8 . references 1) billinton 143 , no .2 , march 1996
TRANSCRIPT
8. REFERENCES
1) Billinton R. and Satish J.: 'Effect of rotational load shedding on overall
power system adequacy indices', lEE Proc-Gener. Transm. Distrib. Vol
143, No.2, March 1996.
2) Wong K.P. and Lau B.S. : 'Algorithm for load shedding operations in
reduced generation periods', lEE Proceedings-c. =Vol 139, No.6,
November 1992. 1
3) Billinton R. and Wang P. : 'Optimum load shedding technique to reduce
the total customer interruption cost in distribution system', lEE Proc
Gener. Transm. Distrib. Vol 147, No.1 , January, 2000.
4) Harrison P. : 'Considerations when planning a Load Shedding
Programme', Brown Bovery Rev. 67 1980(10) 593-599 .
.... 5) Berthold Vienna R. and Narayan V. : 'Load Shedding and Decoupling
Power Systems', Brown Bovery Rev. 6/7 1981 .
6) Relays and Protection Schemes, : 'Load Shedding to Influence
Frequency during Overload Condi'tion', BBC, Brown Bovery.
7) Udren E.A.,(Rivised by ; Elmore W.A.) : 'Load Shedding and
Frequency Relaying', Protective Relaying Theory and Applications,ABB
Power T&D Co. Inc., Relay division, Coral Springs, Florida.
8) Lewis Blackburn J.; 'Stability, Reclosing and Load shedding',
Protective Relaying Principles and Applications.
9) Daniel S. Kischen : 'Power System Security', Power Engineering
Journal, October,2002.
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING ALGORITHM 50 llG<Nml ~
'
& w. ......... ~~.it-
10) Wehenkel L.: 'Emergency control and its strategies', Web:
http://www.montefiore.ulq.ac.be
11) Intelligent Shedding Scheme for Distribution and Industrial Networks :
ABB Network Partner AG.
12) Long Term Transmission Development Plan, 2002-2011 , CEB
13) Protective Relays Application Guide; GEC ALSTHOM Ltd.
14) Micom P940 Series Relay Catalog, ALSTOM T&D Protection &
Control Ltd, UK. .I
15) SIPROTEC 7RW600 V1 Relay Catalog, SEIMENS AG, Germany.
16) Mathlab I Simulink Help Manuel
17) ECAR Document No.12: 'Automatic Load Shedding practices and
special protection systems', July 1998
18) Grid Code, Operating Code 5 ; 'Demand Control', Commission for
Electricity Regulation , January,2000.
19) NEMMCO's advice to the Reliability Panel, Version 1, July 2001
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING ALGORITHM 51
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9o2o APPENDIX 2; MATLAB/Simulink blocks
a) Transmission Line model
(:l unhlled o 1!11!1 £1 (:]Lonk: unhtled/loroHl o 1!1~ 13
fie ~dl Y.- ,SIIT'dobon Forma!
Tgola -----D j ~liiiB .lt~ft i !2
8 TC
c
Uno1
h.
Eie Eli Y.- .SmAaOOr!
Ready 75~
Dialog box for Transmission line model
ode.(5
Block Parameters: linel f3
Three·phase transmission line pi-section (mask) (link) . 1 hi-s block implement-s a lhtee·pha-se PI section line to represent a
three-phase transmis1on line. Thi-s block represents only one PI section.
To Implements more that one PI section. you simply need to connect
copies of this block in series.
Pt!lrameters ----------------------
Frequency used for A L C specification (Hz}:
50
Positive· and zero-sequence resistances (R1 (Ohms/km) RO
lr o.o1273 o.3B64J __ _
Positive· and zero-sequence inductances ( L 1(H/km) LO (H/km)):
jr 0.9337e-3 4.1264e·3J
Positive· end zero· sequence cepacitances ( C1 (F /km) CO(F /km)) :
I [12. 7 4e·9 7. 751 e·9]
Line section length [km) :
J5o
Cancel j I c:::::::ae.!i?.::·· .. ·:::u Apply
DEVELOPMENT OF~ UNDER FREQUENCY LOAD SHEDDING ALGORITHM
A
53
b) Load Model
r:1 untilled • 1!!1~ EJ [':1 ccc019/1 0 MW2 l!!llil £i
file f.dit ~ew ~imulation
Forma! T Qols
file .f,d1t Y:iew ~imulation Forma! Tgol$
D ~ lill «t l J(. ~ ~ 1 D Cii: liil ~
l-wr-\~1 P~r~\1 11\ RLC Lo~d 1
10 MW2
P•r•ll ll l RLC Load 2
1100~
Parall•l RLC Lo ad 3
I 100~
Dialog box for Load model
Block Parameters: 83 MW M\113 13 3-phase parallel RLC load (mask) (link) •
This block implements a three-phase parallel RLC load connected in Y configureation. with the neutral connected to the grcwnd. Each phase consist of one parallel RLC load block connected between the phase input and the ground.
Parameters----Nominal phase-phase voltage (Vrms):
~ Nominal frequency (Hz):
50
Three-phase active power P (W]:
fa3e6 Three-phase inductive reactive power Ql [var)
0
Three-phase capacitive reacive power Qc (var) :
0
OK Cancel Help ~PI=
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING ALGORITHM
.....,
A
54 ~ ~~~il
c) Transformer Model
~untitled '" BI!J Ef l:]Link: untilled/210MVA 13.8kV ... 1!!!1~13
file fdtt Y~ew ~imulation Forma!
T.Qols
file fdit l!iew ~IITlUiahon Forma.! T .Qols
li D
A2 I ' ' llr<P TI'----I 811> As2 11
C1 C2
2 10MVA 13.8kV : 230kV transformer ~ I .. J II
T2
= 1 [100~ .a C1
.__________.,~ ~
Dialog box for Transformer model ....
Block. Parameters: lOOOMVA 13. 8k.V : 220k.V transformer 13 Delta I Y linear tranformer (mask) (link)---
Thts block implements a three-phase linear transformer by using three mono-phase finear transformers. Winding one is connected in Delta configuration. Winding two is connected in Y configuration with neutral connected to the ground.
Parameters-- -(Three-phase rated power(VA) Frequency (Hz))
JIIIIIIJI@iiilll
Winding 1 (Delta)· (Ph-Ph Voltage(Vrms) R(pu) X(pu)]:
(1 13.8e3 0.0027 0.08) __ _
Winding 2 (Yg) (Ph-Ph voltage(Vrms) A(pu) X(pu)]:
J [ 220e3 0. 0027 0. 08]
Magnetizing branch: [Rm(pu) Xm(pu]):
J I 500 500 J
OK Cancel .!:!elp
DEVElOPMENT OF N1 UNDER FREQUENCY LOAD SHEDDING ALGORITHM
"::"
ode ,a
55
d) Generator Model
This block implements a 3-phase synchronous machine modeled in the dq
rotor reference frame. Stator windings are connected in wye to an internal
neutral point.
f:l unhtle d • 111!1~ EJ f ile ~dit ~iew .S.Jm!.Jetion Form.& T Qalr
D ~ liiil a . ~ ~ e Ji !2 ·~
I ~o;
mJu_SI
Synchronous M •ch ln e 1
I 100% l A]
Dialog box for Generator model
Bloc k P arame t e rs : S ync hronous Machine l 13 Synchronous Machine (m<!!tk) (link)
Implements a 3-phese synchronous m<!!chine modell~d in the dq rotor reference frame. Stator windings are connected in w.ve to an internal neutral point Press help for inputs <l!lnd outputs descnption
Parameters---Nom. power. L·L volt and freq. [ Pn(VA) Vn(Vrms) ln(Hz) ):
:300E t· 1 :::::00 ')(I
Reactences [ Xd Xd' Xd" Xq Xq" XI) (pu);
fr 1.3o5. o .296. o.252. o.474. o.243. o .18 1
Time constants [ Td' Td" Tqo"] (s)
Jr, .m . o.o53. o., 1
Stator resistance Rs(pu):
J2.8544e-3
Coeff. of inertia. friction factor and pe1rs of poles [ H(s) F(pu) p() ):
lr 3.2 o 321
lnit. cond. ( dw(%) th(deg) ie.ib.ic(pu) phe.phb.phc(deg) Vf[pu) ]:
Jro -74.1899 o .604649 o.6D4649 o.6D4649 -1.929 -121 .929 11 e.
r Simulate saturation
S<!!turetion perl!lmeters [ ild1 .ifd2 •. . (p u) ; vt1 .vt2 •.. . (p.u.) ]:
J [D. 64D4 .D. 71 27 .D. 8441 .0 . 921 4 .D 9956 .1 082.1 . 1 9.1 . 31 6.1 . 457 ;D
r::- Display Vfd which produces nom1nal Vt
OK Cancel tlelp
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING ALGORITHM 56 00
The first line of this dialog box is where you specify the nominal parameters: • Total three-phase apparent power Pn, in VA
• RMS line-to-line voltage Vn, in Vrms
• Electrical frequency fn, in Hz
Machine's reactance are specified on the second line (all in pu):
• d axis synchronous reactance Xd
• d axis transient reactance Xd'
• d axis sub transient reactance Xd"
• q axis synchronous reactance Xq
• q axis sub transient reactance Xq" I
• Leakage reactance XI
The third line contains the machine's time constants (all ins):
• d axis transient short-circuit time constant Td'
• d axis sub transient short-circuit time constant Td"
• q axis sub transient open-circuit time constant Tqo"
The fourth line is where you enter the stator resistance Rs, in pu and the fifth
line contains the mechanical parameters, but expressed in pu.
Inertia constant H, in seconds, where H is the ratio of energy stored in the
rotor at nominal speed over the nor;'inal power of the machine. Viscous
friction coefficient F, in pu, and Number of pairs of poles p.
The sixth line contains the initial conditions, and the initial line currents and
field voltage are expressed in pu , and the last line is where you specify the
Saturation parameters.
The parameters must be entered in per unit using the nominal field current,
multiplied by the d axis mutual inductance, and nominal rms line-to-line
voltage as base values for the field current, and terminal voltage, respectively.
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING ALGORITHM 57
Inputs and Outputs
The first input is the mechanical power at the machine's shaft. In the
generating mode, this input can be a positive constant or function or the
output of a prime mover block (see the Hydraulic Turbine and Governor
block}. In the motoring mode, this input is usually a negative constant or
function.
The second input of the block is the field voltage, which can be supplied by a
voltage regulator in the generating mode and is usually a constant in the
motoring mode. I
The first three outputs are the electrical terminals of the stator. The last output
of the block is a vector containing 16 variables. They are, in order:
1-3: Stator currents (flowing out of machine) isa, isb and isc
4-5: q and daxis stator currents (flowing out of machine) iq, id
6-8: Field and damper winding currents (flowing into machine) ifd, ikq and
ikd
9-1 0: q and d axis mutual fluxes
11-12:q and d axis stator voltages vq,vd
13: Rotor electrical angle
14: Rotor speed
15: Electrical power Pe
16: Rotor speed deviation dw
e) Hydraulic Turbine and Governor
...
The Hydraulic Turbine and Governor implement a hydraulic turbine model, a
PID governor system, and a servomotor. The static gain of the governor is
equal to the inverse of the permanent droop Rp in the feedback loop. The
input to this feedback loop can be selected to be the gate position or the
electrical power deviation by setting the droop reference parameter in the
dialog box to one or zero, respectively.
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING ALGORITHM 58 f7l 1~1
5 ~--------------------~
Pe
The hydraulic turbine is modeled by a nonlinear system with a water starting
time Tw.
/
beta
The PID regulator has a proportional gain Kp, an integral gain Ki and a
derivative gain Kd. The high frequency gain of the PID is limited by a first-.. order low-pass filter with time constant Td.
The gate servomotor is modeled by a second-order system with gain Ka and
time constant Ta. The gate's opening fs limited between gmin and gmax and
its speed is limited between vgmin and vgmax.
The last entry of the dialog box is used to specify the initial output power. This
value, which is used to initialize all the states of the model, allows you to start
the simulation in steady state.
0 regulator '3
output
servomotor
~ ~ ~peed po~ition limit limit
·rn ·~ ·rn 1 ·CD gate opening
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING ALGORITHM 59 Ubml
£ ~1---1111 ~~-=
Dialog Box
· Block Parameters: HTG
- Hydraulic Turbine and Governor (rrask) (link) -
lrrplerrents a hydraulic turbine corrbined to a PID governor system.
1st input desired speed (p.u.);
2nd input des1red rrechanic:al power (p.u.);
.3rd input synchronous rrachine's actual speed (p.u., rreasurerrent
; oulput 14 of SM block); 1
: 4th input: synchronous rrachine's actual electrical power (p.u.,
rreasurerrent oulput 15 of SM block);
5th input synchronous rrachine's actual speed deviation with
respect to nominal (p.u., rreasurerrent oulput 16 of SM block),
1stou1put: rrechanical power to be applied to the Synchronous Machine
block's 1st input (p.u.);
2nd oulput: gate opening (p u .).
r Para rrete m
Servo-rrotor [ KaQ Ta(sec) ):
I' I 1! 1 Of3 0.07]
Ga:te opentng limits [gmin,grrax(pu) vgmin,vgmax(puAs) ]:
[ 0.01 o.g7518 -0.1 0.1 ]
Perrranent droop and regulator [ ApQ KpQ KiQ KdQ Td(s) ):
lr 0 .05 1 .163 0.105 0 0.01 )
I Hydraulic turbine (betaQ Tw(sec) ):
' lr 0 2.67 ] -
Droop reference (O...powererror, 1..gate opening):
Ia ! I Initial power (pu) :
....
L@£ __ _ ·~ OK J l Cancel J L _Hel~ .t. ··;r• l· .• J
-~ ~· ,"'
~
J
I
J
J
I
l
I"
~
Inputs and Outputs
The first two inputs are the desired speed and mechanical power. The third
and fourth inputs are the machine's actual speed and electrical power. The
fifth input is the speed deviation. Inputs 2 and 4 can be left unconnected if you
want to use the gate position as input to the feedback loop instead of the
power deviation. All inputs are in pu. The outputs of the block are mechanical
power Pm for the Synchronous Machine block and gate opening (both in pu).
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING ALGORITHM 60
f) Excitation System
This model provides an excitation system for the synchronous machine and
regulates its terminal voltage in generating mode.
The basic elements that form the Excitation System block are the voltage
regulator and the exciter. The voltage regulator consists of a main regulator
with gain Ka and time constant Ta and a lead-lag compensator with time
constants Tb and T c. A derivate feedback is also provided with gain Kf and
time constant Tf. The limits Efmin and Efmax are imposed to the output of the
voltage regulator. The upper limit can be constant and eq~al to Efmax or .
variable and equal to the rectified stator terminal v_9Jtage Vtf times a
proportional gain Kp. If Kp is set to zero, the former will apply. If Kp is set to a
positive value, the latter will apply. The stator terminal voltage transducer is
represented by a first-order low-pass filter with time constant Tr.
vref
vo!Jb
oq1(u(l )"2. 11(2)"2)
Poorllw 5eqora IA:>Itoge
Dlml>ng kf.tl(lf_. •I)
The exciter is represented by the following transfer function between the
exciter voltage Vfd and the regulator's output ef:
vfd - 1 ef - Ke + sTe + S(Vfd)
Where S(Vfd) is a nonlinear function that represents the magnetic saturation
of the exciter. This saturation function is given by:
S(Vfd) = AeBVfd
The last entry of the dialog box is used to specify the initial values of the
terminal voltage and field voltage. The values used to initialize all states of the
model allow you to start the simulation in steady state.
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING ALGORITHM 61 f7l l~d~
Dialog Box
I
Block Parameters: EMcitatio n System
Excitation System (JTBsk) (link) ----------..,.,---------.
II'T'plements an IEEE type 1 synchronous JTBchine voltage regulator corrbined to an exciter. This block uses the dq COI'T'ponents of terminal
voltage (Synchronous Machine block, measurement ouputs 9 and 1 0) .
1st 1nput: desired stator terminal vol1age (p .u.); 2nd input: vd COI'T'pOnent of the terminal voltage (p.u.); 3rd input vq COI'T'ponentofthe terminal voltage (p.u.); 4th input: stabilization voltage from user-<Supplied
power e:oystemstabilizer (p.u.);
output. field voltage vfd to be applied to the _ Synchronous Machine block's 2nd input (p.u.).
Parameters - ---
Low-pass filter time constant Tr(s): --------~~----------------------~--~ 20e - 3
Regulator gain and time constant [ KaQ Ta(s) ]: - -- --~~--------------------~~ [ 300, 0 .001 ]
Exc1ter [ KeO Te(s) ]:
[ 1 , 0]
Transient gain reduction [ Tb(s) Tc(s) ]:
[ 0, 0]
Dai'T'plng fii1Br gain and time constant [ KfQ Tf(s) ] ·
[ 0 0 0 1 , 0 .1 ]
Field saturation pararre1Brs [A, 8 ]:
[ 0, 0]
Regulator output limits and gain [ Efmin, EfJTBx (p.u.), KpQ ]: ....;_,;...__ __________ ..., [ -1 1 .5 , 11 .5 , 0 ]
ln1t1al values of terminal voltage and field voltage [ VtO (pu) VfO(pu)] :
-[1 .0 1 .28]
OK Cancel Help-. -J -. -~·.p i:-.- - ~ ~
Inputs and Outputs
The first input of the block is the desired value of the stator terminal voltage.
The following two inputs are the vq and vd components of the terminal
voltage. The fourth input can be used to provide additional stabilization of
power system oscillations. All inputs are in pu. The output of the block is the
field voltage Vf for the Synchronous Machine block (p.u).
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING AlGORITHM 62
g) Generator and Transformer Sub System
l:] G en_ T r ansmdl !I Iii f.3 file ~dit ~iew ,S.imulation Forma! T .Qols
o I ~ Piil ~ I ~ ~. ~ 1: .!2 c 1= ~ •
I Library Browsed
Pill tfrLA A1 1\Z
\WL,' r---+--..---~ ·~t> k2 " I .. ,V't C :
I ~MHJ lutJid
111 14-------------' Y-----t---1Pe
5pttd¢lC)
dw
su Utau~tmut Dtmu
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING ALGORITHM
...
< • () I IS UI/U
ode45 M
63 [iJ
9.3. APPENDIX 3 ; Actual Frequency variations
i 1 & I
!
·20
02
01
.01
c. .02
g .03
.QC
.OS
-06 -20
·10
I"
~ ~ ~1
-tO
502
50
498
Frequency Gra ph for 97 MW Generotion loss
10 20
Time (o)
System dfldt vs Time Graph for 97 MW Generation loss ....
N1 11. ~ r11 I 1JI 1 lllll MBfl
l. ~JlW 1\IIIU ...u
ff1 ' I 1l rn\' Jlj¥1 .
I
I I
tO 20
Tlme(o)
DEVELOPMENT OF AN UNDER FREQUENCY lOAD SHEDDING AlGORITHM
;I
30 40
.L
I plY f ~ ~~ ,.,
""( Ulll
~..,. (Y> ~~xrs Major Grichi 1
30 40
50
50
64 ~ ~~1.
Frequency Y5. Time Gnaph for 16G MW Gene radon Lou
N
~
l ...
I I I TTT '-~ f\ I 11 T r ', I ~~~~~~ "-"- Jj T1ITIJ I . \ r- ~~ FFF~
I \ I ,__._.,_
~ I i \ I I I I lA I, / 1 I I t~ \~ IY 'IT T II t--
-- ~~--- • I \ 1/ IT I I
lJ I 1 JI -~- Vj 1 ll il . .J l ll [I Jil1 --1 ;,C:Q -Jj__ _Jj JJJ J 11
·4 ·2 Plot Ar"o.. I 10 12 14
Time (1)
dffdt v• time Gnaph for 16G MW Generlltion lou
06
04 ~. fllnru, 11{')1 I V II"
02 V\ "-"tf""l 'h
IIV tl/1 111
I\ I v
~ 0 JVV~I'\ r•
~
~ · 0 2 r
·0 4 uJ' n;u
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· 4 ·2 10 12 14
Time (1)
DEVELOPMENT OF AN UNDER FREQUENCY LOAD SHEDDING ALGORITHM 65