[123doc.vn] Bao Cao Nghien Cuu Cong Huong Tan So Thap Trong He Thong Dien Ssr

Nghin cu Cng hng tn s thp

Thc hin: L Quc Anh i

MC LC

MC LC .................................................................................................................. iCHNG 1: TNG QUAN ..................................................................................... 1

1.1. TI SAO LI LP BO CO NY? ........................................................... 11.2. NI DUNG BO CO ................................................................................... 1

CHNG 2: QU IN T TRONG H THNG IN .......................... 12.1. TNG QUAN .................................................................................................. 12.2. HIN TNG CNG HNG DI NG B - SSR ............................ 1

2.2.1. Gii thiu v SSR ..................................................................................... 12.2.2. Nguyn nhn gy ra hin tng SSR ....................................................... 22.2.3. Cc yu t nh hng n SSR ................................................................ 3

2.3. CC PHNG PHP PHN TCH CNG HNG TN S THP ....... 4CHNG 3: PHNG PHP LUN M PHNG, TNH TON SSR BNG PHN MM EMTP-RV ........................................................................................... 6

3.1. GII THIU V CHNG TRNH EMTP-RV ........................................... 63.2. PHNG PHP LUN M PHNG H THNG IN ........................... 73.3. PHNG PHP LUN M PHNG NGUN IN ................................. 8

3.3.1. M phng ngun in l i tng nghin cu ....................................... 83.3.2. M phng cc ngun in cn li .......................................................... 11

3.4. PHNG PHP LUN M PHNG MY BIN P .............................. 133.4.1. My bin p 2 cun dy .......................................................................... 133.4.2. My bin p 3 cun dy .......................................................................... 15

3.5. PHNG PHP LUN M PHNG NG DY ................................ 173.5.1. M hnh ng dy thng s tp trung .................................................. 173.5.2. M hnh ng dy thng s ri ............................................................ 173.5.3. M hnh Cp in ................................................................................... 20

3.6. PHNG PHP LUN M PHNG KHNG IN ............................... 203.6.1. Khng 3 pha ............................................................................................ 213.6.2. Khng 1 pha ............................................................................................ 213.6.3. Khng trung tnh ..................................................................................... 21

3.7. PHNG PHP LUN M PHNG BVCQA ....................................... 223.8. PHNG PHP LUN M PHNG T B DC 500kV ....................... 223.9. PHNG PHP LUN TNH TON SSR ................................................ 22

CHNG 4: KT QU TNH TON CNG HNG TN S THP -SSR ................................................................................................................................... 24

4.1. KT QU TNH TON ............................................................................... 25

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Thc hin: L Quc Anh ii

4.1.1. Khng b dc ng dy ....................................................................... 254.1.2. B dc 30% ............................................................................................ 254.1.3. B dc 50% ............................................................................................ 264.1.4. B dc 70% ............................................................................................ 264.1.5. Tng hp kt qu .................................................................................... 27

4.2. tNH TON PHN TCH SAI S ............................................................... 274.3. CC BIN PHP HN CH NH HNG CA SSR ............................ 304.4. KT LUN V KIN NGH ....................................................................... 31

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Thc hin: L Quc Anh 1

CHNG 1: TNG QUAN

1.1. TI SAO LI LP BO CO NY?

1.2. NI DUNG BO CO

Bo co ny bao gm nhng ni dung sau:

Xy dng phng php lun m phng, tnh ton h thng:

Phng php m phng cc phn t h thng. Phng php tnh ton.

Kt qu tnh ton: tnh ton cng hng tn s thp. nh gi nh hng ca hin tng cng hng di ng b:

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CHNG 2: QU IN T TRONG H THNG IN

2.1. TNG QUAN

Trong h thng in c rt nhiu phn t khc nhau, cc phn t li c phn ng khc nhau i vi cng mt hin tng. Vic m phng ton b cc phn t s lm mt rt nhiu thi gian v lm khi lng tnh ton tr nn qu ln. Mt khc, c rt nhiu phn t m vic m phng chng hay khng s khng nh hng n kt qu tnh ton cui cng. Do , cn phi la chn chnh xc cc phn t khi m phng v m hnh thch hp cho tng phn t .

Cc qu trnh qu in t xut pht t cc nguyn nhn khc nhau c th rt khc nhau v bn cht, cng nh khong tn s dao ng. Chnh v vy, vic m phng tnh ton cn m bo vic p ng khong tn s ph hp vi qu trnh qu ang nghin cu.

Cc qu trnh qu in t c th phn loi thnh cc nhm tn s nh trnh by trong Bng 1.

Bng 1: Phn loi cc nhm tn s ca cc qu trnh qu in t

Nhm Khong tn s dao ng Dng sng Loi qu in p

1 0,1 Hz 3 kHz Dao ng tn s thp Qu in p tm thi

2 50/60 Hz 20 kHz Sng chm Qu in p ng ct

3 10 kHz 3 MHz Sng nhanh Qu in p st

4 100 kHz 50 MHz Sng cc nhanh Qu in p phng in lp li

Hin tng cng hng di ng b (Subsynchronous resonance SSR) l hin tng ng c cc c im ring c IEEE nh ngha nh sau: Cng hng di ng b - SSR l iu kin vn hnh ca h thng m trao i nng lng gia h thng vi turbine my pht mt hoc mt vi tn s di tn s ng b.

2.2. HIN TNG CNG HNG DI NG B - SSR

2.2.1. Gii thiu v SSR

Cng hng di ng b - cng hng tn s thp l iu kin c th tn ti trong h thng, h thng c tn s dao ng ring di tn s cng nghip. Dng in lc ny c 2 thnh phn: thnh phn th nht tn s cng nghip v

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thnh phn cn li ph thuc vo c tnh ca h thng. Biu thc dng in cho mch R-L-C ni tip nh sau:

( ) ( )21 1 2 2( ) sin sinti t K A t Be t = + + + (1) Trong qun dy stator my pht cng c mt dng in tng t dng in

trong cng thc (1) v phn x vo rotor my pht, qu trnh vt l ny c m t trong ma trn truyn Park. Cc tn s khc nhau c gi l cc tn s khng ng b. Cc dng in khng ng b ny sinh ra m men xon trc ln rotor tubin-my pht lm rotor dao ng tn s khng ng b.

S xut hin ca m men xon khng ng b trn trc rotor gy ra mt s vn , v bn thn trc tubin-my pht c kiu dao ng t nhin, ci m bt k h thng khi trc quay no cng c. Vn xy ra l m men xon khng ng b li trung hp vi mt kiu dao ng t nhin no ca trc, v vy trc s dao ng tn s t nhin ny, i khi l vi bin ln. Hin tng ny c gi l cng hng khng ng b, n c th gy ra hin tng mi ca kim loi ca trc v c th lm hng hoc ph hy trc.

2.2.2. Nguyn nhn gy ra hin tng SSR

C rt nhiu kiu tng tc gia h thng v my pht c th dn ti cng hng di ng b. Mt s trong chng c bn c nh ngha, chng ta cp y 3 trong s chng c nhng c im ring nh sau:

in cm my pht: nh hng ca in cm my pht b gy ra bi hin tng t kch ca h thng. in tr ca rotor, nhn t phn ng c

gi tr m. H thng cng th hin in tr tng t nhng vi gi tr

dng. Tuy nhin, nu in tr m ca my pht c gi tr ln hn in

tr dng ca h thng mt tn s t nhin ca h thng, th s c

gi cc dng in khng ng b. iu kin ny c bit nh nh

hng ca in cm my pht.

Tng tc xon: xut hin khi m men xon khng ng b in cm trong my pht lin quan mt thit ti 1 trong cc kiu t nhin xon ca

trc tubine-my pht. Khi hin tng ny xy ra, rotor dao ng s to ra

cc thnh phn in p cm ng c cc tn s di ng b v siu

ng b. Tuy nhin, in p tn s di ng b s gy ra m men xon

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di ng b. Nu m men xon ny bng hoc vt qu mc cn c kh

vn c ca h thng quay, th h thng s t kch.

M men xon qu : m men xon qu l kt qu ca nhiu lon h thng. Nhiu lon h thng gy ra nhng thay i t ngt trong h

thng, kt qu ca nhng thay i ny l dng in s c xu hng dao

ng cc tn s t nhin ca h thng. Trong h thng truyn ti khng

c t b dc, cc qu trnh qu ny thng qu dc, hin tng s

suy gim v zero vi hng s thi gian ph thuc vo t s L/R. Vi

mng c t b dc, dng qu s c th dng tng t nh cng thc

(1), v s bao gm 1 hoc nhiu tn s dao ng ph thuc vo cc thnh

phn C cng nh L v R ca h thng. V d s ch c 1 tn s t nhin

nh th hin trong cng thc (1), nhng vi h thng c nhiu t b dc

s c nhiu tn s i ng b. Nu bt k mt tn s no trong

trung khp vi 1 kiu t nhin ca trc tubine-my pht, th s c th c

m men xon cc i ln t l thun thun vi cng ca dng in

dao ng. Dng in t s c ngn mch c th sinh ra m men xon

trc rt ln c lc s c cng nh khi s c c loi tr. Trong

thc t c th c rt nhiu tn s di ng b v phn tch chng l

rt phc tp.

Tuy nhin, hin tng SSR ch thc s xy ra khi c t b dc t gn my pht. Chnh v vy, khi tnh ton dung lng b dc ngoi yu t tng hiu qu truyn ti cng sut, i khi cn b gii hn bi hin tng SSR.

Trong 3 kiu tng tc trn m t, 2 kiu u c th coi nh l cc iu kin nhiu lon nh. Kiu th 3 c coi l khng phi nhiu lon nh v c tnh phi tuyn cn phi phn tch.

2.2.3. Cc yu t nh hng n SSR

Trong qu trnh nghin cu hin tng SSR, 2 thng s thng c s dng nh gi mc nh hng l: bin ca m men xon v trt ca cc khi quay.

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C rt nhiu yu t c th nh hng n ln bin m men xon v trt ca cc khi quay trong qu trnh xy ra hin tng SSR. Trong , cc yu t c nh hng quan trng nht gm c:

Dung lng b dc trn ng dy di. Thng s ca my pht in xy ra hin tng SSR. Thi gian loi tr s c.

2.3. CC PHNG PHP PHN TCH CNG HNG TN S THP

C nhiu phng php c th s dng nghin cu SSR. Cc phng php thng dng nht l:

Phng php qut tn s: phng php c s dng rng ri bc M cho t nht l phn tch s b cc vn SSR, v thng dng ring cho

nghin cu tc ng t pht in cm. Phng php ny tnh ton in

tr v in khng tng ng (l hm ca tn s) nhn vo h thng t

qun Stator ca my pht no . Ti nhng tn s m in cm bng 0

v in tr m, dao ng t kch tn s c th xy ra do tc ng t

in cm pht.

Phng php qut tn s cng cung cp cc thng tin cho bit kh nng c th xy ra cc vn tng tc xon v m men xon qu . Cc vn

ny c th xut hin nu c vic cng hng dc hoc cc tiu in

khng, nhng hin tng lin quan rt mt thit vi 1 trong cc tn s

xon trc.

Gii hn ca phng php l cch nhn in khng t mt im c nh trn h thng, thng l trn cc cun dy stator my pht. Qu trnh

thc hin phi c lp li cho cc iu kin khc nhau ca h thng

cc im my pht khc nhau cn quan tm.

Phng php tr ring: phng php ny cung cp thm thng tin lin quan n hot ng h thng. Kiu phn tch ny c thc hin vi m

hnh h thng v my pht trong mt h tuyn tnh ha. Kt qu cho bit

c tn s dao ng cng nh mc cn ca mi tn s.

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Tr ring c nh ngha trong khi nim ca cc ng thc tuyn tnh ha h thng c vit theo dng chun sau:

A xx Bu= + (2)

Sau , tr ring c nh nga khi gii ma trn: [ ]det 0U A = (3)

Trong c gi l tr ring. S dng phn mm EMTP: EMTP l chng trnh s. Khng nh cc

chng trnh n nh qu , thng ch m hnh theo th t thun coi

nh h thng c cn bng tuyt i, EMTP, m hnh h thng hon ton

theo 3 pha mt cch chi tit hn nhiu. Ngoi ra, EMTP cn cho php

m hnh phi tuyn cc phn t h thng phc tp. Do , s ph hp vi

phn tch cc vn m men xon qu SSR.

Trong phn sau y s ln lt trinh by chi tit phng php lun m phng, tnh ton v kt qu tnh ton hin tng cng hng di ng b s dng phn mm EMTP-RV.

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CHNG 3: PHNG PHP LUN M PHNG, TNH TON SSR BNG PHN MM EMTP-RV

3.1. GII THIU V CHNG TRNH EMTP-RV

Nh trnh by, EMTP l chng trnh tnh ton QTQT. y l chng trnh my tnh m phng qu in t, in c v h thng iu khin trong h thng in nhiu pha.

EMTP-RV l phin bn mi ca EMTP c pht trin bi Development Coordination Group (DCG) vi cc thnh vin: American Electric Power Corporation, CEA Technologies, CRIEPI of Japan, lectricit de France, EPRI, Hydro One Networks, Hydro-Qubec, US Bureau of Reclamation v Western Area Power Administration. Chng trnh c th c s dng cho phn ln cc tnh ton ch tnh cng nh m phng cc QTQ vi thi gian khong vi giy. Thng thng EMTP c dng cho 2 mc ch chnh sau:

H tr trong thit k v la chn thng s cho cc phn t trong h thng in, c dng cho cc bi ton phi hp cch in, la chn thng s

nh mc ca thit b, la chn cc thit b bo v, thit k h thng iu

khin, nh gi cht lng in nng, tnh ton sng hi v.v

Tnh ton kim tra cc vn ang tn ti trong h thng in.

Di y l cc tnh ton, m phng c trng EMTP-RV c th thc hin:

Qu in p kh quyn. Qu in p thao tc Qu in p tm thi Phi hp cch in in t cng sut v FACTS Thit k h thng iu khin Cc bi ton v cht lng in nng Cng hng gia phn t b ngang v b dc

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Cng hng st t Khi ng ng c Phn tch ch xc lp ca h thng khng i xng Li in phn phi v ngun phn phi M hnh h thng ng v ph ti Cc bi ton bo v h thng in

EMTPRV c th la chn thc hin cc m phng sau:

Tnh phn b cng sut (Load-Flow): Phn b cng sut c tnh cho h thng nhiu pha v khng i xng. Kt qu c s dng lm d liu

cho thng s iu kin u (bin) cho m phng qu .

Ch xc lp (Steady-state): Tnh ton iu kin u cho m phng theo thi gian.

M phng thi gian (Time-domain): Tnh ton qu trnh qu theo thi gian.

3.2. PHNG PHP LUN M PHNG H THNG IN

Nh cp, u tin phi xc nh c phm vi nghin cu v sau l xc nh gii hn m phng. Khng mt phng php m phng no c th p ng tt c cc nghin cu.

Phm vi m phng SSR ni chung l m phng ng vic tng tc gia ng c ng b v h thng trong khong tn s di ng b t 0 n 50Hz, cc phn t c m phng nh sau:

Ngun in. M phng my bin p. ng dy truyn ti v cc phn t bao gm: t b dc, khng b ngang,

MOV.

M phng ph ti in.

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3.3. PHNG PHP LUN M PHNG NGUN IN

Do c im ring ca cng hng tn s thp l s cng hng gia my pht v phn cn li ca h thng, v vy m phng ngun in trong nghin cu SSR c chia lm 2 i tng sau:

M phng my pht l i tng nghin cu: i vi ngun in ny cn phi c m phng k lng c 2 phn:

Phn in gm cc in khng dc trc, ngang trc, cc hng s thi gian.

Phn c chnh l phn m phng cc c tnh c hc nh momen, tc , ca turbin-my pht.

M phng cc ngun in cn li: ch cn m phng phn in vi cc thng s in hc c bn.

3.3.1. M phng ngun in l i tng nghin cu

Nh cp, m phng ngun in l i tng nghin cu cn c m phng k c 2 phn: phn in v phn c.

Phn in m phng y cc in khng doc trc v ngang trc. Cc d liu cn thit c trnh by trong bng sau:

Bng 2: Thng s phn in m phng my pht

K hiu Tn ca thng s n v Gi tr

m phng

Gi tr tham kho

ULL in p pha pha u cc my pht kV 22 f Tn s Hz 50 T u dy phn ng Y

Sm Cng sut nh mc MVA 600 Thng s v in khng

R 0.0045 Xl Tn tht phn ng pu 0.14 0.14 X0 in khng th t khng pu 0.12 0.20 X2 in khng th t nghch pu 0.2 0.20

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Xd in khng ng b dc trc pu 1.65 1.65 Xq in khng ng b ngang trc pu 1.59 1.59 Xd in khng qu dc trc pu 0.25 0.25 Xq in khng qu ngang trc pu 0.46 0.46 Xd in khng siu qu dc trc pu 0.2 0.20 Xq in khng siu qu ngang trc pu 0.2 0.20

Thng s v hng s thi gian (HSTG) Td0 HSTG h mch dc trc qu s 4.5 4.5 Tq0 HSTG h mch ngang trc qu s 0.55 0.55 Td0 HSTG h mch dc trc siu qu s 0.04 0.04 Tq0 HSTG h mch ngang trc siu qu s 0.09 0.09

M phng phn c ca my pht vi cc hng s, m men v cc h s cn l c im ring ca tnh ton cng hng tn s thp. M phng c tnh c hc ca my pht kho st c ngha rt ln n kt qu tnh ton cui cng. M hnh ca my pht gm c: 2 turbine cao p, 2 turbine h p, rotor my pht v kch t c th hin trong hnh sau:

Khi quay th n c m t bng cng thc theo nh lut newton th 2 nh sau:

ur /exrm

rm rm t bine gen cdJ D HSP T T

dt + + =

Trong :

J: l ma trn m men qun tnh (moment of inertia). rm: l vector tc quay tuyt i.

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HSP: l ma trn h s cng - hng s n hi (stiffness coefficients hoc spring constant).

D: l ma trn h s cn. Tturbine: l vector m men xon t ln khi turbine (Tm1, Tm2, Tm3 v

Tm4).

Tgen/exc: l vector m men xon in t ca my pht v kch t (Tm5 v Tm6).

M men qun tnh v h s cng l nhng s liu thng thng c cung cp t thit k.

S n hi ca cc phn trn trc gia cc khi i-1 v i to ra m men xon t l vi gc xon rm i - rm i-1. H s t l l h s cng hay hng s n hi HSPi i-1. M men xon n hi (Tspring) ny tc ng theo hng t khi i-1 n i, do :

Tspring i-1 = - Tspring i =HSPi-1 I (rm i - rm i-1)

3 thnh phn cn vi cc h s gm c: t cn tc tuyt (absolute speed damping) - DSDi ca khi I, cn tng h (mutual damping) DSMi i +1 v DSMi i -1. M men xon cn (Tdamping i) t ln khi I c tnh nh sau:

Tdamping i = DSDi rm i + DSDi-1 i (rm i - rm i-1) + DSDi i+1 (rm i - rm i+1)

Mt h s cn khc l t cn khng ng tc (speed deviation self damping) DSRi t 1 m men xon (Ti) c tnh nh sau:

Ti = DSRi (rm i bm)

Trong : bm l tc quay c bn (ng b).

Trong thc t, rt kh xc nh c cc gi tr thc cho cc h s cn ny. Tuy nhin, cc m men xon trn nh hng rt t ln m men xon cc i trong qu trnh qu .

Cc m men xon ny c tnh nh sau;

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Trong : exciter l tc quay ca khi kch t.

D liu cn thit c trnh by trong bng sau:

Bng 3: Thng s phn c m phng my pht

Khi m phng

Moomen qun tnh

Cn khng ng tc

Cn tng h

Hng s n hi

(106)

Cn tc tuyt i

J DSR DSM HSP DSD Kg.m2/rad N.m.s/rad N.m.s/rad N.m /rad N.m.s/rad

Kch t 58.27 46.51 0 5.953 0 Rotor 7423.5 5926.96 0 132.85 0 Turbin 1 13091.06 10451.96 0 67.96 0 Turbin 2 2102.8 1678.89 0 0 0

3.3.2. M phng cc ngun in cn li

i vi cc nghin cu qu in t trong mt vi chu k u tin (trong c QTQ ng ct) hon ton c th s dng m hnh ngun gm mt sc ng v in khng siu qu (trang 251-ti liu 25).

Do , trong tnh ton TRV, c th s dng m hnh ngun V with impedance l mt ngun iu ha c t trc l mt tng tr:

( ) os( t+ ); =2 fmv t V c = (1)

+

120kV /_0

VwZ2

Hnh 1: M hnh V with impedance

D liu cn cho m hnh ny gm c:

Source: cc thng s v bin , tn s v gc pha ca ngun. Impedane: tng tr ngun (s dng in khng siu qu ).

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Ngoi ra, thit lp cc d liu ban u (in p, gc pha) cn phi tnh ton ch xc lp (load flow) vi vic s dng phn t Load-Flow Bus. Phn t ny c t ti nt ngun m n thit lp d liu, v c mt trong 3 loi nt sau:

Nt cn bng(slack bus): Nt ph ti (PQ bus): Nt in p (PV bus):

Hnh 2: M hnh phn t Load-Flow Bus

Nt cn bng: Cc thng s khai bo cho nt ny bao gm:

Frequency: tn s ca ngun (Hz). Controlled voltage: Bin in p ti nt m ngun ny ni vo (V, kV,

MV, kVRMS, kVRMSLL).

Controlled phase: gc pha in p ti nt t thit b LF.

Nt ph ti: Cc thng s khai bo cho nt ny bao gm:

Frequency: tn s ca ti (Hz). Voltage: Bin in p pha ti nt m ti ny ni vo (V, kV, MV,

kVRMS, kVRMSLL). in p ny ch dng khi to cho bc lp

u tin.

Phase: gi tr ban u gc pha in p ti nt t thit b LF. P,Q: cng sut tc dng v phn khng ca ti ti nt.

Thit b ny c th ly gi tr khi to t ln gii LoadFlow trc, nu c.

Nt in p

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Cc thng s khai bo cho nt ny bao gm:

Frequency: tn s ca ngun (Hz). Controlled voltage: Bin in ti nt m ngun ny ni vo (V, kV,

MV, kVRMS, kVRMSLL).

Phase: gi tr ban u gc pha in p ti nt t thit b LF. Controlled type: dng iu chnh in p: in p pha-t P: cng sut tc dng pht. Qmin, Qmax: gii hn cng sut phn khng ca ngun.

3.4. PHNG PHP LUN M PHNG MY BIN P

Hu ht cc hin tng qu in t tn s thp u b nh hng rt ln bi phn ng ca li st t trong my bin p (gm c hin tng bo ha t v tr t). Do , khi m phng my bin p tnh ton QTQ ng ct (bao gm tnh ton gi tr TRV), vic m phng cc hin tng bo ha t v tr t l rt quan trng (trang 201-ti liu 24).

3.4.1. My bin p 2 cun dy

m phng my bin p 2 cun dy trong tnh ton gi tr TRV, thng s dng m hnh nh minh ha trong Hnh 3 . Cc khi xfmr A, B v C (my bin p tng ng 1 pha) c cu to bao gm 1 my bin p l tng, cc tng tr pha s cp v th cp, nhnh t ha c biu din bng mt in tr Rmag v 1 in cm phi tuyn Lmag (Hnh 4)

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Hnh 3: s khi mt my bin p 3 pha 2 cun dy

Hnh 4: s mch ca ca 1 khi xfmr (my bin p tng ng 1 pha)

Cc thng s cn thit cho mt m hnh my bin p bao gm:

D liu c bn Nominal power: Cng sut nh mc Sn Nominal frequency: tn s f Winding 1 voltage: in p nh mc Un1 ca cun dy 1, in p dy. Winding 2 voltage: in p nh mc Un2 ca cun dy 2, in p dy. Winding R: R Winding X: X Winding 1 R: R1, in tr cun dy 1 Winding 1 X: X1, in khng cun dy 1

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Winding Impedance on winding 1: T s tng tr ca cun dy 1 trn tng tr tng Z1/Z

Winding 2 R: R2, in tr cun dy 2 khi Z1/Z khng c khai bo Winding 2 X: X2, in khng cun dy 2 khi Z1/Z khng c khai bo D liu t ha (di dng bng s liu) Current magnitude: dng in imag trong c tnh bo ha (A). Flux magnitude: t thng trong c tnh bo ha t (Wb). Magnetization resistance: in tr t ha Rmag

D liu c th cho di dng Pu hoc s dng n v c tn ( v H).

3.4.2. My bin p 3 cun dy

i vi vic m phng my bin p 3 cun dy, thng s dng m hnh nh minh ha trong Hnh 5. C th s dng m hnh c sn ny hoc thay i u ni (t u dy) bn trong s khi ca thit b ny. Cc khi xfmr A, B v C c cu to bao gm 1 my bin p l tng, cc tng tr pha s cp, th cp v cun th 3, nhnh t ha c biu din bng mt in tr Rmag v 1 in cm phi tuyn Lmag (Hnh 6).

Hnh 5: s khi mt my bin p 3 pha 3 cun dy

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Hnh 6: s mch ca mt khi xfmr

D liu c bn: Nominal frequency: tn s f Nominal power for winding 1: Sn1 cng sut nh mc cun dy 1 Nominal power for winding 2: Sn1 cng sut nh mc cun dy 2 Nominal power for winding 3: Sn1 cng sut nh mc cun dy 3 Winding 1 voltage: in p nh mc Un1 ca cun dy 1. Winding 2 voltage: in p nh mc Un2 ca cun dy 2. Winding 3 voltage: in p nh mc Un3 ca cun dy 3. Winding 1 R: in tr cun dy 1 R1 Winding 2 R: in tr cun dy 2 R2 Winding 3 R: in tr cun dy 3 R3 Winding 1 X: in khng cun dy 1 X1 Winding 2 X: in khng cun dy 2 X2 Winding 3 X: in khng cun dy 3 X3 D liu t ha (di dng bng s liu) Current magnitude: dng in imag trong c tnh bo ha (A), Flux magnitude: t thng trong c tnh bo ha t (Wb), Magnetization resistance: in tr t ha Rmag.

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3.5. PHNG PHP LUN M PHNG NG DY

Chng trnh EMTP-RV cho php m phng rt a dng cc loi ng dy v cp, gm c:

M hnh thng s tp trung: c s dng cho m phng ng dy 220kV hoc ng dy ngn.

M hnh thng s ri. M hnh thng s hng M hnh thng s ph thuc tn s: c s dng cho m phng ng

dy 500kV.

M hnh Cp in.

3.5.1. M hnh ng dy thng s tp trung

Trong EMTP-RV, cc thng s tp trung ca m hnh ng dy c th c tnh ton thng qua hm LINE DATA (c trnh by c th phn sau). Tuy nhin, cc thng s ny cng c th c nhp trc tip thng qua vic s dng m hnh:

PI 3-phase PI line 3-phase

Hnh 7: m hnh ng dy thng s tp trung

D liu cn thit cho 2 m hnh ny c bn l ging nhau, gm c:

R-L-C: Cc thng s R, L, C ca ng dy, c th s dng dng ma trn c cc phn t tng h hoc cho di dng thnh phn i xng (th t

thun v khng).

3.5.2. M hnh ng dy thng s ri

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Th vin lines.ctf cung cp cc m hnh thng s ri ca ng dy trn khng (m-pha):

Tham s hng (Constant Parameter-CP Line) Tham s ph thuc tn s (Frequency Dependent-FD Line)

M hnh FD Line cc tham s khai bo c xy dng bng hm Line Data trong cng th vin.

LINE DATA

Hnh 8: m hnh cho php thit lp d liu ng dy

D liu u vo cho module ny bao gm:

D liu v dy dn (Conductor Data) Module: cho php khai bo cc dng d liu cn tnh (line model hoc

Line Parameters)

Line Model: to ra m hnh ng dy cho cc bi ton ch xc lp v m phng thi gian.

Line Parameters: tnh in tr, in khng, v in dung ca dy dn. Unit: xc nh n v s dng cho d liu bao gm h SI hoc h English Input opton: la chn cch khai bo s b tr v s liu dy dn. Number of conductors: s lng dy dn. Conductor data table: bng khai bo thng s dy dn: Wire: s hiu dy (s th t quy c) Phase number: l s th t pha ca dy dn. Nu c nhiu hn 1 dy dn

c cng s th t pha ngha l cc dy dn ny c ni song song.

DC resistance: in tr 1 chiu n v ca dy dn.

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Outside diameter: ng knh ngoi dy dn Horizontal distance: ta x ca dy dn so vi 1 mc chung (x=0) Vertical Height at tower (VHtower): cao treo dy so vi mt t. Vertical Height at Midspan (VHmid): cao ti im vng thp nht ca ng dy.

Additional data for Wire: cho php khai bo d liu chi tit thm v tng dy dn.

Skin effect corection: hiu chnh theo hiu ng b mt: Thick/Diam: khai bo t s T/D (Thickness/Diameter) None: b qua hiu ng b mt Solid conductor: coi gn ng dy dn c. Galloway-Wedephol: s dng cng thc hiu chnh Galloway- Wedephol

(ch p dng vi Line Parameters).

Hnh 9: thng s dy dn

Bundle conductor: khai bo i vi dy phn pha Number of conductor in the bundle: s dy dn cng 1 pha. Spacing: khong cch gia hai dy lin k. Angular position (ANPHA) l gc ca dy u tin.

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Hnh 10: s b tr dy phn pha

Model: la chn m hnh ng dy (phn b ri hay tp trung) Line length: chiu di ng dy

3.5.3. M hnh Cp in

Cp in cng c th c m phng thng qua cc m hnh c sn chung vi ng dy. Tuy nhin, vi m hnh cp in c thng s ph thuc vo tn s, cc thng s c tnh ton qua hm c cha trong phn t CAPBLE DATA trong cng th vin.

CABLE DATA

Hnh 11: m hnh CABLE DATA

Tng t i vi LINE DATA, CABLE DATA c nhp cc thng s u vo cn thit tnh ton cc thng s cn thit cho mt tuyn cp.

3.6. PHNG PHP LUN M PHNG KHNG IN

Hin nay, cc khng in b ngang trn h thng in 500kV Vit Nam c 2 loi:

Loi 3 pha: 3 pha nm trong cng 1 khi, do phi m phng s h cm gia cc khng. Thng cho cc khng nh hn 130MVAr

Loi 1 pha: 3 khng 1 pha c t ring r, do vy khng cn m phng mi lin h cm ng gia cc khng (h cm). Thng cho cc khng

ln hn 130MVAr.

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Cc loi khng ny cn phi c m phng theo cc cch khc nhau.

3.6.1. Khng 3 pha

S liu cn nhp vo: R1, X1, R0, X0

S dng m phng sau:

Hnh 12: M hnh khng 3 pha

Trong , cun khng chnh s dng m hnh:

+

RL5

Hnh 13: M hnh phn t RL coupled 3 phase

3.6.2. Khng 1 pha

S liu cn nhp vo: R, X

S dng m phng gn ging khng 3 pha, tuy nhin cun khng chnh s dng m hnh:

+1/1

RL6

Hnh 14: M hnh phn t RL

3.6.3. Khng trung tnh

M hnh s dng cng loi vi m hnh khng chnh ca khng 1 pha.

+

+

+

+

+

+

RX C

+

R

L4RX

+

a b c

C

+1

R

1

Rex + Ceart

Trung tnh

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3.7. PHNG PHP LUN M PHNG BVCQA

BVCQA c lp t trc cc thit b hn ch mt s dng qu in p xung di mc cch in ca thit b. Trong ch vn hnh bnh thng, BVCQA gn nh c h mch, khi xy ra qu p BVCQA s hn ch in p xung mc an ton, v s quay v trng thi ban u khi ht qu trnh qu in p. Chnh v vy m BVCQA c in tr rt ln khi h thng vn hnh bnh thng, v in tr nh khi qu in p qu , chnh l do BVCQA c c tnh V-I phi tuyn. Chnh v vy, c tnh V-I ca BVCQA cn c m phng khi tnh ton cc QTQT.

Hnh 15: c tnh tiu biu ca mt BVCQA (ZnO hoc MOV)

Gi tr ca cc im thuc ng c tnh ny c nhp vo i tng Nonliner Data.

Data functionZnO

Hnh 16: M hnh Nonliner Data

Cc thng s cn thit cho m hnh

Desired Voltage rating: in p nh mc ca BVCQA D liu cc im c tnh BVCQA

3.8. PHNG PHP LUN M PHNG T B DC 500KV

3.9. PHNG PHP LUN TNH TON SSR

Trong phn ny s trnh by chi tit phng php lun tnh ton SSR.

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Phn mm s dng cho m phng: EMTP-RV Ch vn hnh ca h thng: Tnh ton SSR s thc hin i vi ch

vn hnh ca h thng

Ph ti cc i. S c ngn mch: 3 pha u pha N.Mng Dng trc t b dc (nu

c):

Thi gian loi tr s c: 50ms. Phn tch nhy: khi m phng h thng bng phn mm EMTP_RV,

cc thng s a vo lun c nhng sai s nht nh so vi thc t, v rt

nhiu nguyn nhn:

Nguyn nhn ch quan: do cng tc thu thp s liu cha y , do nhp s liu cha chnh xc,..

Nguyn nhn khch quan: do tin cc cng trnh, do s thay i thng s cc phn t so vi khi thit k, thi cng,

Ngoi ra, trong qu trnh tnh ton, gim thi gian tnh ton, mt s yu t nh hng n kt qu tnh ton c th c gi thit.

Chnh v vy, trong mt s trng hp xc nh trng hp xu nht ca h thng, ta c th tnh ton thm vi vic thm vo cc thng s

nhy. Trong trng hp ny cn xem xt thm cc yu t sau:

Cc dng ngn mch khc nhau. V tr xy ra ngn mch. Vic ct khng ng thi gia cc cc ca my ct. Thi gian loi tr s c.

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CHNG 4: KT QU TNH TON CNG HNG TN S THP -SSR

Tnh ton c thc hin cho 1 t my Nhit in Mng Dng 1, ch ph ti cc i nm 2016 vi cc trng hp sau:

Khng t t b dc. t t b dc so vi tng khng ca ng dy: XL = 25 x 0,2425 =

6,062 . Vi cc dung lng b dc:

B 30% tng ng: XC = 1,819 B 50% tng ng: XC = 3,031 , B 70% tng ng: XC = 4,244

Cc thng s c theo di kt qu nh gi nh hng ca cng hng tn s thp gm c:

M men xon gia cc khi quay. Tc quay ca cc khi so vi tc ng b.

Gi tr tnh ton c tnh theo h n v c bn c lit k trong bng sau:

STT Thng s K hiu n v Gi tr

1 in p U kV 22

2 Cng sut S MVA 600

3 Dng in I A 15746

4 in khng Z Ohm 0,8067

5 Tn s f Hz 50

6 S cc Rotor P 2

7 Tn s gc Rad/s 314,16

8 Moomen xon T MegaN.m 1,91

Kt qu tnh ton c trnh by trong cc mc di y.

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4.1. KT QU TNH TON

4.1.1. Khng b dc ng dy

4.1.2. B dc 30%

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4.1.3. B dc 50%

4.1.4. B dc 70%

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4.1.5. Tng hp kt qu

Thng s n v Khng b B 30% B 50% B 70%

M men xon cc

i

HP-LP Pu 0,26 0,30 0,27 0,28 LP-Gen Pu 2,79 2,93 2,99 2,89 Gen-Exi Pu 1,39 1,52 1,51 1,46

H s trt %

HP % 9,01 10,35 9,50 9,94 LP % 1,86 2,08 2,03 1,90 Gen % 1,04 1,20 1,27 1,12 Exi % 2,40 2,33 2,38 2,41

Qua kt qu tnh ton nhn thy rng:

C hin tng SSR xy ra sau khi s c ngn mch c loi tr ti khu vc TTN.Mng Dng.

M men xon ln nht tnh ton c xut hin gia 2 khi Tuabin h p v m pht. V m men xon nh nht tnh ton c xut hin gia 2

khi Tuabin cao p v Tuabin h p.

Khi tuabin cao p s xy ra trt nhiu nht v khi my pht t trt nht.

Trng hp khng b, nh hng ca hin tng SSR l nh nht.

Nh vy, sau khi s c ngn mch c loi tr ti TTN.Mng Dng c th xy ra hin tng SSR. Phn t b nh hng ln nht l on trc ni gia tuabin h p v my pht. Tuy nhin, trong trng hp khng b dc, nh hng l nh nht.

4.2. TNH TON PHN TCH SAI S

Phn sau y s ln lt tnh ton vi nhng kch bn khc nhau xoay quanh trng hp c s - ngn mch 3 pha, trc t N.Mng Dng, thi gian loi tr s c 50ms, b 30%.

Kt qu tnh ton vi cc trng hp ngn mch ti cc v tr khc nhau c trnh by trong bng sau:

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Thng s n v Trc t MD Sau t

MD Sau t

QN Trc t

QN

M men xon cc

i


H s trt %

HP % 10,35 7,01 7,03 4,28 LP % 2,08 1,46 2,34 1,71 Gen % 1,20 1,09 1,42 1,25 Exi % 2,33 2,32 2,41 2,39

Kt qu tnh ton vi cc trng hp loi ngn mch khc nhau c trnh by trong bng sau:

Thng s n v Ngn

mch 3 pha

Ngn mch 2

pha

Ngn mch 1

pha

Ngn mch 2

pha chm t

M men xon cc

i


H s trt %

HP % 10,35 3,01 9,25 7,94 LP % 2,08 0,85 1,32 1,43 Gen % 1,20 0,54 0,71 0,78 Exi % 2,33 0,97 1,31 1,49

Kt qu tnh ton trng hp xem xt n vic ct khng ng b gia cc cc ca my ct.

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0 10 20 30 40 50 60 70 80 90 1000

0.5

1

1.5

2

2.5

3

3.5

Simulation number

yABSBAR

min: 0.3183 max: 0.58793

min: 1.4702 max: 1.51

min: 0.21309 max: 0.31996

min: 1.185 max: 1.5857

min: 2.4739 max: 3.4616

min: 0.20661 max: 0.31601

Tm_1_SM1@machine_min@1Tm_2_SM1@machine_min@1Tm_3_SM1@machine_min@1Tm_1_SM1@machine_max@1Tm_2_SM1@machine_max@1Tm_3_SM1@machine_max@1

Kt qu tnh ton trng hp xem xt n thi gian loi tr s c khc nhau..

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Thng s n v 40ms 50ms 60ms 70ms

M men xon cc

i


H s trt %

HP % 8,05 10,35 8,37 11,07 LP % 1,58 2,08 2,11 1,90 Gen % 1,01 1,20 1,33 1,56 Exi % 1,84 2,33 2,57 2,58

4.3. CC BIN PHP HN CH NH HNG CA SSR

Hin nay c nhiu phng php phng nga v hn ch nh hng ca hin tng SSR n h thng trc tuabine-my pht. Trong bo gm:

Hn ch in p t ln t b dc bng MOV hoc khe h phng in. Hin nay, cc t b dc trn cc cung on D 500kV Vit Nam u

c c 2 thit b nay.

C lp dng in gy ra hin tng SSR i vo trong my pht. Ci t cc b lc c lp SSR i qua im trung tnh ni t ca MBA

tng p.

Ci t cc b SEDCs (Suplemental Excitation Controls) cn cc tn s SSR.

Cc rowle m men xon cng vi thit k TCSC : Gim st tc trc v lc ra cc dng m men xon. i vi cc dng m men xon cn c ng cong bin -thi gian

xc nh vic ngt t my hoc ng dy c lp khi s tc

ng t ngun kch thch.

Cng ngh thng dng nht cho nh a ch li ca SSR. Cc bin php khc hn ch nh : iu khin kch t ph.

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Lc tnh : dc theo mi pha ca my pht chnh. Lc ng : s dng b lc tun hon thysistor. Bypass t b dc vi khe h ph thp.

4.4. KT LUN V KIN NGH

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