nhiu chng loi b bin i vi nhng ng dngrng ri trong cng nghip v trong i sng. in tcng sut v ang pht trin

mnh mv tri rng trong hu khp cc lnh vc. Vi di cng sut tri rng t nh(vi


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W n vi trm W) n ln v rt ln (vi trm kW n vi chc MW). in tcng sutc ng dng rng khp tcc thit b cm tay, dn dng n cc thit bcng nghip,cc h thng trong cng nghip.

i tng chnh ca in tcng sut l cc b bin i bn dn cng sut haycn gi l cc b bin i. Nhim v ca in tcng sut l xl viu khin dngnng lng in bng cch cung cp in pvdng in dng thch hp cho cc ti. lm c iu , cn phi c nhng b bin i thch hp vi tng yu cu khcnhau ca ti. Cc b bin i trong in tcng sut thng c chia ra lm nm dngchnh. Cc b bin i lm nhim v chnh lu: bin i in xoay chiu (AC) thnh inmt chiu (DC). Cc b bin i lm nhim v nghch lu: bin i in mt chiu (DC)thnh xoay chiu (AC). Cc biu chnh in p xoay chiu AC/AC cn c gi l

cc bbm xung xoay chiu; cc biu chnh in p mt chiu DC/DC: cc bbmxung mt chiu. V cui cng l bin tn: bin i tn s tin xoay chiu c tn s f1sang tn s f2.

Hnh 1. 2 Cc dng bin i nng lng c bn trong in tcng sut

Ngy nay trong cng nghip ang xut hin ngy cng nhiu cc ng dng i hicng sut ln v hot ng c vi in p trung p. Cc ng c trung p cng sutln l mt v din hnh. Cc ng c, cc b truyn ng trung p c di cng sut trirng t0,4 MW n 40 MW v di in p t2,3 kV n 13,8 kV; tuy nhin vng lmvic ch yu ca ng c trung p l t1 MW n 4 MW vi di in p t3,3 kV n6,6 kV. ng c trung p cng sut ln c s dng trong cng nghip nhiu lnh vckhc nhau nh: s dng lm my bm trong h thng ng ng ca ngnh cng nghipha du, dng chy qut trong ngnh cng nghip xi-mng, dng lm my bm nccc trm bm, dng lm ng c ca cc my cn thp trong ngnh cng nghip sn


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xut thp, c bit l cc ng dng trong lnh vc ng st v cn nhiu ng dng khcna. Khi lm vic vi li in trung p, phng php ch ni duy nht mt van bn dncng sut trc tip vi li sgy ra rt nhiu kh khn. gii quyt vn ny, cc

nh khoa hc nghin cu v cho ra i rt nhiu cc b bin i cng sut ln nhmt cng c giao tip hu hiu gia cc ng dng yu cu cng sut ln vi li in.

Tuy nhin, cc b bin i cng sut ln khng ch gii quyt vn ca ng ctrong cng nghip m n cn c ng dng rt nhiu lnh vc khc na, c bit ltrong truyn ti in nng nh h thng truyn ti in xoay chiu thng minh (FACTS -Flexible Alternating Current Transmission System) hay h thng truyn ti in mtchiu in p cao (HVDC High-Voltage Direct Current). Hay trong mt lnh vc angrt c quan tm khc l nng lng sch, cc ngun quang in, in gi cng nh cc

pin nhin liu c ththng qua cc b bin i cng sut ln truyn ti in nng tngun cung cp n ni s dng.

Cc b bin i cng sut ln c th s dng mt trong hai dng: b bin ingun dng hoc b bin i ngun p. V cc b bin i ngun dng vn khng c sntrong thc tv li phi gi cho ngun dng bng hng snn gy ra rt nhiu kh khncho cng tc iu khin. Do nn trong thc t hin nay, ngi ta thng dng cc b

bin i cng sut ln l cc b bin i ngun p. Yu cu chung i vi cc b bini cng sut ln hin nay l:

ng ct vi tn s cao To ra in p xoay chiu c t sng hi

C cng sut ln

in p u ra cao

1.2. Tng quan vcc b bin i cng sut ln.

Ty theo cng sut, cu trc b bin i v cc yu cu ca ti m ta c cc bbin i cng sut ln khc nhau. Cc b bin i cng sut ln hin nay c thphn lmhai dng chnh l: b bin i a mc v b bin i a cp. Trong , cc b bin i acp bao gm ba dng thng gp l:b bin i c s dng my bin p, b bin icu trc ghp tng cu H (Cascaded H-bridge Converter) v b bin i a cp kiu m-un (MMC Multilevel Modular Converter). Cch phn loi b bin i cng sut lnc cho hnh di y:


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B bin i cngsut ln

B bin i a mc B bin i a cp

B bin i cdng my bin p

B bin i cu trcghp tng cu H

B bin i a cpkiu m-un

Hnh 1. 3 Tng quan b bin i cng sut ln

1.2.1. B bin i a mc

Hnh 1. 4: (a) B bin i hai mc; (b) B bin i ba mc; (c) B bin i n mc

Nhng khi nim u tin vcc b bin i a mc c nhc n tnm1975 vi khi u l cc b bin i ba mc. K t n nay, rt nhiu cu trc, c cuca b bin i a mc c pht trin ln. Tuy vy, khi nim c svcc b bini a mc vn l: s dng mt chui cc van bn dn cng vi mt vi ngun p mtchiu in p thp to ra c s bin i cng sut bng cch tng hp cc sng inp hnh thang. Mc ch sau cngchnh l t ti c mc cng sut cao hn. Tin,

pin v cc ngun nng lng ti to u c thc s dng lm cc ngun p trong ccb bin i a mc. Cch thc ng hay mcc van bn dn theo mt quy lut nh


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trc s ni thng hoc ni tt cc ngun mt chiu to ra cc mc in p khc nhautheo quy lut, t tng hp cc mc in p to ra dng in p tng cao hn u ra.

a) B bin i hai mc

Hnh 1. 5. B bin i hai mc v dng in p u ra

B bin i hai mc ch to ra c in p u ra c bin ln nht l Vd , mo tng THD tng i cao, cht lng in p cn cha tt v c cng sut nh. Tuynhin u im ca b bin i hai mc l n c cu trc n gin v diu khin.

b) B bini cu trc it kp (Diode-Clamped Mul til evel I nver ter)

S cu trc.B bin i it kp s dng cc it v tin ni tng to ra nhiu mc in pkhc nhau. Ban u, b bin i it kp vn c s dng nh mt b nghch lu bamc. Sau , n c pht trin ln thnh mt b bin i ba pha su mc nh hnh1.7. Nhn trn s cu trc ta thy mi pha ca b bin i u c ni vi ng dnmt chiu chung ta tm gi l ng dn ngun. Tuy nhin, ng dn ngun lic chia ra thnh su mc in p khc nhau bi nm t in t C1n C5nh tronghnh v. in p trn mi tin l VDCv in p trn mi van bn dn b hn chmc l VDCthng qua cc diot kp.


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Hnh 1. 6 Cu trc b bin i a mc it kp (Diode-Clamped Multilevel Inverter)

Nguyn l hot ngBng 1.1 lit k cc trng thi ng ct ca cc van bn dn v cc mc in p u ra

tng ng ca pha a . Quy c ly in p V0nhnh m ca ng dn mt chiu lbng 0. i vi cc van bn dn ta coi: trng thi 1 tc l van mv trng thi 0 tc lvan kha. Mi pha c nm cp van lin hp, mi cp van lin hp hot ng theo nguyntc: khi mt van bt k trong cp van lin hp trng thi 1 (m) th bt buc van cn li

phi trng thi 0 (ng). Nm cp van lin hp ca pha a l (Sa1, Sa1), (Sa2, Sa2), (Sa3,

Sa3), (Sa4, Sa4), (Sa5, Sa5). T bng 1.1 ta c nhn xt : trong mt pha, cc van trngthi 1 (m) lun lin k ni tip nhau, i vi mt b nghch lu su mc, lun c nmvan trng thi mtrong mi thi im.


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Bng 1. 1Bng ng ct cc van trong pha a

in p

Trng thi ng ct

Sa5 Sa4 Sa3 Sa2 Sa1 Sa5 Sa4 Sa3 Sa2 Sa1

V5=5VDC 1 1 1 1 1 0 0 0 0 0

V4=4VDC 0 1 1 1 1 1 0 0 0 0

V3=3VDC 0 0 1 1 1 1 1 0 0 0

V2=2VDC 0 0 0 1 1 1 1 1 0 0

V1=VDC 0 0 0 0 1 1 1 1 1 0

V0=0 0 0 0 0 0 1 1 1 1 1

Hnh 1. 7 Dng thin p u ra ca b nghch lu t kp

Mi in p dy u ra ca b nghch lu c dng nh trn hnh 1.2, trong Vab l tng hp in p thu c ca in p trn pha a v pha b. Kt qu ta thu cin p tng u ra l mt sng hnh thang mi mt mc c dng gn vi sng Sin.T ta c thrt ra kt lun: mt b nghch lu it kp m mc scho m mc in p

pha v (2m - 1) mc in p dy u ra.Mc d mi thit bng ct chdng kha duy nht mt mc in p l VDC

nhng trong cu trc it kp li yu cu phi c thkha c nhiu mc in p ngckhc nhau. V dtrn pha a, khi tt ccc van bn dn nhnh di t Sa1n Sa5um, it D4kha mc in p ln ti 4VDC, tng tnh vy, it D3kha mc 3VDC,it D2kha mc 2VDCv it D1kha mc VDC. Nu b nghch lu c thit k saocho mi it kha u c cng mc in p vi cc van chuyn mch, th it Dn s phi

tng ng vi n it mc ni tip nhau. Khi dn n, s lng it cn c trong


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mi pha sl (m - 1)x(m - 2). Tc l slng it kha s t l vi bnh phng s mcca b bin i it kp.

Cc ng dng tiu biu ca b bin i a mc it kp l: kt ni trung gian giang dy truyn ti in p cao mt chiu vi ng dy truyn ti xoay chiu. Dng

trong iu khin tc cho ng c cng sut ln, s dng in trung p .B VAR tnh.B bin i a mc s dng it kp c nhng u im nh sau:

Tt ccc pha dng chung mt ng dn ngun mt chiu (DC bus) vi yu cuti thiu v slng tin.

Cc tin c thc np in ttrc theo nhm. Hiu sut cao v tng thit bc ng ct tn sc bn. Phng thc iu khin n gin cho th thc Back-To-Back.Bn cnh nhng u im va ktrn, b bin i it kp cng c nhng nhc im

nh sau :

iu khin dng cng sut tc dng sl kh khn cho mi b nghch lu n biv ngun in p mt chiu trung p thng gp kh khn trong vn np t nukhng c cc biu khin.

Slng diot i hi tng i ln do b bin i s trnn rt cng knh khis mc nghch lu ln.

1.2.2. B bin i a cp

Ngy nay, cc h thng kiu phn tn v module ha ang tr thnh nhng mhnh ti u thc thi nhng yu cu t ra trong nhiu lnh vc k thut. M hnh b

bin i a cp l mt v din hnh cho phng php ny. B bin i a cp p

ng c nhng tiu chun ra nh: tng tin cy trong hot ng, ddng chunon li, sa cha bo dng v ti cu trc h thng. c bit trong trng hp xy ras c, cu trc module cho php h thng iu khin c th ddng cch ly vn , duytr hot ng an ton cho ton b h thng. Thm ch trong nhiu trng hp c th vnhnh t gn nh mc bnh thng d c xy ra s c.

S tin b gn y trong vic nng cao tnh nng dng, p ca cc thi t b chuynmch nh IGBT, GTO thc y vic nghin cu nng cp v m rng phm vi sdng ca cc b bin i a cp. Qua b bin i a cp, dng in p u ra s gn vihnh Sin.

Hnh 1. 8 Dng in p u ra ca b bin i 9 mc


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So vi cc b bin i hai mc, cc b bin i a cp cho thy r c nhngu im vt tri nh:

Cht lng sng hnh thang: B bin i a cp khng chcho in p u ra vi

mc sng hi thp hn rt nhiu m cn gim c dc in p

; do vn vtnh tng thch in tc thc gii quyt phn no. in p ca cc module: B bin i a cp cho ra nhiu bc in p nh. Do

ng sut m cc ng c phi chu khi ni chng vo biu khin nhiu ng cc gim. Trong tng lai thng qua biu chtin tin cc chin p cnc thc loi b.

Dng in xoay chiu u ra: B bin i a cp c th cung cp dng in xoaychiu t b bin dng.

Tn schuyn mch: Cc b bin i a cp c th hot ng hai tn sngct l tn sng ct c bn v tn scao PWM. Do , bng cch gim tn s

ng ct ta c th gim c tn hao do chuyn mch v v vy c tht chiu sut cao hn.Tuy nhin, cc b bin i a cp cngc mt snhc im. Mt trong nhng

nhc im chnh ca b bin i a cp l cn phi s dng n mt slng ln phntng ct bn dn v i km vi l cc h thng iu khin van. Do slm tngmc phc tp ca ton b h thng cng nh lm gia tng tn hao chung.

a. B bin i sdng my bin p

Hnh 1. 9 S cu trc b bin i ghp tng dng my bin p.

B bin i a cp ghp tng dng my bin p c th to ra c in p c bin ln thng qua my bin p, mi cp in p c b rng nh nhau. Cc my bin p y c s dng cng cc xung vung thnh p nc thang, c s bc c tnh bnghai ln s b nghch lu mt pha.


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Hnh 1. 10 Dng in p u ra 12 bc.

B bin i ghp tng dng my bin p c hai u im chnh l cho in p ra ct sng hi do qua bin p lc v c cu to n gin. Nhc im ca cu trc c sdng my bin p l kch thc ln, gi thnh cao do phi s dng my bin p v hiusut cng khng cao.

b. B bin i a cp cu trc ghp tng cu H (Cascade H-bridges I nverter)

S cu trc

S cu trc ca mt pha ca b bin i a cp ghp tng cu H c minh hatrn hnh 1.11.


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Hnh 1. 11 Cu trc mt pha ca b bin i a cp m bc

Mi ngun mt chiu c lp (Separate DC Source - SDCS ) c ni vi mtcu trc mt pha dng cu hay cn gi l cu H. Mi cu trc thnh phn nh vy cgi l mt bc ca b bin i. Mi bc ca b bin i c th to ra ba mc in p ura khc nhau l: +VDC, 0 v -VDC ty theo cc phng php t hp khc nhau ca bnvan S1, S2, S3, v S4 ni ngun mt chiu vi u ra. Khi cp van S1v S4ng thimdn dng th in p u ra l +VDC, khi cp van S2v S3ng thi mdn dngth in p u ra l -VDC. Trong trng hp mt trong hai cp van: (S1v S2 ) hoc (S3v S4 )mth in p trn u ra bng 0. Cc bc ca b bin i c ni ni tip vinhau nh trn hnh vl cu trc ca mt pha ca b bin i m bc. in p u ra cacc bc do c xp chng to nn dng sng in p u ra ca b bin i chnhl tng hp ca cc mc in p mi bc thnh phn. Quan h gia slng bc trongmt pha vi slng ngun mt chiu c lp (SDCS) c cho bi cng thc: m = 2s+ 1. Trong , m l s bc trong mt pha; s l slng ngun mt chiu c lp ca pha.


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V d v dng sngin p ca mt pha ca mt b bin i 11mc cu trc cuH vi 5 ngun mt chiu c lp c cho trn hnh 1.12: in p u ra ca mt phac tnh theo cng thc Va-n = Va1 + Va2 + Va3 + Va4 + Va5.

Hnh 1. 12 thin p u ra ca b bin i a cp cu trc ghp tng cu H

Chng ta c th k ra nhng u nhc im chnh ca b bin i a cp cu trc ghptng cu H nh sau. Vu im:

S mc in p u ra ca b bin i ln hn slng ngun mt chiu clp hn hai ln: m=2s+1

Phng php cu trc theo kiu m-un cho php qu trnh iu khin trnn ddng, nhanh hn v t tn km hn.

Tuy nhin, b bin i cu trc ghp tng cu H vn cn c nhc im l mi bcca b bin i yu cu phi c mt ngun mt chiu c lp (SDCS). Do nhng ng


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dng ca cu trc loi ny b hn ch trong nhng sn phm c sn cc ngun mtchiu c lp.

c. B bin i a cp kiu m-un (Modular M ulti level Converter - MMC)

S cu trc

SM

SM

SM

SM

SM

SM

Vdc

L L L

L L L

L

L

L

n module

thnh phn

Usu

Usv

Usw

iu

iv

iw

SM

SM

SM

SM

SM

SM

SM

SM

SM

SM

SM

SM

Hnh 1. 13 . Cu trc b bin i a cp kiu module (MMC)

Hnh 1. 14Module thnh phn c cu trc na cu


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Hnh 1. 15Module thnh phn c cu trc cu

Trong nm 2010, h thng HVDC PLUS da trn mt k thut bin i a cpc gi l b bin i a cp kiu m-un (MMC) ca Siemens ln u tin c

a vo s dng trong thc t. Gn nh cng lc , ABB nng cp sn phm HVDCLight ca hcng da trn mt cng nghtng t chnh l b bin i a cp kium-un (MMC). MMC c xy dng tcc module thnh phn ng nht nhng li ckhnng iu khin c lp c tng module. Cc module thnh phn trong MMC cthc cu trc na cu nh trn hnh 1.13, hoc c cu trc cu nh trn hnh 1.14. Vicu trc na cu, mi module c khnng cung cp in p u ra hai mc l +VDChoc 0 V; vi cu trc cu, mi module c th cung cp ba mc in p u ra l +VDC,0, v VDC. iu c ngha l b bin i c th hot ng nh mt ngun p c iu

khin vi mt s lng ln cc mc in p c th cung cp cho u ra. ng thi,MMC cng lm gim ng kcc sng hi bc cao.

MMC l cu trc m, c khnng cho php mrng. Mc in p ca MMC phthuc vo s lng ca cc m-un thnh phn; thm ch MMC c th c s dngtrong cc h thng truyn ti in nng siu cao p. Trong cu trc ca MMC khng thchin theo cch mc ni tip mt lot cc van bn dn vi nhau, do c thtrnh cs phc tp trong qu trnh iu khin ng bha cc van. ng thi li c th gimtn tht ca b bin i xung mc rt thp, ch khong 1 %. iu ny c c l do tnsng ct thp trong mi m-un thnh phn v in p trn cc van trong mi m-uncng mc thp. Mi m-un thnh phn s thc hin vic ng ct cc thi imkhc nhau do b bin i c tht c hiu sut cao cng nh lm gim mosng hi.


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Hnh 1. 16. V d vdng in p pha AC ca b MMC 9 mc

B bin i MMC c nhng u im ni bt nh:

Tnh kh dng cao, c cu trc m un da trn s kt ni nhiu b bin i (SM)

ng nht, s dng chung mt bus DC.

i vi cc ng dng ni li th bbin i ni MMC c kh nng b cng sut

phn khng, loi b sng hi, ng thi cn bng ti.

Do khng dng ti ngun mt chiu c lp cung cp cho tng SM nn gi thnh

v kch thc thit b gim ,vic tho lp cng s d dng hn

Tuy vy n cng c nhc im ring :

Khi cu trc cng m rng th s lng van bn dn cng s tng ln

TNG KT:

B bin i a mc kiu module (Modular Multilevel Converter - MMC) l mttrong nhng b bin i trung v cao p tin tin, hiu qu nht t c mc tiu cth bin i cng sut ln m khng cn phi s dng n my bin p. Nm 1981,

Alesina v Venturini xut cu trc nhnh kiu module theo phng php minhnh l s xp chng ca nhiu b ngun. Marquardt v Lesnicar a ra nhng khinim c bn nht v b bin i a mc kiu module (MMC) cng vi l nguyn tchot ng cng nh kim nghim khnng vn hnh, cht lng vn hnh ca MMCtrong iu kin l tng. Allebrod, Hamerski v Marquardt i su vo nghin cu vcc ng dng ca MMC trong h thng cao p dng in mt chiu HVDC nhm giiquyt cc vn v hiu sut v tn tht trong h thng. V Siemens l nh tin

phong trong lnh vc ny khi a vo vn hnh h thng HVDC PLUS ng dng cngnghMMC. Theo bo co th cu trc ca h thng HVDC PLUS c hn 200 m-unthnh phn mi nhnh, v c th cung cp cng sut ln ti 400 MVA.


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Vi yu cu thc hin n tt nghip trong khong thi gian nh trc, chngem quyt nh la chn ti l Nghin cu ng dng ca b bin i a cp kiumodule. Trong ch trng nghin cu, tm hiu v m phng hot ng ca b bini a mc kiu moduleMMC v nhng tin bv nhng ng dng rng ri ca cu

trc ny trong thc t.Ni dung n ca em gm 6 chng, tm tt ni dung v mc ch ca mi chngem xin trnh by khi qut nh sau:

Chng 1: Tng quan vcc b bin i cng sut ln. Ni dung ca chng emmun nu ra nhu cu hin nay ca cc b bin i cng sut ln trong trongnghip cng nh trong truyn ti in. Sau l gii thiu chung v phn loi cc

b bin i cng sut ln ang c s dng ph bin hin nay. c bit, tem mun a ra sso snh thy c nhng u im cng nh nhc imca b bin i a bc kiu module MMC so vi cc b bin i khc v l do tmhiu nghin cu v b MMC.

Chng 2: Phn tch nguyn l hot ng ca b bin i kiu module. Trongchng ny em i su vo tm hiu v phn tch nguyn l hot ng ca b bini MMC bao gm hai dng cu trc: b bin i na cu v b bin i cu. T, em tm hiu vcc ng dng ca b bin i MMC trong thc t.

Chng 3: Phng php bin iu rng xung PWM s dng trong b bin iMMC. Trong chng ny, em nu ra v phn tch cc phng php PWM c sdng cho b bin i MMC trong thc t, phn tch nguyn l, u nhc im. T, em quyt nh chn phng php PWM dch pha ng dng iu khintrong n. Cc kt qum phng bng phn mm PSCAD c trnh by.

Chng 4: M hnh ton hc ca b bin i MMC. Trong chng ny em trnhby qu trnh m hnh ha b bin i MMC di dng m hnh ton hc. Kt qucui cng thu c m hnh ton hc ca MMC phc vcho cng tc iukhin chng sau.

Chng 5: Thit k biu khin cho MMC. Tm hnh ton hc xy dngc em a ra cu trc iu khin cho b MMC. Sau , em ra ba

phng n iu khin l: iu khin trung bnh, iu khin cn bng cho tng SMv iu khin cn bng nhnh.

Chng 6: Kt qum phng. Trnh by cc thng sm phng v cc kt qum phng t phn mm PSCAD.


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Chng 2

PHN TCH NGUYN L HOT NG CA B

BIN I A CP KIU MODULE

2.1. Cu trc ca b bin i a cp kiu module - MMC

Mi pha ca b bin i MMC c thc nhiu module thnh phn (Submodule- SM) c ghp tng vi nhau. Cu trc ca MMC c chia lm hai nhnh, nhnh

trn v nhnh di mi nhnh u c in p . gia dng cc cun cm L

cn bng gia hai nhnh v lc bt sng hi.

SM 4u

SM 2u

SM 1u

SM 5u

SM 7u

SM 8u

Vdc

L L L

L L L

L

L

L

Usu

Usv

Usw

iu

iv

iw

SM 3u

SM 6u

SM 4v

SM 2v

SM 1v

SM 5v

SM 7v

SM 8v

SM 3v

SM 6v

SM 4w

SM 2w

SM 1w

SM 5w

SM 7w

SM 8w

SM 3w

SM 6w

ipu

inu

Hnh 2. 1. Cu trc mch lc ca b bin i MMC [13].

B bin i ghp tng a cp kiu module (MMC) c thphn thnh hai dng

l : b bin i na cu ni sao kp (DSCC Double Star Chopper-cell) v b bini cu ni sao kp (Double Star Bride-cell). Hai loi trn cng l loi b bin i a

DCV

2


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cp, in p ra u c dng mc, cu trc mch u l cc module thnh phn (SM)ghp tng vi nhau nn dgy ra nhm ln gia hai loi. Da vo cu trc s mchkhc nhau m ta c thphn bit hai loi ny trong h MMC:

B bin i a mc na cu ni sao kp DSCC :Trong cu trc ny, mi b SM bao gm hai IGBT v mt tin, c dng nh hnhvdi y :

Hnh 2. 2 . Cu trc na cu ni sao kp ca MMC .

B bin i a mc cu ni sao kp DSBC :

Trong cu trc ny, mi b SM bao gm 4 IGBT v mt tin, dng nh hnh vdi y:

Hnh 2. 3. Cu trc cu ni sao kp ca MMC [15].

2.2. Nguyn l hot ng ca MMC

2.2.1. B bin i na cu-DSCC

B bin i na cu hay cn gi l chopper-cell bao gm hai IGBT v mt tin mt chiu ging nh hnh 2.2.Nguyn l hot ng ca b bin i na cu:


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ia> 0

ia< 0

Hnh 2. 4. Nguyn l hot ng ca b bin i na cu [17].

Trng hp 1: IGBT1 on, IGBT2 off. Nu dng in ia> 0 th in p u raca module thnh phn (SM) VX = VC, dng in chy qua it D1, qua C v ra khiSM. Nu dng in ia< 0 th in p u ra ca b bin i VX = VC, dng in vo tnhnh m ca SM, qua tC v qua IGBT1 ra ngoi. Nh vy, ia> 0 th in p tngun DC np vo cho tin v c gi tr bng gi tr VC ca tin, ia< 0 th inp u ra VX = VC do tin xnng lng vo ti trong qu trnh vn hnh.

Trng hp 2: IGBT1 off, IGBT2 on. K cdng in ia> 0 hay ia< 0 th inp u ra ca SM cng l gi tr VX= 0 do dng in i vo tnhnh dng ca SM

i qua IGBT2 on v ra ngoi(ia> 0)hay dng in i vo tnhnh m ca SM, i quait D2 v ra ngoi(ia< 0). Nh vy, trong trng hp ny in p t ngun hay t tiu b ngn mch qua tin, iu ny khin cho gi trin p u ra ca b bini lun c gi tr VX = 0.

Bng 2. 1 Trng thi ng ct ca IGBT trong b bin i na cu.

Mode T2 T1 ia Vju dVC/dt

1 OFF ON >0 VCju >0

2 OFF ON


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2.2.2. B bin i cu-DSBC

Trong cu trc ny, mi b SM bao gm 4 IGBT v mt tin, dng nh hnhv2.3.Nguyn l hot ng ca b bin i MMC kiu DSBC nh sau:

ia> 0

ia< 0

Hnh 2. 5. Nguyn l hot ng b bin i cu .

Tng tnh b bin i na cu, vic ng ct IGBT v in p ra ca bbin i cu c th hin theo bng 2.2.

Bng 2. 2 Trng thi ng ct ca IGBT trong b bin i cu.

Mode T1 T2 T3 T4 Vx(Ia> 0) Vx(Ia


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1 ON OFF OFF ON VC -VC

2 OFF ON ON OFF VC -VC

3 ON OFF ON OFF 0 0

4 OFF ON OFF ON 0 0

2.3. ng dng ca MMC

Trong nm 2003, Marquardt v cng s a ra mch bin i cng sutkhc l B bin i a mc cu trc modular (MMC) v nguyn l hot ng c

bn ca n [10],[11]. Cc ng dng ca MMC bao gm:

MMC thch hp nht vi cc ng dng in p cao v cng sut ln bi v

chng kt ni cc thit b theo mt chui m khng cn n thnh phn ng

b.

Nng cao in p v cng sut.

Ph hp cho iu khin ng c di in p trung bnh v cao v dnh

qut gi, my bm, my nn kh, nhng loi ti m c momen t lbnh

phng vi tc quay.

Nn tng c bn cho b bin i ni li.

V cn rt nhiu ng dng khc trong cng nghip nh h thng BESS(

Battery Energy Storage System), HVDC...

2.3.1. ng dng ca b bin i na cu

Nh ni trn, cu trc ca mch DSCC l s kt hp ca cu trc sao kpvi cc b bin i l na cu nh hnh 2.2. DSCC gm nhiu b bin i na cughp tng vi nhau hai nhnh trn v di. DSCC s dng hai cun cm c gi trin cm bng nhau c t trn hai nhnh m v dng.


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Hnh 2. 6. S h thngng dng DSCC dng iu khin ng c [19].

Trong thc tcc ng dng ca n l:

DSCC thng c ng dng cho iu khin ng c v in p ra xoay chiuca n c th kt ni trc tip vi ng c. N thng c ng dng iu

khin ng c c in p trung bnh, h thng truyn ti dng mt chiu in

p cao (HVDC), v h thng Back-To-Back (BTB) t c sthay i tn

s gia hai h thng in vi tn skhc nhau, hoc lin kt khng ng b

gia hai h thng in vi cng mt di tn s(hnh 2.7).

DSCC cn c ng dng cho h thng b bin i ni li trao i cng

sut phn khng vi li in (hnh 2.8).

2.3.2. ng dng ca b bin i cu

Khc vi DSCC, DSBC c cu trc b bin i c ni hnh sao, gm ccu xoay chiu ca nhiu b bin i cu cng c ghp tng vi nhau hai nhnhtrn v di. DSBC s dng hai cun cm ring bit, ph hp vi h thng bin inng lng (PCS) cho vic ti to cc ngun ti nguyn nh nng lng gi v mttri. DSBC cn c th hot ng nh mt b chuyn i tn s ba pha sang mt phatrc tip.

200 V

50 Hz

190 V

15 kW

380 V

15 kW

IG IM

iu

iS

vDC

iDC

DSCC

vu

p, q

(5%)

LAC

1:2

PDC

400 V


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2.3.3. ng dng ca MMC cho h thng HVDC-Plus

H thng in p cao mt chiu HVDC (High Voltage Direct Current) l hthng truyn ti s dng dng mt chiu cho phn ln qu trnh truyn ti in nng,n c nhiu u im vi cc h thng xoay chiu ph bin: gi thnh thp hn, cho

php t tn hao hn. HVDC cho php truyn ti cng sut gia cc h thng cung cpin xoay chiu khng ng b, hoc gia cc mng li in c tn skhc nhau.Hin nay HVDC c dng rng ri nhiu nc trn th gii. Gn y, tp onSIEMENS c nhng bc tin trong vic ci tin HVDC, trong a b bin imodular MMC dng IGBT thay thcho cc b bin i cng sut cin dngThysistor l ng k nht.

Hnh 2. 7. ng dng ca HVDC Plus.

Trong nguyn l hot ng ca HVDC Plus c trnh bynh hnh vdiy:

Hnh 2. 8. Nguyn l hot ng chnh ca HVDC Plus .


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C th thy MMC ng mt vai tr rt quan trng trong h thng HVDC Plus.Nhc cc b bin i kt hp vi cc biu khin m khi kt ni cc h thngtruyn ti in p cao chng ta c thyn tm v cht lng, gim thiu tn hao, m

bo tc p ng nhanh v ddng iu chnh nhiu mc in p. Khi ng dng

MMC vo HVDC Plus ta c cu trc nh sau:

Hnh 2. 9 .S lp rp HVDC Plus sdng MMC [23].

Hnh 2. 10 .H thng HVDC thc tca SIEMEN [24].


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