luẬn Án tiẾn sỸ nÂng cao chuẤt lƯỢng Ổn ĐỊnh hỆ thỐng ĐiỆn (pss)
DESCRIPTION
Kỹ thuật điều khiển bền vững (robust) đã đƣợc ứng dụng cho thiết kế hệ điều khiển HTĐ từ cuối những năm 1980. Sự tiện lợi chính của kỹ thuật này mang lại là một công cụ tự nhiên để mô phỏng thành công những trạng thái không ổn định của nhà máy điệnTRANSCRIPT
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B GIO DC V O TO I HC THI NGUYN
Nguyn Hin Trung
NG DNG L THUYT TI U RH NNG CAO CHT LNG
CA H IU KHIN N NH H THNG IN PSS
Chuyn ngnh: T ng ha M s: 62.52.60.01
LUN N TIN S K THUT
NGI HNG DN KHOA HC:
1. PGS.TS Nguyn Don Phc
2. PGS.TS Nguyn Nh Hin
Thi Nguyn 2012
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LI CAM OAN
Ti xin cam oan y l cng trnh nghin cu ca ring ti da trn s hng
dn ca tp th cc nh khoa hc v cc ti liu tham kho trch dn. Kt qu
nghin cu l trung thc v cha cng b trn bt c mt cng trnh no khc.
Thi Nguyn, ngy 13 thng 8 nm 2012
Nghin cu sinh
Nguyn Hin Trung
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LI CM N
Trong qu trnh lm lun n, ti nhn c nhiu kin ng gp t cc
thy gio, c gio, cc anh ch v cc bn ng nghip.
Ti xin by t lng bit n n PGS.TS Nguyn Don Phc v PGS.TS
Nguyn Nh Hin dnh tm huyt hng dn ti trong sut thi gian qua.
Ti xin chn thnh cm n cc thy gio, c gio b mn T ng ha
Khoa in Trng i hc K thut cng nghip, cc ng nghip b mn H
thng in Khoa in Trng i hc K thut cng nghip v gia nh c
nhng kin ng gp qu bu v to cc iu kin thun li cho ti trong qu trnh
hon thnh lun n.
Ti xin chn thnh cm n Phng qun l o to sau i hc Trng i
hc K thut cng nghip; chn thnh cm n b mn iu khin t ng Vin
in Trng i hc Bch Khoa H Ni, trung tm nghin cu trin khai cng
ngh cao trng i hc Bch Khoa H Ni to nhng iu kin thun li ti
hon thnh lun n ny.
Tc gi lun n
Nguyn Hin Trung
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MC LC
LI CAM OAN ii
LI CM N iii
MC LC iv
DANH MC CC K HIU vii
DANH MC CC CH VIT TT x
DANH MC CC HNH V, TH xi
M U 1
1. Tnh cp thit, ngha l lun v thc tin ca ti 1
2. Mc ch nghin cu ca ti 2
3. i tng v phm vi nghin cu 2
4. Phng php nghin cu 3
5. Nhng ng gp mi ca lun n 3
6. Cu trc ca lun n 3
Chng 1. TNG QUAN 6
1.1. Gii thiu cu trc h thng in 6
1.2. iu khin h thng in 8
1.2.1. Nhim v iu khin HT 8
1.2.2. Cu trc iu khin HT 10
1.3. Vn dao ng gc ti trong HT 16
1.3.1. nh ngha gc ti (gc rotor) 16
1.3.2. Cn bng cng sut trong HT 18
1.3.3. Nguyn nhn gy ra dao ng gc ti 18
1.4. B n nh HT - PSS 21
1.5. Nhng vn nghin cu v PSS 22
1.5.1. Mt s phng php thit k PSS 22
1.5.2. Cc cng trnh nghin cu v PSS 25
1.6. Hng nghin cu ca lun n 26
1.7. Kt lun chng 1 27
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Chng 2. M HNH TON CA TRM PHT IN TRONG H
THNG IN 28
2.1. M hnh my pht in ng b 30
2.1.1. Phng trnh biu din trn h trc to dq0 31
2.1.2. Phng trnh vi mch t tuyn tnh 34
2.2. M hnh kch t v b iu chnh in p 36
2.3. M hnh turbine v b iu chnh tc 39
2.3.1. M hnh turbine 39
2.3.2. M hnh b iu tc 41
2.4. M hnh ca h my pht kt ni vi HT 42
2.4.1. Phng trnh rng buc in p trong h n v tng i 42
2.4.2. M hnh multitimescale ca h my pht kt ni vi HT (m hnh
bc 8) 43
2.4.3. M hnh b qua qu stator ca h my pht kt ni vi HT (m
hnh bc 6) 45
2.4.4. M hnh two-axis ca h my pht kt ni vi HT (m hnh bc 4) 47
2.4.5. M hnh fluxdecay ca h my pht kt ni vi HT (bc 3) 48
2.4.6. M men damping 50
2.5. Kt lun chng 2 51
Chng 3. PHN TCH B N NH H THNG IN PSS 52
3.1. Xy dng m hnh tn hiu nh ca h my pht kt ni vi HT 52
3.2. Phn tch nh hng ca PSS i vi n nh tn hiu nh 58
3.3. Phn tch cu trc cc PSS 63
3.3.1. PSS u vo n PSS1A 63
3.3.2. PSS u vo kp 64
3.4. Phn tch cc thnh phn trong PSS2A/2B 68
3.4.1. Tn hiu tc 68
3.4.2. Tn hiu cng sut in 69
3.4.3. Tn hiu cng sut c 69
3.4.4. B pha v la chn tn hiu n nh 70
3.4.5. Khu gii hn in p u cc 70
3.5. nh gi hiu qu ca PSS i vi n nh gc ti 71
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3.5.1. Trng hp khng s dng PSS v c s dng PSS 71
3.5.2. Trng hp s dng PSS1A v PSS2A 72
3.6. Kt lun chng 3 74
Chng 4. NG DNG IU KHIN TI U RH THIT K PSS
TI U CU TRC 75
4.1. Chuyn bi ton iu khin n nh tn hiu nh thnh bi ton iu
khin bn vng RH 75
4.2. Thit k b iu khin bn vng RH 80
4.2.1. Khi nim c bn v l thuyt iu khin ti u RH 80
4.2.2. Cc bc thc hin bi ton iu khin ti u RH 81
4.2.3. Thit k PSS ti u RH 85
4.3. M phng b iu khin 91
4.3.1. M phng trong Matlab 91
4.3.2. M phng theo thi gian thc 93
4.4. Kt lun chng 4 97
KT LUN V KIN NGH 99
DANH MC CC CNG TRNH C LIN QUAN N LUN N 100
TI LIU THAM KHO 101
PH LC 106
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DANH MC CC K HIU
x Cc vector bin trng thi
y Vector u ra ca h thng
u Vector u vo ca h thng
n n Ma trn c cc phn t 0 c kch thc n n
nI Ma trn n v c kch thc n
a, b, c Cun dy stator mi pha
fd Cun dy kch t
kd Cun cn theo trc d, (k=1,2)
kq Cun cn theo trc q, (k=1,2)
va, vb, vc in p pha tc thi stator
ia, ib, ic Dng in tc thi stator cc pha a, b, c
ifd, ikd, ikq Cc dng in mch kch t, cun cn dc trc v
ngang trc
rfd, rkd, rkq Cc in tr mch rotor, cun cn
laa, lbb, lcc T cm cc cun dy stator
lab, lbc, lca H cm gia cc cun dy stator
lafd, lakd, lakq H cm gia cc cun dy rotor v stator
lffd, lkkd, lkkq T cm ca mch rotor
Rs in tr pha phn ng (stator)
s Ton t laplace = d/dt
Gc rotor (gc ti) ca my pht (rad)
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Gc xc nh bi trc pha a v trc d (rad)
vs Gc pha u ca in p trn thanh ci h thng
Tc gc ca my pht (rad/s)
0 Tc ng b (rad/s)
Pm Cng sut c (p.u)
TM M men c (p.u)
Pe Cng sut in (p.u)
Te M men in (p.u)
Qe Cng sut phn khng (p.u)
TD M men dammping m men dp (damping torque)
TS M men ng b (synchronizing torque)
KD H s m men damping
KS H s m men ng b
H Hng s qun tnh my pht (s)
d T thng stator dc trc
q T thng stator ngang trc
Efd in p kch t
Vt in p u cc ca my pht (p.u)
Vd in p stator dc trc
Vq in p stator ngang trc
Id Dng in stator dc trc
Iq Dng in stator ngang trc
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Ed in p qu dc trc
Eq in p qu ngang trc
kd T thng mc vng cun cn dc trc
kq T thng mc vng cun cn ngang trc
Xd; Xd; Xd in khng ng b, qu v siu qu dc trc ca
my pht
Xq; Xq; Xq in khng ng b, qu v siu qu ngang trc
ca my pht
Xls in khng khe h (stator leakage inductance)
Td0; Td0 Hng s thi gian qu v siu qu d dc trc (s)
Tq0; Tq0 Hng s thi gian qu v siu qu d ngang trc (s)
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DANH MC CC CH VIT TT
Ch vit tt Biu din Ghi ch ting anh
PSS B n nh HT Power System Stabilizer
AVR T ng iu chnh in p Automatic Voltage
Regulator
LMI Bt ng thc ma trn tuyn tnh Linear Matrix Inequalities
LFO Dao ng tn s thp Low Frequency
Oscillation
LFC iu khin tn sti Loadfrequency Control
AGC Automatic Generation
Control
HTKT H thng kch t Excitation Systems
CSTD Cng sut tc dng Active Power
CSPK Cng sut phn khng Reactive Power
FACTS H thng truyn ti in xoay chiu
linh hot
Flexible AC Transmission
Systems
HVDC Truyn ti in mt chiu cao p High Voltage Direct
Current
SVC Thit b b cng sut phn khng
tnh
Static Var Compensator
HT H thng in Power System
MBA My bin p Transformer
AC Xoay chiu
DC Mt chiu
p.u n v tng i Per unit
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DANH MC CC HNH V, TH
Hnh 1.1. Cc phn t c bn ca mt HT 7
Hnh 1.2. Cc h thng iu khin con v iu khin lin quan ca mt trm pht
in 9
Hnh 1.3. Phn loi cc ch ca HT 10
Hnh 1.4. Cu trc iu khin HT 11
Hnh 1.5. S khi iu khin v bo v HTKT my pht in ng b 13
Hnh 1.6. iu khin tn s v phn phi CSTD trong HT 16
Hnh 1.7. c tnh cng sut ca my pht 17
Hnh 1.8. Phn loi n nh HT (nt m ch phm vi nghin cu ca lun n) 19
Hnh 1.9. Dao ng cc b 19
Hnh 1.10. Dao ng lin khu vc 20
Hnh 1.11. S khi iu khin HTKT c PSS 20
Hnh 1.12. Cu trc c bn ca PSS 21
Hnh 2.1. S khi mt my pht in ng b 29
Hnh 2.2. S my in ng b hai cc t 30
Hnh 2.3. S mch my kch t mt chiu c lp 36
Hnh 2.4. S mch my kch t t kch 37
Hnh 2.5. M hnh HTKT IEEE loi 1 [46] 39
Hnh 2.6. S khi ca h thng iu tc c kh - thy lc 41
Hnh 2.7. S khi ca h thng iu tc in t - thy lc 41
Hnh 2.8. M hnh h thng turbine v iu tc n gin 42
Hnh 2.9. S ng hc siu qu ca my pht [46] 45
Hnh 2.10. M hnh hai trc (two-axis) ca h my pht [46] 47
Hnh 2.11. M hnh ng hc flux-decay ca my pht in [46] 49
Hnh 3.1. S khi iu chnh kch t my pht ni li 52
Hnh 3.2. M hnh HTKT IEEE loi 1 vi tn hiu nh 56
Hnh 3.3. HTKT thyristor ST1A vi AVR 57
Hnh 3.4. S khi tuyn tnh ca my pht bao gm kch t & AVR 57
Hnh 3.5. p ng t nhin ca gc ti vi cc nhiu nh 59
Hnh 3.6. th vector cc thnh phn m men vi AVR 60
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Hnh 3.7. S khi tuyn tnh h my pht ni li vi kch t, AVR v PSS 60
Hnh 3.8. th vector cc thnh phn m men vi AVR & PSS 63
Hnh 3.9. S khi ca PSS1A loi u vo n 64
Hnh 3.10. S khi PSS2A (IEEE 421.5.1992) 66
Hnh 3.11. S khi ca PSS2B 66
Hnh 3.12. S khi ca PSS3B 67
Hnh 3.13. S khi ca PSS4B (Multi-band PSS) 67
Hnh 3.14. M hnh b chuyn i sai lch tc ca PSS4B 68
Hnh 3.15. Khu lc thng cao 69
Hnh 3.16. Khu lc thng cao v tch phn rt gn 69
Hnh 3.17. Cc cu hnh khu lc i vi cng sut c 69
Hnh 3.18. Khu khuch i v b pha 70
Hnh 3.19. p ng gc ti 71
Hnh 3.20. p ng tc rotor 71
Hnh 3.21. p ng sai lch tc 71
Hnh 3.22. p ng CSTD my pht Pe 71
Hnh 3.23. p ng gc ti 72
Hnh 3.24. p ng tc rotor 72
Hnh 3.25. p ng sai lch tc rotor 72
Hnh 3.26. p ng CSTD my pht Pe 72
Hnh 3.27. p ng gc ti 73
Hnh 3.28. p ng tc rotor 73
Hnh 3.29. p ng CSTD my pht Pe 73
Hnh 3.30. p ng sai lch tc rotor 73
Hnh 3.31. p ng gc ti 73
Hnh 3.32. p ng sai lch tc rotor 73
Hnh 4.1. S khi rt gn dng trong nghin cu 75
Hnh 4.2. Bi ton iu khin ti u RH 77
Hnh 4.3. th Bode ca b iu khin thit k (bc 28) 89
Hnh 4.4. th gi tr suy bin Hankel 89
Hnh 4.5. So snh th Bode ca b iu khin ban u v b iu khin gim bc
90
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Hnh 4.6. Gi tr suy bin a li ca m hnh R ban u 90
Hnh 4.7. So snh th Bode ca m hnh b iu khin ban u v b iu khin
sau khi gim bc (Rr_add v Rr_mult) 91
Hnh 4.8. p ng bc ca ba m hnh 91
Hnh 4.9. p ng sai lch gc ti 92
Hnh 4.10. p ng gc ti 92
Hnh 4.11. p ng sai lch tc 92
Hnh 4.12. p ng sai lch CSTD Pe 92
Hnh 4.13. p ng sai lch in p u cc Vt 92
Hnh 4.14. Hnh nh ca Card iu khin R&D DS1104 93
Hnh 4.15. Thit lp cho mi trng Solver chy thi gian thc 94
Hnh 4.16. Thit lp cho mi trng Realtime workshop chy thi gian thc 94
Hnh 4.17. Mi lin h gia cc phn mm iu khin 94
Hnh 4.18. S bn thit b m phng 95
Hnh 4.19. p ng sai lch gc ti 96
Hnh 4.20. p ng sai lch tc 96
Hnh 4.21. p ng sai lch CSTD Pe 96
Hnh 4.22. p ng sai lch in p u cc my pht Vt 96
Hnh 4.23. p ng sai lch gc ti c CPSS v PSSHinfi 97
Hnh 4.24. p ng sai lch gc ti c CPSS v khng c PSS 97
Hnh 4.25. p ng sai lch tc c CPSS v PSSHinfi 97
Hnh 4.26. p ng sai lch tc c CPSS v khng c PSS 97
Hnh PLI.1 S m phng trong Matlab (CPSS v khng PSS) 106
Hnh PLI.2 S m phng trong Matlab (PSS1A v PSS2A) 107
Hnh PLI.3 S khi ca CPSS (PSS1A) 108
Hnh PLI.4 S khi ca PSS2A 108
Hnh PLI.5 S m phng trong Matlab ca my pht in ng b ni li 109
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M U
K thut iu khin bn vng (robust) c ng dng cho thit k h iu
khin HT t cui nhng nm 1980. S tin li chnh ca k thut ny mang li l
mt cng c t nhin m phng thnh cng nhng trng thi khng n nh ca
nh my in. Mt s cc n lc gp phn vo vic thit k cho b n nh
HT (PSS) v/hoc cc thit b FACTS s dng khi nim H nh trong vic a
ra cng thc thit k nhy ho ln [34], [51], tng hp [16], [44] v khi nim
H2 trong LQG [23], [48]. Trong cc nghin cu ny rt nhiu cc mc ch iu
khin kinh in nh s suy gim nhiu lon, tnh n nh bn vng ca h thng c
nhiu c thc hin v gii quyt bng k thut tng hp H.
Gn y xut hin thm nhiu kt qu nghin cu c lin quan n vn ny.
in hnh l ca G. N. Taranto, J. H. Chow [49] a ra b iu khin cn bng m
hnh (modelmatching), cng trnh ca Hardiansyah, Seizo Furuya, Juichi Irisawa
[23] a ra b iu khin H, hay cng trnh ca J. H. Chow, J.J. SanchezGasca p
dng phng php gn im cc thit k PSS [17], Tuy nhin cc tc gi li
cha a ra thit k cc b iu khin p dng c rng trong cc iu kin vn
hnh, cng nh ch hn ch c s nh hng cc tn hiu ngoi sinh nh trng s
chn trc di iu kin chng phi l o c. R rng gi thit ny khng phi
lc no cng c tha mn trong thc t. Chnh v th cn thit phi nghin cu
pht trin cc h thng iu khin ny di gi thit tn hiu ngoi sinh l khng o
c hoc khng quan st c.
1. Tnh cp thit, ngha l lun v thc tin ca ti
Khi phi thit k, xy dng mt h thng iu khin bt k no , cc nh thit
k thng gp phi bi ton l b iu khin c thit k phi m bo cho h thng
c c cht lng lm vic mong mun nh n nh, tiu hao nng lng thp, tnh
bn vng cao,... trong di cng sut lm vic ln. C th thy ngay c rng yu cu
ny kh c th c p ng ch vi cc cng c iu khin c cu trc n gin
ang c s dng nhiu trong cng nghip nh b iu khin PI, PID,
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PSS l mt trong cc b iu khin hin ang c s dng trong cc nh my
in. Vit Nam, n c lp t trong cc nh my nhit in Ph Li, Ph M;
nh my thy in Thc B, Yaly v Sn La PSS c nhim v tng cng vic
gim cc dao ng tn s thp trong HT [42], [45] m rng gii hn truyn ti
cng sut v duy tr hot ng an ton ca mng li in. Tuy vy, n vn c mt
hn ch l mi b tham s iu khin ch m bo c tnh n nh cho h thng
trong mt di cng sut lm vic nht nh (nominal conditions), ngoi di cng
sut k s vn hnh bt buc phi t chnh nh li cc tham s lm vic ca
PSS. Hn th na, nhng tham s chun c gii thiu cng ch m bo c
tnh n nh khi h thng lm vic c lp v khng b cc tng tc khc ca
nhng h thng xung quanh tc ng di vai tr nh cc tn hiu nhiu ngoi sinh.
nng cao c kh nng lm vic bn vng cho cc b iu khin, hin
ngi ta vn s dng nguyn tc th cu l xy dng thm nhiu mch vng iu
khin b sung (cascade), bng cch s dng thm b iu khin PID cng nghip
[18], [50] v cc b lc leadlag [32]. Song ng tic, nh ti liu [22] ch r,
nguyn l iu khin bo th ny vn cha ng cc khim khuyt ca n v vn c
th dn ti s ph v ch tiu cht lng t ra ca h thng, chng hn nh vi s
gia tng ca cc ng dy truyn ti in di cng sut ln, cc my pht lp t
HTKT nhy cao th trong mt s trng hp, cc b iu khin trn khng m
bo c s tt dn i vi nhng dao ng trong h thng.
Gn y, l thuyt ti u RH [2], [41], [55] c pht trin m rng kho
cng c cho cc k s iu khin thit k iu khin bn vng, cho php to ra
c cc b biu khin b sung c kh nng m rng di cng sut lm vic nh
mc cho h thng m vn m bo c vic loi b cc tc ng ngoi sinh bn
ngoi. V vy, trong lun n ny xut xy dng cu trc b iu khin mi
trn c s l thuyt ti u RH nng cao cht lng iu khin n nh HT.
iu ny mang tnh cp thit v c ngha ln trong thc t.
2. Mc ch nghin cu ca ti
ng dng l thuyt iu khin ti u RH nng cao cht lng iu khin
n nh HT.
3. i tng v phm vi nghin cu
i tng nghin cu ca lun n l H thng in.
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Phm vi nghin cu ca lun n c gii hn trong vic nghin cu n
nh gc ti (gc rotor) vi cc nhiu nh, cc nhiu nh ny sinh ra bi thiu m
men damping hoc thay i v ph ti hay my pht trong qu trnh lm vic. K
thut thit k b iu khin y l l thuyt iu khin ti u RH.
4. Phng php nghin cu
Nghin cu l thuyt: Phn tch nh gi v h thng ha cc cng trnh
nghin cu c cng b thuc lnh vc lin quan: bi bo, tp ch, sch chuyn
ngnh; nghin cu cu trc v phng php la chn thng s PSS. nh gi u
nhc im cc b PSS .
Nghin cu thc tin: Nghin cu cu trc cc PSS ang lp t trong cc
nh my in hin nay Vit Nam, ri phn tch l gii so snh. Kim chng b
iu khin PSS thit k mi bng m phng trong Matlab R2010a & Simulink, sau
l m phng thi gian thc trn Card R&D DS1104. nh gi kh nng ng
dng ca b PSS mi.
Ly kin chuyn gia: Tham kho kin ca cc nh khoa hc Vin in
trng i hc Bch khoa H Ni, trung tm nghin cu trin khai cng ngh cao
trng i hc Bch Khoa H Ni; kin ca cc K s vn hnh nh my nhit
in Ph Li, thy in Sn La v nh sn xut thit b PSS ca hng ABB.
5. Nhng ng gp mi ca lun n
Lun n nghin cu mt cch h thng v PSS. ng dng l thuyt iu
khin ti u RH thit k PSS nng cao cht lng n nh HT. B iu khin
cho thy lm vic bn vng vi nhiu so vi cc PSS thng thng. Lun n
dng chun Hankel gim bc m hnh b iu khin, gip cho vic thc hin b
iu khin RH c tnh kh thi trong thc t.
Lun n nh gi c hiu qu ca cc loi PSS trong vn gim cc
dao ng gc rotor (dao ng c in tn s thp) ca my pht in. Kt qu ny
s gip cho cc k s vn hnh HT hiu r hn v thit k PSS theo l thuyt iu
khin ti u RH cng nh cch ci t PSS theo cc cu trc khc.
Kt qu nghin cu ca lun n m ra kh nng ng dng RH PSS trong
HT thc t.
6. Cu trc ca lun n
Ngoi phn m u, kt lun v kin ngh lun n gm cc chng sau y:
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Chng 1 gii thiu cu trc chung v HT; vn iu khin HT nh iu
khin in p, iu khin tn s HT; phn tch nguyn nhn gy nn dao ng gc
ti (gc rotor), tc hi ca dao ng v cch khc phc. Bin php khc phc y
l s dng PSS hot ng thng qua AVR dp tt cc dao ng c in ca my
pht in. Cui chng 1 trnh by cc vn nghin cu v PSS, bao gm cc
phng php thit k PSS nh m men damping, p ng tn s hay gi tr ring v
ma trn trng thi; cng nh phn tch cc tn ti v nghin cu cn b ng. c
bit trn nn l thuyt ti u RH tc gi xut phng php thit k b iu
khin PSS bn vng, c tnh ti u c v cu trc v tham s, thay th cho cc b
PSS hin c.
Chng 2 ca lun n c dnh xy dng m hnh ton tng qut ca
trm pht in trong HT. C th l xy dng m hnh ton ca my pht in trn
h ta dq0. Sau l xy dng m hnh ton ca cc khi iu khin lin quan
trong trm pht in nh h thng kch t, h thng turbine v iu tc. Phn tip
theo l xy dng m hnh ton ca h my pht in khi kt ni vi HT qua
ng dy ti in. Vi gi thit l HT lm vic ch xc lp nn tnh phi
tuyn ca mch t khng phi xt n, HTKT s dng l kch t IEEE loi 1. T
, ph hp vi phm vi v thc t nghin cu tc gi la chn m hnh ton
dng trong nghin cu l m hnh fluxdecay (m hnh bc 3).
Chng 3 tc gi i su phn tch b n nh HT PSS, t so snh nh
gi hiu qu cc b PSS hin c vi nhau. Phn u ca chng c dnh xy
dng m hnh ton tuyn tnh ha xung quanh im lm vic ca h my pht
kt ni vi HT khi b nhiu lon nh tc ng, t a ra c h phng trnh
trng thi ca HT. Da trn h phng trnh trng thi v s khi xy dng
c, tc gi gii thch bn cht vt l cc thnh phn m men khi cha c AVR
v khi c AVR. Kt qu phn tch cho thy nhc im ca vic s dng AVR
nhy cao do to ra thnh phn m men damping tng theo chiu m, khin hot
ng ca my pht khng n nh. Bng vic b sung thm mt thnh phn vector
m men cng pha vi sai lch tc s khc phc c nhc im ca AVR,
thnh phn m men ny chnh l do PSS to nn. Phn tip theo ca chng 3 gii
thiu cc cu trc ca PSS theo chun IEEE 421.5.2005, phn tch cc thnh phn
trong cu trc ca PSS2A/2B. Cui chng 3 thc hin nh gi hiu qu ca PSS
i vi n nh gc ti trong hai trng hp: i) h thng khng s dng PSS v c
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s dng CPSS; ii) h thng s dng PSS1A v PSS2A. Kt qu m phng trong
Matlab v thi gian thc cho thy hiu qu kh tt ca vic s dng PSS i vi n
nh gc ti, dn n n nh tc rotor v CSTD u ra my pht. Tuy nhin,
cht lng n nh cha cao. Do , tc gi mi xut thit k b iu khin PSS
bn vng theo l thuyt ti u RH. Pht hin ny v nhng kt qu nghin cu
trong chng 3 l mt ng gp ca lun n.
Chng 4 l chng trng tm ca lun n. Cng vic u tin c dnh cho
vic chuyn bi ton iu khin n nh tn hiu nh thnh bi ton iu khin bn
vng. T , thy c nhim v cn phi thc hin khi thit k b iu khin PSS.
Phn tip theo trnh by tng quan v l thuyt iu khin ti u v cc bc thit
k b iu khin bn vng PSS: bc mt, xc nh tp tt c cc b iu khin
(s) lm h kn n nh; bc hai, tm mt phn t R(s) trong tp (s) sao cho vi
n c c nhy cm vi sai lch m hnh S v vi nhiu p cng nh quan h
Gpz(s) l nh nht. Vi cng c h tr l phn mm Matlab, tc gi tm ra
b iu khin bc 28. b iu khin c tnh kh thi trong thc t, tc gi dng
chun Hankel gim bc. Kt qu thu c l b iu khin bc 6. Phn cui ca
chng 4 dnh cho vic m phng b iu khin trong hai trng hp. M phng
trong Matlab v m phng theo thi gian thc. Tc gi dnh mt thi lng ng
k cho vic kim chng b iu khin bng m phng thi gian thc ti trung tm
nghin cu trin khai cng ngh cao trng i hc Bch Khoa H Ni. Cc kt
qu m phng cho thy b iu khin bn vng PSS c tc dng r rt i vi vic
rt ngn thi gian dao ng gc ti v h thp c bin dao ng gc ti so vi
cc b PSS truyn thng. Kt qu nghin cu trong chng ny l mt ng gp
mi v quan trng ca lun n.
Phn cui cng ca lun n l cc cng trnh cng b lin quan n lun n,
cc ti liu tham kho v phn ph lc.
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1 Chng 1. TNG QUAN
Equation Section 1
1.1. Gii thiu cu trc h thng in
Hnh 1.1 minh ha cc phn t c bn ca mt HT hin i. in nng c
to ra trm pht in (GS) v c truyn ti n h tiu th thng qua mng li
in phc tp bao gm cc ng dy truyn ti, cc MBA, cc thit b ng
ctTa c th phn mng li in thnh cc h thng nh sau:
H thng truyn ti
H thng truyn ti trung gian
H thng phn phi
H thng truyn ti lin kt tt c cc trm pht in chnh vi cc trung tm
ph ti trong h thng. N to ra xng sng ca HT hp nht v hot ng cc
cp in p cao nht (in hnh l 220kV v cao hn). V in p u ra ca my pht
thng trong khong t 10,5 n 35kV, nn nhng in p ny s c nng ln cao
bi MBA trc khi truyn ti i xa n cc trm truyn ti trung gian, ti y in p
c h xung cp in p truyn ti trung gian (thng l 69kV n 138kV).
H thng truyn ti trung gian truyn nng lng in vi cng sut nh hn
t cc trm truyn ti n cc trm phn phi. Cc h tiu th in ln cng nghip
c cung cp in trc tip t h thng truyn ti. mt s h thng, khng c
ranh gii r rng gia mng in truyn ti v mng truyn ti trung gian.
H thng phn phi tng trng cho giai on cui trong vic truyn ti in
nng ti cc h tiu th ring l. in p phn phi s cp thng nm trong
khong 6kV n 35kV. Cc h tiu th in cng nghip nh c cung cp in
trc tip t cc ng dy cp in p ny. Cc h tiu th in sinh hot v
thng mi th tiu th pha th cp MBA vi in p 380/220V.
Cc trm pht in nh t gn ph ti thng c kt ni trc tip ti h
thng truyn ti ph hoc h thng phn phi. Cn s lin kt gia cc HT gn
nhau thng c thc hin cp h thng truyn ti.
HT nh m t trn y to nn s phc tp v cu trc cng nh tin
cy,... Mt mt, HT ny cho php khai thc ti a cc u im vn hnh kinh t
(phi hp vi cc ngun thu nhit in, ti u ho cng sut ngun); cho php
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h thng chng li c cc s c bt thng m khng lm gin on vic cung
cp in cho cc h tiu th. Mt khc, l tin thun li cho vic pht trin cc
ngun in cng sut ln v vic u ni vo h thng. Tuy nhin, cng lm ny
sinh vn v n nh HT [5], [30].
GS
GS
Ph ti
cng nghip
Trm pht in nh
Ph ti cng nghip
Ph ti thng mi Ph ti sinh hot
500kV 500kV 220kV 22kV 15,75kV
500kV
500kV 220kV
ng dy trung p
380/220V
110kV
Trm phn phi
110kV
6/10/22kV
Trm truyn ti
Kt ni vi HT bn cnh
H th
ng t
ruyn t
i
500kV
H th
ng t
ruyn t
i
220kV
220kV
0,4kV
22kV
Hnh 1.1. Cc phn t c bn ca mt HT
T
i
n
g d
y tru
yn t
i
trung g
in
ng d
y
truyn t
i tr
ung
gi
n K
t
ni v
i
ng
dy b
n c
nh
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1.2. iu khin h thng in
1.2.1. Nhim v iu khin HT
Chc nng ca mt HT l bin i nng lng t mt dng t nhin sang
dng in v truyn ti n cc im tiu th. S tin li ca nng lng in l d
truyn ti v iu khin vi hiu sut v tin cy cao. Trong qu trnh vn hnh
HT cn m bo cc yu cu sau y:
1. H thng phi c kh nng p ng mt cch lin tc vi s thay i nhu cu ti
CSTD v CSPK. Khng ging nh cc dng nng lng khc, in nng khng
th tch tr vi dung lng ln c. Bi vy, rt nhiu thit b v b iu khin
c s dng duy tr cn bng cng sut tiu th v cng sut pht.
2. Cht lng in nng phi m bo cc tiu chun sau y:
Tn s h thng khng i
in p nt khng i
Hnh 1.2 m t mt s khi iu khin ca mt trm pht in trong HT.
Trong mi khi iu khin my pht c cha khi iu tc v khi iu khin kch
t. Khi iu tc c nhim v iu chnh tc v iu khin mt s bin cung cp
nng lng nh p sut hi, nhit v lung nng lng. Chc nng ca khi iu
khin kch t l iu chnh in p v CSPK u ra my pht.
Mc ch ca h thng iu khin my pht l cn bng cng sut pht vi
cng sut ti cng cc tn tht. Bi vy, tn s v CSTD c quan h mt thit
vi nhau.
H thng iu khin ng dy truyn ti bao gm cc thit b iu khin
cng sut v in p, nh thit b b tnh SVC, my b ng b, t in,
khng in ng ct, b iu p MBA, MBA dch pha v cc thit b iu
khin ng dy HVDC. Mc ch l duy tr in p, tn s cng nh cc
thng s khc ca h thng nm trong gii hn cho php.
Cc h thng iu khin m t trn y gp phn tho mn s lm vic ca
HT. Chng c nh hng ng k n c tnh ng hc ca h thng v kh
nng i ph vi cc nhiu lon.
Cc mc ch iu khin c da trn ch lm vic ca HT. Trong cc
iu kin bnh thng, mc ch iu khin l m bo in p v tn s gn vi
gi tr nh mc. Khi pht sinh iu kin khc thng, mc ch iu khin l a
h thng v ch bnh thng.
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Da vo [30], [31], c th phn loi ch ca HT ra cc loi sau y: bnh
thng, cnh bo, nguy him, s c v phc hi sau s c. Hnh 1.3 m t cc ch
ny v phng thc tc ng gia chng.
Trong ch bnh thng, tt c cc thng s ch h thng nm trong
phm vi nh mc v khng c thit b no b qu ti. H thng lm vic an ton v
c kh nng tr vng vi nhng bin c ngu nhin m khng vi phm bt c rng
buc no.
iu -K hoch sn xut
H thng kch t v iu khin
My pht
Khi iu khin my pht
Dng in kch t K
hi
iu k
hi
n m
y
pht
kh
c
v
c
c
iu k
hi
n li
n q
ua
n
Cng sut trc
iu khin ng dy ti in
Tn s Trao i cng sut
Cng sut my pht
Tc /cng sut
in p
H thng iu khin my pht
Tn s Trao i cng sut
Cng sut my pht
Tc
Hnh 1.2. Cc h thng iu khin con v iu khin lin quan
ca mt trm pht in
iu tc v iu khin
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Nu mc an ton di
gii hn chc chn, hoc khi h
thng chu mt nhiu lon gia tng
do iu kin thi tit (bo), th h
thng ri vo ch cnh bo.
ch ny, tt c cc bin ca h
thng vn cn nm trong gii hn
cho php v cc rng buc vn cn
c tha mn.
Khi h thng ch cnh
bo, nu xy ra nhiu ln th h
thng ri vo ch nguy him. ch ny, in p nhiu thanh ci gim thp
v/hoc thit b b qu ti. H thng vn c th duy tr v c th quay tr v ch
cnh bo bng cc bin php iu khin khn cp nh: loi tr s c, iu khin
kch t, ng m van nhanh,
Nu cc bin php trn khng c s dng hoc khng c hiu qu, th h
thng s b s c, hu qu l lm s c lan rng v c th sp h thng. Cc hot
ng iu khin nh xa thi ph ti v iu khin h thng b phn tch hon ton.
Ch phc hi sau s c c th hin bng hot ng iu khin ti kt ni
li tt c cc iu kin thun li v khi phc li ti h thng. H thng c chuyn
t ch ny sang ch cnh bo, ch bnh thng c hay khng l cn ty
thuc vo iu kin lm vic thc t ca h thng.
Cc ch h thng phn loi nh trn cung cp khun kh cho cc chin
lc iu khin gip cho cng tc vn hnh HT c hiu qu.
1.2.2. Cu trc iu khin HT
Hnh 1.4 l s cu trc iu khin HT, phn chia lm hai khi: cc b
iu khin lp t pha nh my in v cc b iu khin lp t pha ng dy
truyn ti in:
Khi iu khin pha nh my c hai b phn c bn: mt l iu khin tn s
ti (LFC) hay iu tc turbine, dng gi tn s ca my pht gi tr nh
mc (50Hz), mt b phn quan trng khc l h thng iu khin kch t. B
phn LFC khng nhanh ci thin n nh ca h thng, v hng s thi
S c Nguy him
Cnh bo Phc hi
Bnh thng
Hnh 1.3. Phn loi cc ch ca HT
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gian ca n ln; cn iu khin kch t c th hot ng rt nhanh v hng s
thi gian ca n rt nh.
Trong khi HTKT dng ci thin n nh cho my pht ng b, th cc thit
b FACTS [9] dng n nh cc dao ng trn cc ng dy truyn ti
in. FACTS c nh ngha l vic s dng k thut in t cng sut ln
in p cao, vi cc b vi x l, cc thit b vi in t iu khin HT.
FACTS c thit k vt qua cc gii hn v mt c kh ca ng dy
truyn ti in xoay chiu. FACTS gp phn gia tng kh nng truyn ti,
kh nng iu khin cng sut v dp tt cc dao ng trong HT [9], [40].
Ngoi cc khi iu khin nu trn, trong HT Vit Nam cn c trung tm
iu HT quc gia (A0), di l cc iu min Bc, min Nam v min
Trung ch huy vn hnh HT p ng yu cu sn xut v tiu th in nng.
Sau y ta s phn tch phng php iu khin hai thng s quan trng ca
ch h thng in l in p v tn s.
1.2.2.1. iu khin in p
a) Gii thiu chung
iu khin in p ngi ta thc hin iu khin vic sn xut, tiu th
CSPK tt c cc cp trong HT. Cc my pht l phng tin c bn iu
khin in p, trong vic iu khin dng in kch t thng qua AVR s duy tr
c in p u cc cc my pht in. Cc phng tin thm vo iu khin
in p c th phn loi nh sau:
Ngun CSPK, nh t b ngang, khng b ngang, my b ng b v SVC
B khng ng dy, nh t b dc
MBA iu chnh, nh MBA c iu chnh in p di ti v MBA tng p
Pha nh my in
Hnh 1.4. Cu trc iu khin HT
Cc b iu iu khin HT
Pha tryn ti in
Turbine iu khin tn s ti (LFC)
(chm)
Kch t, AVR (nhanh)
FACTS (nhanh)
B iu khin c kh (chm)
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HTKT (bao gm kch t v AVR) l mt trong cc h thng thit b quan
trng nht quyt nh n s lm vic an ton ca my pht in. N c nhim v
cung cp dng in mt chiu cho cun dy kch t ca my pht in ng b.
Khi my pht cha ni vo li in, vic thay i dng in kch t ch thay
i in p u cc my pht. Tuy nhin khi my pht in c ni vo li in c
cng sut rt ln so vi my pht, vic tng gim dng kch t hu nh khng lm
thay i in p li. Tc dng ca HTKT khi l iu khin CSPK ca my pht.
t ng iu chnh dng kch t ca my pht in ng b, ngi ta s
dng h thng t ng iu chnh kch t c b phn iu khin chnh l thit b t
ng iu chnh in p AVR. Thit b ny c nhim v gi cho in p u cc
my pht l khng i (vi chnh xc no ) khi ph ti thay i v nng cao
gii hn truyn ti cng sut ca my pht vo HT, c bit khi my pht c
ni vi h thng qua ng dy di. Nhng yu cu chung vi h thng t ng
iu chnh kch t l: m bo n nh tnh (vi nhiu nh) v nng cao tnh n nh
ng (vi nhiu ln); cn c ch kch thch cng bc khi my lm vic ch
s c (nh ngn mch trong li)
Hiu qu thc hin cc nhim v nu trn ph thuc vo c trng v thng s
ca HTKT [13], [27].
b) Phn loi kch t
Kch t c th chia ra cc loi sau y [13], [27]:
Kch t mt chiu loi DC
Kch t xoay chiu loi AC
Kch t tnh loi ST
c) Chc nng iu khin v bo v ca HTKT
Mt HTKT hin i c nhiu chc nng hn b iu chnh in p thng
thng. Bao gm iu khin, gii hn v bo v m c cp trong cc yu
cu ca HTKT. S khi giao tip cc b phn chc nng ny c trnh by
hnh 1.5. Mt HTKT c th ch bao gm mt vi hoc tt c nhng chc nng ny,
tu thuc vo yu cu ca tng ng dng c th v loi my kch t.
V l thuyt, mi chc nng iu khin iu chnh mt i lng ty theo yu
cu c th, chc nng gii hn m bo chc chn cc i lng khng vt qu tr
s t. Nu bt c b gii hn no b s c, chc nng bo v s loi b chnh xc
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phn t hoc cc b phn c lin quan ra khi h thng. Sau y ta s lm r cc
chc nng iu khin v bo v y.
B iu chnh AC v DC
Chc nng c bn ca b iu chnh AC l duy tr in p stator my pht.
Ngoi ra cn c chc nng bo v v iu khin ph khc iu khin in p
kch t my pht.
Chc nng b iu chnh DC l gi cho in p kch t my pht khng i v
thng thc hin bng tay. Trong mt vi HTKT, im t c hiu chnh t
ng, v vy lm cc tiu lch in p.
B b ti (b to c tuyn)
Bnh thng, chc nng ca AVR l iu khin in p u cc my pht.
Trng hp ny, c tnh iu chnh in p my pht l ng khng ph thuc
vo ti my pht v c gi l c tnh c lp. i khi, b b ti c s dng
iu khin in p ti mt im bn trong hoc bn ngoi my pht. thc hin
B iu chnh AC
My kch t
Gii hn qu kch t
Gii hn thiu kch t
B gii hn v bo v
V/Hz
Mch dit t
My pht
B iu chnh DC
Cm bin in p
T
i H
T
in p t AC
in p t DC
AVR
Hnh 1.5. S khi iu khin v bo v HTKT my pht in ng b
Cm bin in p v b b ti (to c tuyn)
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iu ny ngi ta s dng thm mt mch u vo AVR nh hnh 3.15. Trng
hp ny, c tnh iu chnh in p l ng thng dc ln hoc dc xung, gi l
c tnh ph thuc dng hoc m [6], [30]. B b c iu chnh nh in tr RC
v in cm khng XC. S dng tr khng ny v dng in phn ng s thay i
c in p ging thm vo hoc bt i in p u cc my pht. Gi tr in
p b a n AVR c tnh nh sau: ( )C t c c tV V R jX I , r rng vi gi tr
dng ca RC v XC in p ging s c thm vo in p u cc my pht,
B gii hn thiu kch t (UEL-under excitation limiters)
B gii hn thiu kch t dng ngn chn s gim kch t ca my pht ti
mc m gii hn n nh tn hiu nh hoc gii hn nhit li stator b vt qu.
Tn hiu iu khin ca b gii hn thiu kch t c ly t s kt hp hoc
l in p v dng in, hoc l CSTD v CSPK ca my pht. C nhiu cch b
sung chc nng thc hin ca b gii hn thiu kch t. Mt s hot ng theo tn
hiu sai lch in p ca b AVR, khi b gii hn khi ng, mt phn t khng
tuyn tnh (diod) bt u cho ra tn hiu, v kt hp vi cc tn hiu iu khin khc
ca HTKT.
S ci t c tnh ca b gii hn thiu kch t s t nn tng cho bo v
nh bo v h thng mt n nh hoc l cun dy stator pht nng. Ngoi ra c
tnh ca b gii hn cn c phi hp vi b bo v mt kch t my pht. c
tnh ca b gii hn cn thng s dng kt hp vi tnh ton n nh tn hiu nh
v c tnh rle chng mt kch t.
B gii hn qu kch t (OEL- over excitation limiters)
Mc ch ca b gii hn qu kch t l bo v my pht khng b qu nhit do
qu dng kch t.
Hin nay, vic b sung chc nng gii hn qu kch t thay i tu thuc vo
hng sn xut v chc nng c th. Chc nng c trng ca b gii hn qu kch t
l pht hin ra dng kch t cao, sau thi gian tr n tc ng thng qua b iu
chnh AC nhm lm gim dc kch t n gi tr t trc (khong 100 110%
dng kch t nh mc). Nu khng c n s ct b iu chnh AC, chuyn iu
khin n b iu chnh DC v xc nh li im t mt gi tr p ng tng
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ng vi tr s nh mc. Nu iu ny cng khng lm gim kch t n mt gi tr
an ton th b gii hn s tc ng ct my ct kch t v ct my pht.
B gii hn V/Hz v bo v
Nhng mch ny c s dng bo v my pht v MBA tng p khng b
h hi do vt qu dng t ho l kt qu ca tn s thp v qu in p. Dng t
ho vt qu lin tc l nguyn nhn dn n s qu nhit. Hu qu, c th lm h
hi MBA v cun dy my pht. T s ca in p tng i v tn s tng i
c xem nh volts chia cho hertz (V/Hz) c th o lng c bng i lng t
l vi dng t ho. Gi tr V/Hz thng nm trong khong (1,05-1,25) [30].
Mch dit t
Bnh thng, b chnh lu khng dn theo chiu ngc li, nn dng in ca
b kch t khng th m nh trng hp ca kch t AC v kch t tnh. Trong
trng hp u cc my pht b h hng v h thng b ngn mch, dng cm ng
trong cun kch t c th m. Nu dng in ny khng c ng thot th in p
tng rt cao c th to ra mch t mc song song. V vy, mt mch in ring
bit c cung cp lm nhnh r cho php dng kch t m thot qua. y l mt
hnh thc ni tt t trng, nn thng c bit n qua b dp t trng hoc
in tr bin i [30].
1.2.2.2. iu khin tn s
Qu trnh iu khin tn s gn lin vi iu khin tc ca my pht in
ng b. Tn s ca h thng c m bo da trn s cn bng CSTD. Trong h
thng c nhiu t my, nhiu nh my in nn cn c s phn phi cng sut gia
cc t my vi nhau. B iu chnh tc turbine (governor) ca mi my pht lm
chc nng iu chnh tc s cp, trong khi b iu khin th cp lm nhim v
phn phi cng sut (AGC) [6], [30].
Tn s l mt trong nhng tiu chun nh gi cht lng in nng. lch
tn s khc vi lch in p ch l tt c cc im ang lm vic ng b ca
h thng l ging nhau. S thay i tn s xy ra do s mt cn bng cng sut tng
ca turbine v ph ti ca my pht, iu ny c m t bi phng trnh (1.2).
R rng khi tng hoc gim ph ti hay khi s c t my s xut hin mt cn
bng cng sut dn n thay i tn s trong h thng. Tn s c iu chnh bng
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cch thay i lng hi nc (nc) a vo turbine my pht. Nh vy vic iu
chnh tn s trong HT lin quan mt thit vi iu chnh CSTD gia cc t my
v nh my in.
Trong h thng lin kt c hai hay nhiu khu vc iu khin c lp nhau, ngoi
b iu khin tn s ngun pht trong mi khu vc cn phi iu khin duy tr
lng cng sut gia cc khu vc theo k hoch nh trc. iu khin ngun pht
v tn s thng thng c bit n vi thit b iu khin tn sti (LFC).
S iu khin tn s v phn phi CSTD t ng trong HT c m t
nh hnh 1.6. Ngy nay, cc thit b t ng iu khin cho php duy tr tn s h
thng kt hp phn b kinh t cng sut gia cc t my ni song song, ng thi
iu khin dng cng sut cn thiu ht gia HT v nh my.
1.3. Vn dao ng gc ti trong HT
1.3.1. nh ngha gc ti (gc rotor)
c tnh quan trng ca HT l mi quan h gia cng sut v v tr gc ca
rotor. minh ha iu ny chng ta hy xt mt HT n gin cho trn hnh 1.7a.
Bao gm my pht ng b kt ni vi HT qua ng dy ti in c in khng
l Xe.
Gc ti (gc rotor) l gc gia vector sc in ng bn trong gE do t
thng dng in kch t sinh ra vi vector in p trn thanh ci u cc
t tV V .
Thay i tc
HT iu khin turbine s cp
Van hay cng cnh hng My pht
B iu khin th cp (AGC)
Ti, HT truyn ti, cc t my khc
Nng lng s cp
Cng sut truyn ti trn ng dy
Hnh 1.6. iu khin tn s v phn phi CSTD trong HT
Turbine
Tc
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Hnh 1.7b l s thay th l tng ( b qua in tr v in dn cc phn
t) xc nh mi quan h gia cng sut vi gc. Hnh 1.7c biu din th
vector pha gia my pht v h thng. ch xc lp cng sut u ra ca my
pht cho bi [30], [39]
sing t
eg
EVP
X (1.1)
p ng ca mi quan h cng sut v gc c biu din nh hnh 1.7d.
Vi cc m hnh c l tng ho s dng biu din my pht ng b (nh
gi thit), th s thay i cng sut theo gc c dng hnh sin. Cn vi cc m
hnh my pht i hi s chnh xc cao nh xt n nh hng ca qu trnh in
t, th mi quan h cng sut gc c th lch khi dng sin, tuy nhin dng chung l
ging nhau. Khi gc bng khng, cng sut bng khng. Nu gc tng, cng sut
truyn ti s tng ti gi tr cc i thng c m bo bng 900, sau nu gc
tip tc tng cng sut s gim. Cn tip tc tng gc na s dn ti mt n nh.
Vt
Eg
IXe
c) S vector
VS
IXg
P
Pmax
d) c tnh cng sut - gc
G
Xe ng dy Xg
HT
gE a) S HT
b) S thay th l tng
I
t tV V
0S SV V
900
Hnh 1.7. c tnh cng sut ca my pht
1800 0
Pm
I
a
im lm vic
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1.3.2. Cn bng cng sut trong HT
Trong qu trnh vn hnh, khi b nhiu lon bi s thay i t ngt, tc v
cng sut ca my pht s bin i xung quanh im vn hnh. Mi quan h ny c th
c biu din bi phng trnh chuyn ng sau y (trong h n v tng i) [30]:
2
2
0
2M e
H dT T
dt
(1.2)
trong :
gc rotor (rad)
0 tc gc ca rotor, gi tr c s hoc gi tr nh mc bng 02 f rad/s
TM m men c (p.u)
Te m men in (p.u)
H hng s qun tnh ca my pht (MWs/MVA)
Theo (1.2), ch xc lp ca HT, c s cn bng gia m men c u
vo v m men in u ra ca mi my pht ( )M eT T v gc ti, tc rotor duy
tr l hng s. Nu h thng b xo trn, im cn bng s b thay i, kt qu lm
cho rotor b tng tc hay gim tc so vi tn s h thng, khin hot ng ca my
pht c th khng n nh.
1.3.3. Nguyn nhn gy ra dao ng gc ti
Khi c ti yu cu n mt trm c nhiu t my, b phn phn phi cng sut
(AGC) s lm nhim v phn cng sut cho cc t my hng ti s cn bng.
Tuy nhin do ng hc ca mi my pht l khc nhau, gy nn cc lung cng sut
trao i trong ni b trm pht, hoc gia my pht vi h thng qua ng truyn.
Nhng tc ng xen knh ny khin cho rotor my pht dao ng xung quanh im
lm vic.
Mt ngun khc gy nn dao ng gc ti l vic s dng cc b kch t p
ng nhanh vi AVR h s khuch i ln c tc dng ci thin gii hn n nh tnh
v n nh ng, nhng li lm gim thnh phn m men damping, gy bt li vi
n nh tn hiu nh [11].
Tc hi ca dao ng:
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Khi gc ti dao ng khin tc rotor khng cn l tc ng b na, gc
ti c th vt qu 900 in
(hnh 1.7d), lm cho hot
ng my pht b mt ng
b, trong trng hp khng
c khng ch kp thi,
n rt c th b cng hng
vi nhng dao ng khc
gy nn mt ng b
nghim trng gia cc my
pht v li in thm ch
gy tan r HT.
Cch tip cn nghin cu n nh:
Trong cch phn loi n nh HT nh hnh 1.8 [30], [31], th n nh gc ti
chia ra lm hai loi v y ta ch xem xt bi ton n nh tn hiu nh (nhiu lon
nh). Cc nhiu lon ny c coi l nh cho php ta c th s dng phng
trnh tuyn tnh ca h thng phn tch n nh.
L thuyt n nh tn hiu
nh c dng nhn dng v
phn tch cc dao ng c in
(dao ng tn s thp) trong
HT. Cc dao ng ny lm
cho gc rotor ca my pht tng
ln hoc gim i so vi im
lm vic v l nguyn nhn ca s thiu m men ng b hoc m men damping
[7]. Dao ng tn s thp gm c cc dng sau y [42], [45]:
Cc dao ng cc b: Nhng dao ng ny thng lin quan n mt hoc nhiu
my pht ng b quay vi nhau ti mt nh my in so vi mt HT ln hay
trung tm ph ti. Tn s dao ng trong khong 0,72Hz. Nhng dao ng ny
gy phin toi khi nh my ti cao vi h thng ng truyn c in khng ln.
Cc dao ng lin khu vc: Nhng dao ng ny thng lin quan n vic kt
hp rt nhiu my pht ti mt phn ca HT i vi phn khc ca HT thng
qua ng truyn yu. Tn s cc dao ng lin khu vc thng nh hn 0,5 Hz.
n nh H thng in
n nh gc ti n nh in p
n nh qu (nhiu ln)
Hnh 1.8. Phn loi n nh HT (nt m ch
phm vi nghin cu ca lun n)
n nh tn s
n nh tn hiu
nh (nhiu nh)
Eg
Xe Xg
0,7-2Hz
Hnh 1.9. Dao ng cc b
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Cc dao ng ton cu: Nhng dao ng ny lin quan n nhiu HT ln kt
ni vi nhau trn din rng. Tn s dao ng nh hn 0,2Hz.
Vic iu khin dp dao ng c thc hin thng qua HTKT. Trong my
pht in ng b ngi ta cng b tr cc vng dy ngn mch trn rotor (cun
cn), tiu tn nng lng dao ng v lm cho cc dao ng ca my pht tt
nhanh hn. Tuy nhin vic lm ny khng th trit tiu ht cc dao ng. Gii php
B iu chnh AC
My kch t
Gii hn qu kch t
Gii hn thiu kch t
B gii hn v bo v
V/Hz
Mch dit t
My pht
B iu chnh DC
Cm bin in p
PSS
T
i H
T
in p t AC
in p t DC
AVR
Hnh 1.11. S khi iu khin HTKT c PSS
Cm bin in p v b b ti (to c tuyn)
Eg1
Xe Xg1 Xg2
Eg2
0,5Hz
Hnh 1.10. Dao ng lin khu vc
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cho vn ny l s dng thit b n nh HT PSS hot ng thng qua cc b
iu chnh in p AVR, c s ni vo h thng iu khin nh hnh 1.11.
1.4. B n nh HT - PSS
Nhim v ca PSS l c lng dao ng ( )t gi tn hiu in p PSSV tc
ng ln mch kch t to ra mt thnh phn m men in t dp dao ng .
Thay v phi o trc tip gc ti, ngi ta thng o bin thin tc rotor ( )t
v/hoc cng sut in my pht ( )eP t ng tr vi ( )t ri ly hai tn hiu
lm u vo cho PSS.
ci thin s tt dn cc dao ng, PSS phi to ra thnh phn m men in
cng pha vi sai lch tc rotor . Hn na, PSS phi c mch b pha thch
hp b vo s tr pha gia u vo kch t v u ra m men in t.
Theo chun IEEE 421.52005 [27], PSS chia ra: PSS1A y l loi c mt
u vo nh sai lch tc , sai lch tn s f , cng sut in eP ; PSS u
vo kp, thng l sai lch tc v cng sut in eP (PSS2A, PSS2B,
PSS3B v PSS4B).
Hnh 1.12 l s khi c bn ca mt PSS s dng trong HT. N bao gm
khu lc washout, khu b lead-lag, khu lc xon v khu gii hn. Cu trc c
bn ca mt loi PSS da trn tn hiu tc thng gm c:
o tc u trc bng cch dng mt cc t v cch b tr bnh rng.
Chuyn i tc o c sang dng in p mt chiu t l vi tc .
Khu lc thng cao loi b mc tc trung bnh, iu ny m bo rng
PSS ch phn ng vi nhng thay i trong tc m khng thay i in p
t u cc my pht.
p dng vt pha to ra tn hiu b chm pha trong mch vng iu khin
in p.
iu chnh h s khuch i ca tn hiu cui cng a n u vo AVR.
w
w1
sT
sT
Khu lc
( )FILT s
Khu lc xon Khu gii hn
Hnh 1.12. Cu trc c bn ca PSS
( )T s
Khu b lead-lag eB
ook f
or Yo
u
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Cu trc ca PSS kp vi hai u phn hi [8], [27], [32] s c phn tch chi
tit chng 3. Tu chung ca tt c cc PSS hin ang s dng l c cu trc
cng vi nhng tham s c chn t do v thng khng nht qun. Mi hng sn
xut c mt lun im ring kh phc tp v vic chn nhng tham s ny.
1.5. Nhng vn nghin cu v PSS
1.5.1. Mt s phng php thit k PSS
Trong thc t cc my pht in tc ng vi nhau thng qua in p v dng
in, nh hng ng hc ca cc my l khc nhau. Do phi xem xt mt cch
c th khi thit k PSS, iu ny c bit n ging nh vic phi hp iu chnh
ca PSS trong h thng c nhiu my pht. Mt cch tng qut chng u tp trung
vo cc phng php nh: m men damping, p ng tn s hay gi tr ring v ma
trn trng thi. Sau y l mt s k thut s dng kt hp cc phng php tip
cn ny [12].
1.5.1.1. Phng php tip cn m men damping
Khi s dng phng php ny chng ta phi tm cc h s 1 6K K ca m
hnh Heffron Phillips [25], cng nh s nh hng ca cc my pht khc tc
ng ln mt my c th, vic tnh ton bng cch b sung thm m men lm gim
s dao ng c gi l m men damping. Trong di tn s rng, l thuyt phn
tch tn hiu nh c s dng kim tra dao ng tt dn ca mi my pht.
thc hin c, trc tin chng ta phi tm hm truyn /vi ei ssiH s T s V s
gia in p u vo v m men in u ra ca tng my pht. nh hng ca
thay i tc ti m men in c m hnh ha thng qua hai hm truyn: mt
l thng qua gc ti ging nh nh hng ca s thay i in p thng qua mng
/i ei iH s T s s ; hai l thng qua tc u vo PSS, biu din
bi /i ei iH s T s s .
Vi ba hm truyn trn, bin gc quay v tc ca viH s phi c gi
khng i, iu ny c th thc hin bng cch to ra hng s qun tnh ca my
pht ln. Trong vic lp ma trng thi, cn quan tm n sai lch tc i
ca tt
c cc my pht ging nh u vo, bng cch b i mt hng ca ma trn trng
thi A tng ng vi phng trnh vi phn tuyn tnh di chuyn i ct tng ng
vi bin trng thi tc vector u vo. Khi chng ta c th kim tra nh
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hng ca m men in eiT s ca my pht th i, coi nh nhiu trong tc ca
cc my pht khc j
. iu cng mang li kh nhiu thng tin ca s tc ng
ln nhau gia hai my pht nhng di tn s khc nhau. Khi khng c PSS, hm
truyn iH s thng qua gc quay ca rotor cung cp mt m men lm gim s dao
ng, nhng gi tr m men ny rt nh nn khng th dp tt dao ng c.
i vi nhng my pht quan trng yu cu phi c PSS, hm truyn
iH s mang thng tin ca PSS khi kt ni n trong h thng s cung cp m men
ngc vi m men dao ng, thng qua gc rotor trong hm truyn iH s . Phn
thc dng ca ijH s tc l m men to ra my pht th i cho dao ng my
pht th j.
u im ca phng php ny l n gin, v h s khuch i c chn, cc
tham s khc ca PSS nh: khu lc thng cao, khu b pha,tnh ton d dng, ng
thi h s khuch i KPSS c th c iu chnh thch hp thng qua di tn s.
Nhng c nhc im l khi phn tch gi tr ring ca dao ng cc b v
dao ng lin khu vc mch vng kn th s khng y , nn khi iu chnh h
s khuch i gp nhiu kh khn khin gc ti vn c th dao ng.
1.5.1.2. Phng php tip cn p ng tn s
Phng php tip cn p ng tn s c bit n, bi nhiu tc gi
nghin cu thit lp cc tham s ca PSS. Trong k thut Nyquist c p
dng thit k b iu khin phn hi tc v cng sut cho h s khuch i.
Ni dung ca phng php l lp i lp li cc iu kin hot ng khc nhau
v h s khuch i c chn t khong trn. Mc ch chnh l xem xt c tnh
pha ca mt PSS, m hnh ha s tr pha ca hm truyn ( )PSSG s , phn hi mt
cch chnh xc cc pha tr trong hm truyn ca HTKT. Vi h thng nhiu my
pht, cc tham s ca khi tr pha v h s khuch i c c bng cch thit lp
cc phng trnh phi tuyn. tnh c cc tham s ta phi thit lp ba
phng trnh phi tuyn, c gii bng phng php Newton.
u im ca phng php ny l c th b pha mt cch chnh xc, h s
khuch i c xem xt trong trng hp c nhiu trong thc t.
Nhc im ca phng php l vic gii phng trnh phi tuyn s gp kh
khn, v phi lp th qu o nghim xt xem h c n nh hay khng, t
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tm cc h s cng gp nhng kh khn nht nh. gii quyt kh khn ny ta s
dng phng php gi tr ring v bin trng thi.
1.5.1.3. Phng php tip cn gi tr ring v bin trng thi
Phn tch gi tr ring l phn chnh ca cc nghin cu lin quan n n nh
tn hiu nh. Phng php ny c s dng rng ri trong vic iu chnh v phn
tch s lm vic ca PSS trong h thng c nhiu my pht. Tnh nng ca gi tr
ring c kt lun chung chung, nhng n khng b gii hn bi s phc tp ca
m hnh.
c PSS, ta s to ra mt cu trc iu khin ij ijPSSijG s k H s m s
lin kt u ra th j vi u vo th i ca h thng ijG s . Gi thit rng, nh my
b tc ng vi kiu dao ng c in h . nhy ca gi tr ring ngha l khi
thay i gi tr ring h cho ta mt thay i nh ca h s khuch i ijk , c th
hin bng cng thc sau:
ij ijij
hh hR Hk
(1.3)
trong ijhR l phn d ca kiu dao ng th h, c ngha l kt qu ca
phng php iu khin v phng thc quan st c miu t trc . M rng
phng trnh (1.3) vi h MIMO c th c vit nh sau:
ij
hh htrace R Hk
(1.4)
i vi nhng thay i nh ca ijk trong h s khuch i ijk , s thay i
gi tr h l ij ij
ij ijhh hR H k (1.5)
T biu thc (1.5) chng ta thy pha ca ijH iu khin hng thay i ca
gi tr ring h v ci thin h s ijk . Pha ca ijH s c chn nh hng ti
phn m ca mt phng phc, gi tr ring c th dch chuyn v bn tri bng cch
tng h s khuch i t c m men damping trong vng lp kn mong mun.
Khi gii phng trnh (1.5) s cho cu trc iu khin phn cp, v d khi ma trn
iu khin l ma trn ng cho. Mc d u ra ca mt b iu khin (gi l i)
iu khin mt bin u vo vt l no , nhng iu ny nh hng ti cc u ra
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khc (bn cnh i) bi v cc mi lin kt trong my pht in thng qua li in.
S thay i gi tr ring tng th lin quan n h s khuch i ca b iu khin
c la chn cung cp cho tt c cc vng lp. Hot ng ca s thay i h s
khuch i iik th hin nh sau:
ij ii ii1
n jih hh
jR H k
(1.6)
Gi tr thay i ca h
lin quan n b iu khin n l:
ij ii ii1 1
n n jih hh
i jR H k
(1.7)
Nghin cu phng trnh (1.6) ta thy pha ca iiH s c chn to ra m
men damping vi ch h thng qua iiG s ph hp vi h s khuch i iik . Pha
v h s khuch i ca thnh phn iiR gip ta la chn c tnh pha v h s
khuch i ca b iu khin mt cch tt nht. H s ca ma trn ijhR , ngay c
trong cu trc iu khin phn cp, cng cho bit cc vng lp khc nhau. Mt s
h s c th lm gi tr ring dch sang bn phi, kt qu cho thy m men damping
quan st c khc nhau ng k t cc gi tr thay i ny.
1.5.2. Cc cng trnh nghin cu v PSS
c rt nhiu cc cng trnh nghin cu v PSS, nhng a s u tp trung
vo phng php la chn tham s cho PSS theo cu trc cng c (chun IEEE).
Chng hn nh chn tham s ti u H cho PSS [15], [28], [36]; p dng chun H2
chn tham s cho PSS [20], [23]. Ngoi ra mt s tc gi cn nghin cu thit
k PSS c tnh tch hp cc yu cu nh thay i cc thng s, hoc thay i iu
kin lm vic c c m hnh ging nh min tn s thng qua hm hiu chnh
b ph hp, mc tiu l thu c p ng mong mun ca h thng. Phng php
thit k PSS bn vng s dng cu trc phn tch chn tham s cho PSS
c thng bo [16], [44]. Hm truyn vng h gia u ra ngoi sinh i vi nhiu
c nh dng bng cc b lc trng s iu khin. iu ny c bit n
nh iu khin loopshaping [37] bi ton ti u ny c gii bi k thut DK
interaction [47] trong Matlab. S thnh cng ca cc phng php trn da nhiu
vo vic la chn cc trng s, tuy nhin khng a ra mt lut r rng no p
dng cho sau ny.
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Nu nh vic gii cc bi ton iu khin ti u gp nhng gii hn th cch
tip cn chun H gii bt ng thc ma trn tuyn tnh (LMI) c th c p
dng. S tin li ca k thut ny l n c th s dng cho nhiu mc ch iu
khin khc nhau, chng hn nh nhiu c lc bng iu khin ti u cng bc
H thng qua H2 v gn im cc thng qua LMI. Ngoi ra c th kt hp vi nhau
bng k thut iu khin cn ti u. iu khin cn ti u thng qua cch tip cn
LMI c ng dng cho thit k PSS bn vng bng c trng thi lm vic v
phn hi u ra, c thng bo trong cc ti liu [18], [21], [50].
Gn y, vi s pht trin ca k thut iu khin thng minh v kh trnh,
nh thut ton di truyn, mng neural v logic m gii quyt c mt s cc bi
ton t ra trong k thut. Thut ton di truyn c s dng thit k PSS dp tt
cc dao ng gc rotor c thng bo trong ti liu [53]. K thut mng neural
nhn to c s dng thit k iu chnh tham s cho PSS [54]. Phng php
thit k PSS theo l thuyt h m cng c ng dng bi cng trnh ca Hariri
v Malik nm 1996 [24], hay cng trnh ca Hosseinzadeh, N. [26] nm 1999.
1.6. Hng nghin cu ca lun n
Cc phn tch trn cho thy rng, c kh nhiu cc lun im ring r cho
vic chn tham s ca PSS vi cu trc nh trc v cc tham s PSS hin ang s
dng cha phi l tt nht. Cng nh vy, cu trc cc PSS ang dng cha phi l
ti u v sch lc thit k PSS ti u cu trc cha c mt nghin cu no. V
vy, lun n t ra nhim v nghin cu thit k cu trc PSS ti u trn c s l
thuyt RH ri t th nghim nh gi, so snh cht lng vi PSS c cu trc
chun ang s dng hin nay.
L thuyt iu khin ti u RH (iu khin bn vng) lin quan ti bi ton
iu khin m i tng c cha nhng thnh phn bt nh khng xc nh c,
chng hn nh sai lch m hnh i tng v nhiu. Khc vi iu khin thch nghi,
cc thnh phn bt nh ca iu khin bn vng phi tha mn gi thit l b
chn v b iu khin bn vng khng cn phi t chnh nh li chnh mnh. c
nhng phng php iu khin bn vng khng s dng l thuyt ti u, v d nh
iu khin bn vng loop shaping, iu khin bn vng theo nguyn l Kharitonov.
Nhng cng c nhng phng php iu khin bn vng c s dng l thuyt ti u
vi mc ch nng cao cht lng bn vng ca h thng ti mc tt nht. iu
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khin bn vng RH l mt trong s . N c nhim v iu khin n nh h
thng bn vng vi sai lch m hnh v bn vng vi nhiu. Ngoi ra cht lng n
nh li t nhy cm nht vi sai lch m hnh v nhiu, iu m cc phng php
iu khin khc khng c.
B iu khin RH xut trong lun n ny khng thay th bt c mt b
iu khin no c trong HT ngoi tr PSS. C th, n khng thay th b
turbine & iu tc, b kch t & AVR, b gii hn in p,... N ch c b sung
thm vo HT nh mt PSS ti u tham s v cu trc dp tt cc dao ng gc
rotor ca my pht in. Cc dao ng ny c tn s khong 0,1 2Hz v l h qu
ca vic thiu thnh phn m men damping hay do phn ng qu nhanh ca HTKT.
Tnh ti u ca b iu khin RH ny nm ch s nh hng ca vic b sung
b iu khin RH ti nhng b iu khin khc, cng nh cht lng ng hc
c ca h thng l nh nht.
1.7. Kt lun chng 1
- Trong chng ny trnh by tng quan vn iu khin HT nh iu
khin in p, iu khin tn s v c bit l vn iu khin dp cc dao ng
gc rotor ca my pht in.
Phn tch nguyn nhn gy ra dao ng, tc hi ca dao ng v bin php
khc phc. T a ra vn s dng b n nh HT PSS hot ng thng qua
AVR dp tt cc dao ng gc rotor ca my pht in.
Phn tch cc vn nghin cu v PSS, bao gm cc phng php tip cn
thit k PSS nh m men damping, p ng tn s hay gi tr ring v ma trn trng
thi; cng nh phn tch cc tn ti v nghin cu cn b ng.
Trn nn l thuyt ti u RH tc gi t ra nhim v thit k b iu
khin PSS bn vng, c tnh ti u c v cu trc v tham s, thay th cho cc
PSS hin c. thc hin c mc ch t ra , trc ht ta phi xy dng c
m hnh ton tng qut ca trm pht in v cc phn t c lin quan. y l tin
quan trng p dng l thuyt ti u RH vo thit k b iu khin PSS.
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2 Chng 2. M HNH TON CA TRM PHT IN
TRONG H THNG IN
My pht in xoay chiu c tc quay rotor n bng tc quay ca t
trng n1 gi l my pht in ng b. ch xc lp, my pht in ng b
c tc quay rotor lun khng i khi ti thay i.
My pht in ng b l ngun in chnh ca cc li in cng nghip,
trong ng c s cp l cc turbine hi, turbine kh hoc turbine thy lc. Vi
cng ngh ch to hin i, cng sut ca mi t my c th t ti hng trm MW
hoc ln hn. Cc my pht in thng c s dng lm vic song song vi
nhau, nhng cng c th lm vic c lp trong cc li in c cng sut nh.
My pht in ng b ng b gm hai b phn chnh l stato v roto. Stator
ca my pht in ng b cng ging nh stator ca my in khng ng b gm
hai b phn chnh l li thp stator v dy qun ba pha stator. Li thp stator c
p bng cc l tn Silic dy khong 0,5mm, hai mt c ph lp sn cch in v
dc chiu di ca li thp c cc rnh thng gi t nm ngang trc lm mt. Li
thp stator c t c nh trn thn my. Dy qun stator cn gi l dy qun
phn ng v c t trong cc rnh ca stator.
Rotor my pht in ng b c cc cc t v dy qun kch t. C th phn
rotor thnh hai loi chnh: rotor cc n v rotor cc li [1], [13].
Cc t nm pha ngoi ca rotor, chng thng phi chu lc ly tm ln.
hn ch tn tht do dng in r trn cc t, chng c ch to bi cc l thp vi
c tnh t ho tt. Tu thuc vo tc quay ca rotor (n) v tn s dng in
stator (f) m s cc t c xc nh bi [30]:
120f
pn
Equation Section 2 (2.1)
Vi cc my pht in cng sut ln trn b mt pha u cc t c gn thm
cun cn (damper). Thanh dn bng ng hoc ng thau c s dng ch to
cun cn tu thuc vo mc ch s dng. Cc thanh cn c ni vi cc b phn
cun cn (cc vng ngn mch, cc vng ai) bng cc mi hn bc hoc ng thau
gim in tr tip xc v tng bn c kh. Nhim v ca cun cn l: ngn
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chn dao ng ca my pht do s thay i t ngt ca ph ti, in p v tn s
h thng; to ra m men khi ng ging cun dy ca ng c cm ng rotor lng
sc; ngn chn sng hi bc cao to ra t phn ng phn ng do ti khng i xng.
S khi ca mt my pht nh hnh 2.1. in nng c to ra bi my pht
ng b bng cch iu khin b iu tc s cp, thng thng l turbine hoc ng
c diezen. Turbine c lp t vi b iu tc c nhim v iu khin tc hoc
cng sut u ra da trn c tnh cng sut tn s. Cng sut my pht c pht
ln li in thng qua MBA tng p. Dng in hoc in p mt chiu to ra t
thng trong my pht c cung cp bi my kch t, dng in kch t c iu
khin bi b t ng iu chnh in p AVR. Mt MBA c th c thm vo
gia MBA tng v my pht nhm cung cp cng sut cho cc thit b ca nh my
nh ng c my nn, my bm, my kch t, My pht cng c lp t vi
my ct chnh pha cao p, my ct u cc tng tnh linh hot trong vn hnh.
Li in
Turbine
Van/c
ng
cnh h
ng
My ct
My bin p tng
My ct
Cc thit b o lng
My pht in
Kch t
AVR
iu tc
P
f
Vref
Pref
Nhi
n li
u v
o
My bin p
Cung c
p t
i
ngu
n p
h
Vt
It
+
_
Efd
VR
Trc
Hnh 2.1. S khi mt my pht in ng b
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Trong my pht in ng b hai cc t nh hnh 2.2, trc dc d l trc ca
cc bc N. Trc ngang q vt trc trc d mt gc 900 in. Trong iu kin
khng ti, khi trong my ch c t trng kch thch, sc t ng ca t trng s
hng theo trc d v sc in ng ca dy qun stato s hng dc trc q. M
hnh my pht c xy dng trong phn ny da trn khi nim my in ng
b l tng c hai cc t, b qua cc sng t trng bc cao c nh hng n
cc c tnh ca my v cho rng rnh ca stator khng nh hng n in khng
ca rotor d v tr gc ca n nh
th no. Mc d s bo ha mch
t khng c tnh n mt cch
r rng trong m hnh ny nhng
ta c th hiu chnh in khng
theo hai trc bng h s bo ha
hay a thm phn t b vo t
trng kch thch.
2.1. M hnh my pht in ng b
Hnh 2.2 l s n gin
ca my in hai cc t vi cun dy kch t, c ba cun cn trn rotor (mt cun
dc trc, hai cun ngang trc), cc cun dy stator c trc lch nhau 1200 in, k
hiu dng in i vo l v i ra l Mc d hnh 2.2 biu din s my
in hai cc t, nhng tt c c phng trnh sau ny u c vit cho my in c
p cc t vi tc 2m
p [46].
Theo nh lut Kirchhoff, Faraday v Newton ta c cc phng trnh i s.
aa s a
dv r i
dt
(2.2)
bb s b
dv r i
dt
(2.3)
cc s c
dv r i
dt
(2.4)
Trc pha a
Trc pha b
Trc pha c
Trc d
Trc q
1d fd
c
b
a
1q 2q
Hnh 2.2. S my in ng b hai cc t
N
S
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fdfd fd fd
dv r i
dt
(2.5)
11 1 1
dd d d
dv r i
dt
(2.6)
11 1 1
qq q q
dv r i
dt
(2.7)
22 2 2
qq q q
dv r i
dt
(2.8)
2d
dt p
(2.9)
2m e fw
dJ T T Tp dt
(2.10)
trong :
t thng mc vng
r in tr cun dy
J hng s qun tnh
p s cc t
Tm m men c ca trc
Te m men in
Tfw m men ma st khe h khng kh (friction windage)
2.1.1. Phng trnh biu din trn h trc to dq0
Trong cc phng trnh biu din ng hc ca my in ng b, ngi ta
hay biu din trn h ta dq0. chuyn t cc bin pha a, b, c sang cc bin
dq0 ta ng dng php chuyn i h ta ca Park [29].
0 0 0 0 0 0, , dq dq abc dq dq abc dq dq abcv T v i T i T (2.11)
trong :
[ ] , [ i ] , [ ]T T Tabc a b c abc a b c abc a b cv v v v i i i (2.12)
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0 0 0 0 0 0[ ] , [ ] , [ ]T T T
dq d q dq d q dq d qv v v v i i i i (2.13)
v
0
2 2sin sin( ) sin( )
2 2 3 2 3
2 2 2cos cos( ) cos( )
3 2 2 3 2 3
1 1 1
2 2 2
dq
p p p
p p pT
(2.14)
o ngc ta c
0
1
sin cos 12 2
2 2sin( ) cos( ) 1
2 3 2 3
2 2sin( ) cos( ) 1
2 3 2 3
dq
p p
p pT
p p
(2.15)
t (2.2) (2.10) ta c
( )abc s abc abcd
v r idt
(2.16)
s dng php bin i (2.14) v (2.15), ta c
0
10 0 0 0( )dqdq s dq dq dq
dv r i T T
dt (2.17)
Sau khi bin i, ta c cc phng trnh my in biu din trong h dq0 nh sau
dd s d q
dv r i
dt
(2.18)
qq s q d
dv r i
dt
(2.19)
00 0s
dv r i
dt
(2.20)
fdfd fd fd
dv r i
dt
(2.21)
11 1 1
dd d d
dv r i
dt
(2.22)
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11 1 1
qq q q
dv r i
dt
(2.23)
22 2 2
qq q q
dv r i
dt
(2.24)
2d
dt p
(2.25)
2m e fw
dJ T T Tp dt
(2.26)
Mt khc, m men in li c tnh theo [30], [46]
3( )
2 2e q d d q
pT i i (2.27)
gc rotor
02
pt (2.28)
suy ra
0
d
dt
(2.29)
Cui cng ta c m hnh my pht in ng b vi cc bin mi va nh ngha l
ds d q d
dr i v
dt
(2.30)
qs q d q
dr i v
dt
(2.31)
00 0s
dr i v
dt
(2.32)
fdfd fd fd
dr i v
dt
(2.33)
11 1 1
dd d d
dr i v
dt
(2.34)
11 1 1
qq q q
dr i v
dt
(2.35)
22 2 2
qq q q
dr i v
dt
(2.36)
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0
d
dt
(2.37)
2 3( )
2 2m q d d q fw
d pJ T i i Tp dt
(2.38)
Thng thng, ta hay s dng cc phng trnh my in ng b trong h
n v tng i. Bi vy, sau khi k hiu li cc bin mi trn c s cc bin ban
u, ta c cc phng trnh nh sau
0 0
1 ds d q d
dR I V
dt
(2.39)
0 0
1 qs q d q
dR I V
dt
(2.40)
00 0
0
1s
dR I V
dt
(2.41)
0
1 fdfd fd fd
dR I V
dt
(2.42)
11 1 1
0
1 dd d d
dR I V
dt
(2.43)
11 1 1
0
1 qq q q
dR I V
dt
(2.44)
22 2 2
0
1 qq q q
dR I V
dt
(2.45)
0
d
dt
(2.46)
0
2( )M d q q d FW
H dT I I T
dt
(2.47)
2.1.2. Phng trnh vi mch t tuyn tnh
Trong trng hp ny t thng ca my in l hm tuyn tnh ca dng in:
( ) ( )abc ss shaft abc sr shaft rotorL i L i (2.48)
( ) ( )rotor rs shaft abc rr shaft rotorL i L i (2.49)
trong :
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1 1 2 1 1 2[ ] , [ ]T T
rotor fd d q q rotor fd d q qi i i i i (2.50)
chuyn sang h trc dq0 theo (2.11) v sau cc bin i ta c
0 0
1 ds d q d
dR I V
dt
(2.51)
0 0
1 qs q d q
dR I V
dt
(2.52)
00 0
0
1s
dR I V
dt
(2.53)
0 12( )[ (
( )
( ) )]
q d dd fd q d d d d
d ls
d ls d q
dE X XT E E X X Idt X X
X X I E
(2.54)
10 1 ( )
dd d q d ls dd
T E X X Idt
(2.55)
0 22( )[ (
( )
( ) )]
q qdq d q q q q
q ls
q ls q d
X XdET E X X Idt X X
X X I E
(2.56)
20 2 ( )
qq q d q ls q
dT E X X I
dt
(2.57)
0
d
dt
(2.58)
0
2( )M d q q d FW
H dT I I T
dt
(2.59)
/
1d ls d d
d d d q dd ls d ls
X X X XX I E
X X X X
(2.60)
/
2q ls q q
q q q d qq ls q ls
X X X XX I E
X X X X
(2.61)
0 0lsX I (2.62)
Trong cc phng trnh trn mi quan h gia 0 0, , , , , d d q qV I V I V I vn
cha xc nh, do cn gi li ba phng trnh i s t thng c lin quan n
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, d qI I v 0I . Thm vo cc bin , fd ME T v FWT cng cha xc nh. l l
do gi thit fdE , MT l nhng tn hiu vo hng s v 0FWT .
Nh vy m hnh ng hc ca my pht in ng b biu din theo (2.51)
(2.62), nu s bo ho ca mch t khng xem xt n.
2.2. M hnh kch t v b iu chnh in p
Nh trnh by trong mc 1.2.2.1. trng thi tnh, vic iu chnh in p
kch t s thay i c dng in kch t v do thay i in p u cc my pht.
y ta ch quan tm ti m hnh ton hc ca n. Ta xem xt hai trng hp sau:
Kch t mt chiu c lp
ng hc mch t cho bi
11 1 1
fin f in
de r i
dt
(2.63)
1 1 1fd s sv K (2.64)
hay
1 1us1 1
1 1
( )f f fd
in fd f sat fd fdg g
r L dve v r f v v
K K dt (2.65)
sau khi t tn cc bin mi v chuyn sang n v tng i [46], ta c m hnh
kch t mt chiu c lp:
[ ( )]fd
E Esep E fd fd R
dET K S E E Vdt
(2.66)
trong :
VR in p u vo my kch t (in p u ra AVR)
vfd
+
+
ein1
rf1
Lf1
iin1
Hnh 2.3. S mch my kch t mt chiu c lp
+
1 1 1s sK
rs Ls1
Phn ng
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( )E fdS E hm bo ho
1
1
fEsep
g
rK
K
1gK h s gc ng tip tuyn vi ng cong bo ho mch t
Kch t mt chiu t kch thch
Khi my pht mt chiu chnh dng lm my kch t t kch, th n c xem
nh mc ni tip vi mch t nh hnh 2.4. Phng trnh ng hc mch t s l
11 1 1
fin f in fd
de r i v
dt
(2.67)
chuyn sang h n v tng i [46], ta c
[ ( )]fd
E Eself E fd fd R
dET K S E E Vdt
(2.68)
trng thi xc lp, phng trnh kch t c th vit
[ ( )] 0R E E fd fdV K S E E (2.69)
Tn hiu u vo RV thng c ci t gi tr ln nht RmaxV s to ra
in p kch t ln nht fdmaxE v phi tho mn phng trnh
( ) 0Rmax E Emax fdmaxV K S E (2.70)
M hnh b iu chnh in p AVR
RA R A indV
T V K Vdt
(2.71)
min maxR R RV V V (2.72)
vfd
rf1
ein1
+
Hnh 2.4. S mch my kch t t kch
+
Lf1
rs1
Ls1
iin1
1 1 1s sK
+
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trong :
Vin in p u vo AVR
TA hng s thi gian AVR
KA h s khuch i
VR in p u vo ca my kch t chnh, in p ny c th c gi tr bt
k gia 0 v gi tr gii hn ca n nu my kch t chnh l t kch, nhng phi
khc khng nu my kch t l kch t c lp.
M hnh ng hc ca mch n nh kch t
( )E E fd RFF F F fd
E E
K S E VdVT V K Edt T T
(2.73)
mt dng khc ca m hnh ny hay c s dng [46]
Ff fd F
F
KR E V
T (2.74)
vi fR nh trng thi ng hc
f FF f fd
F
dR KT R Edt T
(2.75)
s dng quan h (2.76) thay vo (2.71) ta s c m hnh y ca kch t v
AVR l cc phng trnh (2.77) (2.80)
Fin ref t f fd ref t F
F
KV V V R E V V V
T (2.76)
Vy, m hnh ng hc kch t v AVR s l:
[ ( )]fd
E E E fd fd R
dET K S E E Vdt
(2.77)
f FF f fd
F
dR KT R Edt T
(2.78)
( )R A FA R A f fd A ref tF
dV K KT V K R E K V Vdt T
(2.79)
min maxR R RV V V (2.80)
hoc c th s dng cc phng trnh (2.77), (2.73) v phng trnh
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( )RA R A F A ref tdV
T V K V K V Vdt
(2.81)
Cc phng trnh (2.73), (2.77) v (2.81) c s khi nh hnh 2.5.
2.3. M hnh turbine v b iu chnh tc
2.3.1. M hnh turbine
a) Turbine thu lc
Nh my thu in c nm thnh phn chnh, l: h cha, ng ng dn
nc, p dng nc, ng ng p lc v turbine thy lc. M hnh phi tuyn ca
cc thnh phn ny thng khng c s dng trong cc phn tch ng hc ca
HT v n phc tp. Thay vo cc m hnh xp x tuyn tnh c s dng c
c c tnh c bn ca nh my in v nhng nh hng ca n n HT.
M hnh turbine thu lc trong h n v tng i c dng (ch c gi tr vi
nhng thay i nh xung quanh im lm vic):
23 13 2123
11 11 11
1HT HVw HT HV w
A A AdT dPT T P T Adt A A A dt
(2.82)
0HT
HT
d
dt
(2.83)
0
2 HT HTHT M
H dT T
dt
(2.84)
( )M HM HTT K (2.85)
trong :
HTT m men u ra ca turbine thu lc
1
A
A
K
sT
1
E EK sT
Vref VR Efd
Vt
Hnh 2.5. M hnh HTKT IEEE loi 1 [46]
( )E fdS f E
+
1
F
F
sK
sT
VF
+
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HVP cng sut mc nc tc nh mc (ng vi mt v tr ca cng
cnh hng)
Tw hng s thi gian bt u (0,5 5s)
HT tc ca turbine thu lc
HTH hng s qun tnh ca turbine thu lc
Khi s dng m hnh my pht in ng b, ngui ta thng s dng m
men trong phng trnh chuyn ng. V my pht v turbine i i vi nhau thng
qua gc rotor v gc HT , cng sut thu PHV s tr thnh mt trng thi ng
hc. Khi lin kt cng vi nhau, THV tr thnh TM v hng s turbine tr thnh hng
s qun tnh my pht. Do , ta c phng trnh:
23 13 2123
11 11 11
1M HVw M HV w
A A AdT dPT T P T Adt A A A dt
(2.86)
b) Turbine hi
Trong m hnh ny ta quan tm ti nh hng ca v tr van (cng sut PSV) ti
m men ca my pht ng b TM.
1 HP RH HP RHMRH M CH SVCH CH
K T K TdTT T P K
dt T T
(2.87)
CHCH CH SV
dPT P P
dt (2.88)
trong :
PCH cng sut u ra ca ng ng hi
PSV v tr van turbine (cng sut)
v MT l mt trng thi ca my pht ng b khi turbine v my pht ni vi nhau.
i vi h thng khng c gia nhit, n gin cho 0RHT vo (2.87)
(2.88) v ta c c m hnh sau y
MCH M SV
dTT T P
dt (2.89)
v SVP s tr thnh mt trng thi khi b iu tc c thm vo.
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2.3.2. M hnh b iu tc
C rt nhiu h thng iu tc turbine [10], [33], chng hn nh loi c kh
thy lc (hnh 2.6) nhng loi ny ang dn c thay th bng loi in t thy
lc (hnh 2.7).
M hnh b iu tc bao gm khu gii hn v tr van l
0
11SVSV SV C
D
dPT P P
dt R
(2.90)
0SV
maxSVP P (2.91)
trong :
PC cng sut t u vo (c th l mt hng s)
RD tc iu chnh (%)
M hnh trn tng ng vi m hnh ca hng General Electric.
Kt lun: M hnh ng hc turbine v b iu tc s l:
MCH M SVdT
T T Pdt
(2.92)
B bin i in t - thy lc
Pilot valve
Hnh 2.7. S khi ca h thng iu tc in t - thy lc
Ti t
Phn hi dng hi
B iu chnh
in t
p sut hi
Servor motor
valve
ref Phn hi
V tr
va
n
Pilot valve
Hnh 2.6. S khi ca h thng iu tc c kh - thy lc
Ti t
iu tc ly tm
Servor motor
valve
Phn hi
V tr
va
n
ref
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0
11SVSV SV C
D
dPT P P
dt R
(2.93)
0SV
maxSVP P (2.94)
Cc phng trnh (2.92) (2.94) c s khi nh hnh 2.8
2.4. M hnh ca h my pht kt ni vi HT
2.4.1. Phng trnh rng buc in p trong h n v tng i
Khi my pht in kt ni vi HT ta c phng trnh rng buc in p
0 0
1sin( )edd e d eq s vs
dV R I V
dt
(2.95)
0 0
1( )
eqq e q ed s vs
dV R I V cos
dt
(2.96)
00 00
1 ee
dV R I
dt
(2.97)
vi
( )ed ep dX I (2.98)
( )eq ep qX I (2.99)
0 0 0( )e eX I (2.100)
sV l in p trn thanh ci h thng c n v l p.u, v tt c cc i lng
khc tng ng vi lng nh mc ca my pht.
1
DR 1
1 SVsT 1
1 CHsT
PC - ti t
PSV TM
Hnh 2.8. M hnh h thng turbine v iu tc n gin
+ _ ref
_
+
Turbine iu tc
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2.4.2. M hnh multitimescale ca h my pht kt ni vi HT (m hnh bc 8)
Trong phn ny ta s nghin cu trng hp ca mt my pht kt ni vi
thanh ci ca HT, s dng m hnh my pht (2.51) (2.62), m hnh kch
t/AVR (2.77) (2.80) khng c b b ti, m hnh turbine/iu tc (2.89) (2.91),
phng trnh rng buc in p u cc (2.95) (2.97) v (2.98) (2.100)
Trc ht t
0( )t sT tc tc thi (2.101)
0
2s
HT
hng s thi gian c (2.102)
0
1
(2.103)
kt hp t thng my pht vi ng dy cng nh cc thng s khc:
0 0 0, ,
, ,
, ,
, X
de d ed qe q eq e e
de d e qe q e de d e
qe q e de d e qe q e
se s e lse ls e
X X X X X X X X X
X X X X X X X X X
R R R X X
(2.104)
Thay phng trnh (2.95) (2.97) vo (2.51) (2.62) v thm vo cc m
hnh ng hc khc ta c
1 sin( )de se d t qe s vss
dR I V
dt T
(2.105)
1 cos( )qe
se q t de s vss
dR I V
dt T
(2.106)
0 0e
sed
R Idt
(2.107)
0 12( ) ( ( )( )
q d dd fd q d d d q d ls d q
d ls
dE X XT E E X X I X X I E
dt X X
(2.108)
10 1 ( )
dd d q d ls dd
T E X X Idt
(2.109)
0 22( ) ( ( )( )
q qdq d q q q q q ls q d
q ls
X XdET E X X I X X I E
dt X X
(2.110)
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20 2 ( )
qq q d q ls q
dT E X X I
dt
(2.111)
s td
Tdt
(2.112)
( )ts M de q qe d FWd
T T I I Tdt
(2.113)
1( ) ( )
( ) ( )
d ls d dde de d q d
d ls d ls
X X X XX I E
X X X X
(2.114)
2( ) ( )
( ) ( )
q ls q qqe qe q d q
q ls q ls
X X X XX I E
X X X X
(2.115)
0 0 0e eX I (2.116)
[ ( )]fd
E E E fd fd R
dET K S E E Vdt
(2.117)
f FF f fd
F
dR KT R Edt T
(2.118)
( )R A FA R A f fd A ref tF
dV K KT V K R E K V Vdt T
(2.119)
min maxR R RV V V (2.120)
2 2t d qV V V (2.121)
1 sin( )edd e d t eq s vss
dV R I V
T dt
(2.122)
1 ( )eq
q e q t ed s vss
dV R I V cos
T dt
(2.123)
ed ep dX I (2.124)
eq ep qX I (2.125)
MCH M SVdT
T T Pdt
(2.126)
SV tSV SV C
D s
dPT P P
dt R T
(2.127)
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0SV
maxSVP P (2.128)
Trong cc phng trnh trn, qu trnh qu stator ca de v qe din ra
rt nhanh so vi cc ng hc khc. T thng mc vng cun cn 1d v 2q din ra
cng kh nhanh, v 0dT v 0qT thng thng kh nh. Cc thnh phn Efd v VR c
xu hng nhanh bi v TE v TA thng l nh. Cc thnh phn cun dy kch t
qE v thnh phn phn hi Rf c xu hng chm bi v 0dT v FT kh ln. Cc
trng thi turbine/iu tc TM, PSV c xu hng chm bi v TCH v TSV kh ln.
T thng mc vng cun cn dE c th nhanh hoc chm, da trn 0qT . M hnh
h my pht kt ni vi HT trn cn gi l m hnh bc 8 [9].
c tnh ng hc ca mi m hnh l rt quan trng, v n xc nh kch
thc bc dng trong m phng thi gian thc. Nu mt m hnh c c tnh ng
hc nhanh th cn thit phi c kch thc bc nh. Trng hp hin tng quan
tm trong min thi gian vi p ng chm v trung bnh, th c th b qua ng
hc nhanh. Sau y ta xt mt s trng hp m ng hc nhanh c b qua t
gip ta la chn ra m hnh ph hp vi mc ch nghin cu.
2.4.3. M hnh b qua qu stator ca h my pht kt ni vi HT (m hnh bc 6)
M hnh ny tng t nh m hnh trn, ngoi tr qu trnh qu stator c
cho l din ra rt nhanh v tng ng vi cc dao ng rotor chm. Mch thay th
ng hc vi ngun in p t sau in khng dX c trnh by trn hnh 2.9
0 12( ) ( ( )( )
q d dd fd q d d d d d ls d q
d ls
dE X XT E E X X I X X I E
dt X X
(2.129)
jXd
+
+
+
Rs Re jXe
vsjsV e
( /2)( ) jd qI jI e
( /2)( ) jd qV jV e
Hnh 2.9. S ng hc siu qu ca my pht [46]
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10 1 ( )d
d d q d ls dd
T E X X Idt
(2.130)
0 22( ) ( ( )( )
q qdq d q q q q q ls q d
q ls
X XdET E X X I X X I Edt X X
(2.131)
20 2 ( )
qq q d q ls q
dT E X X I
dt
(2.132)
0
d
dt
(2.133)
10
2
2
( )
d ls d dM q q d q
d ls d ls
q ls q qd d q d q d FW
q ls q ls
H d X X X XT E I I
dt X X X X
X X X XE I I X X T
X X X X
(2.134)
[ ( )]fd
E E E fd fd R
dET K S E E Vdt
(2.135)
f FF f fd
F
dR KT R Edt T
(2.136)
( )R A FA R A f fd A ref tF
dV K KT V K R E K V Vdt T
(2.137)
MCH M SVdT
T T Pdt
(2.138)
0
11SVSV SV C
D
dPT P P
dt R
(2.139)
vi cc iu kin rng buc
min axR R R mV V V (2.140)
ax0
SV mSVP P (2.141)
v cc phng trnh i s tm Id, Iq
2( ) ( ) sin( ) 0
q ls q qs e d q e q d q s vs
q ls q ls
X X X XR R I X X I E V
X X X X (2.142)
1( ) ( ) cos( )
d ls d d
s e q d e d q d s vsd ls d ls
X X X XR R I X X I E V
X X X X (2.143)
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thay vo 2 phng trnh (2.144) (2.145) tm Vd, Vq
sin( )d e d e q s vsV R I X I V (2.144)
cos( )q e q e d s vsV R I X I V (2.145)
cui cng
2 2t d qV V V (2.146)
2.4.4. M hnh two-axis ca h my pht kt ni vi HT (m hnh bc 4)
Ta thy trong cc phng trnh trn vn cn cha ng hc cun cn 1d v
2q . Nu 0dT v 0qT nh, ta s c s ng hc hai trc ca my pht in
ng b nh hnh 2.10 vi cc phng trnh
0 ( )q
d fd q d d d
dET E E X X Idt
(2.147)
0 ( )d
q d q q qdE
T E X X Idt
(2.148)
0
d
dt
(2.149)
0
2( )M d d q q q d d q FW
H dT E I E I X X I I T
dt
(2.150)
( ( ))fd
E E E fd fd R
dET K S E E Vdt
(2.151)
f FF f fd
F
dR KT R Edt T
(2.152)
jXd
+
+
Hnh 2.10. M hnh hai trc (two-axis) ca h my pht [46]
+
Rs Re jXe
vsjsV e
( /2)( ) jd qI jI e
( /2)( ) jd qV jV e
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( )R A FA R A f fd A ref tF
dV K KT V K R E K V Vdt T
(2.153)
MCH M SV
dTT T P
dt (2.154)
0
11SVSV SV C
D
dPT P P
dt R
(2.155)
Cc iu kin rng buc
min axR R R mV V V (2.156)
ax0
SV mSVP P (2.157)
v cc phng trnh i s tm Id, Iq
( ) ( ) sin( ) 0s e d q e q d s vsR R I X X I E V (2.158)
( ) ( ) cos( ) 0s e q d e d q s vsR R I X X I E V (2.159)
thay vo 2 phng trnh (2.160) (2.161) tm Vd, Vq
sin( )d e d e q s vsV R I X I V (2.160)
cos( )q e q e d s vsV R I X I V (2.161)
cui cng l in p u cc
2 2t d qV V V (2.162)
2.4.5. M hnh fluxdecay ca h my pht kt ni vi HT (bc 3)
gim bc ca m hnh, trong cc phng trnh phn trc cn cha ng
hc cun cn dE . Nu 0qT nh ta s c c trng thi ng hc vi mong
mun gim bc ny.
Cho 0 0qT vo phng trnh (2.148) ta c
( ) 0d q q qE X X I (2.163)
Kh dE trong (2.147) (2.162), phng trnh Id v Iq tr thnh
( ) ( ) sin( ) 0s e d q e q s vsR R I X X I V (2.164)
( ) ( ) cos( ) 0s e q d e d q s vsR R I X X I E V (2.165)
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Cng nh cc phn trc, hai phng trnh thc c th vit di dng mt
phng trnh phc
( /2) ( /2)
( /2)
[( ) ] ( )( )
( )( ) vs
jq d q q s d d q
je e d q s
X X I jE e R jX I jI e
R jX I jI e V e
(2.166)
Cc phng trnh Vd v Vq tng t nh phn trc, bi vy s ng hc
ca m hnh fluxdecay my pht in ng b l hnh 2.11.
Dng cui cng ca m hnh fluxdecay m b qua ng hc ca tt c cc
cun cn, bng cch thay (2.163) vo (2.147) (2.162), kh i dE nh sau :
0 ( )q
d fd q d d d
dET E E X X Idt
(2.167)
0
d
dt
(2.168)
0
2( )M q q q d d q FW
H dT E I X X I I T
dt
(2.169)
[( ( )]fd
E E E fd fd R
dET K S E E Vdt
(2.170)
f FF f fd
F
dR KT R Edt T
(2.171)
( )R A FA R A f fd A ref tF
dV K KT V K R E K V Vdt T
(2.172)
MCH M SVdT
T T Pdt
(2.173)
jXd
+
+
+
Rs Re jXe
vsjsV e
( /2)( ) jd qI jI e
( /2)( ) jd qV jV e
Hnh 2.11. M hnh ng hc flux-decay ca my pht in [46]
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0
11SVSV SV C
D
dPT P P
dt R
(2.174)
Cc iu kin rng buc
min maxR R RV V V (2.175)
max0
SVSVP P (2.176)
v cc phng trnh i s (2.164) (2.165) tnh Id, Iq
sau thay vo 2 phng trnh (2.177) (2.178) tm Vd, Vq
sin( )d e d e q s vsV R I X I V (2.177)
cos( )q e q e d s vsV R I X I V (2.178)
cui cng l in p u cc
2 2t d qV V V (2.179)
Trong cc ti liu [9], [51] m hnh ny gi l m hnh bc 3; cn trong ti
liu [39] m hnh ny xp vo m hnh 3 (b qua nh hng ca cun cn).
2.4.6. M men damping
Trong cc phng trnh trn u xt n mt thnh phn m men ma st khe
h khng kh FWT . C chiu ngc vi chiu quay rotor, thnh phn m men ny
c dng [46]
FW FWT K (2.180)
Trong mt s ti liu, thnh phn ny c tnh n trong m men damping:
0( )D DT K (2.181)
M men damping c th dng hoc m tu vo tc my pht. Nu cun
cn c xt n thng qua cc phng trnh vi phn ca chng, th khng cn
tnh n trong m men damping DT na v ma st khng kh c m t thng qua
FWT . Trong cc m hnh fluxdecay hoc m hnh kinh in [30], [46] ca my
pht in th nh hng ca cun cn c b qua. Cn nh gi nh hng ca
cc cun cn m khng xt n cc phng trnh vi phn ca chng, ta cn thm
vo thnh phn FWT trong phng trnh ca m men damping DT .
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2.5. Kt lun chng 2
Trong chng ny ta xy dng c m hnh ton hc tng qut ca my
pht in ng b, kch t v AVR, turbine v iu tc.
M hnh ton hc ca my pht in ng b trong nghin cu n nh l kh
phc tp t bc 8, bc 6, bc 4, bc 3 vic chn m hnh no l cn ty thuc vo
chng loi my pht, quan im trong vn phn tch n nh. V ch h thng
in m ta ang xt l ch bnh thng nn tt c cc thng s u gn nh
mc, ta cng ch xt n nh hng ca cc nhiu nh. Do ta s dng m hnh
ton hc tng qut trong nghin cu l m hnh bc 3.
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3 Chng 3. PHN TCH B N NH H THNG IN PSS
Trong chng 1 gii thiu v khi nim PSS, chng 2 xy dng m
hnh ton hc ca my pht in v cc phn t lin quan di dng tng qut.
Trong chng ny ta phi xy dng m hnh ton hc tn hiu nh t nh gi
c nh hng ca PSS trong vic n nh gc ti.
3.1. Xy dng m hnh tn hiu nh ca h my pht kt ni vi HT
Trong nghin cu ny ta kho st s nguyn l ca mt my pht in n
ni vi thanh ci h thng cng sut v cng ln nh hnh 3.1, trong s khng cn
biu din b phn iu tc v p ng ca n tng i chm so vi p ng ca
HTKT. M hnh ton hc tng qut xem xt l m hnh fluxdecay nh trnh by
trong mc 2.4.5. Khi phn tch, in tr ng dy eR v in tr stator sR bng
khng; khng c ti trn thanh ci, gc pha u ca in p trn thanh ci 0vs .
Mc ch nghin cu l n nh tn hiu nh dp tt cc dao ng nn ta s
dng m hnh tuyn tnh ha xung quanh im lm vic.
Vit li cc phng trnh (2.167) (2.169), vi gi thit 0