In this project, the load and frequency control problem on the power generator at 'Britannia sugar factory' is investigated under different governor action. The existing system employs a Mechanical-hydraulic governor. It is desired to improve the system's response to load disturbances on the interconnected power grid.

1. [-(}Am & FREqiENC]r CGNTR#H- STliiimY,&,lr
iB lRn n- A. Tq N X A tr [-A Nif Lii ].{lD IE R lD lt F IF E RIE NT
CiCI/ E]RNC}R_ "ECT ]t CI NS
PgTvin BEEKHARRY
PROJECT SLIBN,{ITTED ii.] PARTJ.iL
REQLTTRF'h..IE;rT FOR A 'B.TECH (HONS)' tTEGREE llr
ELI]CTRICAL ANID ELECTRO]'JIC ENIGIJ{EER}1{G
Department of trlectrical and Electronic
Faculf ,v oi Engineering
TTTI IVERSITY OF N,IALIRITIUS
lv{arelr 1996
€ffi'@v

2. DEDTC&TED TS
MY BE-toVE-D P&&ENTs
L*

3. My tlianks goes ta all those who have s*pported me duri,g this project.
I am Very grateful to the personnel of 'Britannia' sugar iactor},. its oniy,
with their help. that most of the practical rvork has been possible.
I express mv thanks to Mr.C Bhufiun, for his guidance and critical viervs
on the project.

4. In this project. tire Loaci and Frequency control pro"bierrl o11 tire generator
at 'Britannia' silgar tactory, is investigated under ditlbrent gor€rilor
actions. The cxrstinu s-vstem emplol-s a Meehanical-hvdraulic governor. It
is desired to improve the systern's rospollse to toad disfurbances. in this
prospect. the perti-.rmance of the generator is analvsed. under tlour
different govemor modeis nameiy ;
1. Mechanical-hydraulic governor. model i
2. Mechanicai-hrvdrauiic governor r"vith speed rela1,. mociei II
-3. Electro-hvdraulic governor. model III
1. Hl,dro gol'ernor. model IV
The system pertbrmance is greath' improved uith Eiectro-hydraulic
ccntrol.

5. 1. INTRODLTCTION
1.1
1.2
1.3
1Ar .'t
i.5
1A
a-
t.t
Electric Energv
E lectric Energ-v cr:n',,ersir-rn
Megar."att-Frequenci ( P-l) interaction
1 .3.1 Impofianee of eonstart tiequenel'
hllegavar-Voitage (Q-V ) interaction
1..+.1 Cross cciupling betr-r,,een P-f and Q-V ei-rntrol lo.--rps
Geterator controi scireme
r i r 't L^ A /t, t_- --t.J.r t Iltr flvr tLrrrF,
1 .5.2 The ALFC loop
Pooi operation
Project outiine
2. POWE.R SYSTEM COMPONE},ITS
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T,^r--^ l-- ^rl ^,-tIIIrrilttta"tltlrI
Gol,errtor
2.2.1 hlain tbatures of a speed governing s_r'stein
2.2.2 Speed gol'eruing svsterns
2 -2.3 Governor characteristics
Prime movcr
2.3.1 Steam tur'oines
A l+^^-* ^+^--,.nlttiM,iltLrI )
Oil srrsterns and Lubrification
,L"J
2.4
2.5
MT}L]EL DETELOPMENT
3.1 Introduction
3- 1 .1 Mathematical mr:del
3.1.2 State spaoe model
3.2 Elements of speed governing systems
3.2.1 The flyball governor
3.2.2 The servomotrr
3"2.3 The Speed relay
3.2.4 Dashpot
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6. Goverror models
3.3. 1 }vieciranicai-hycirauiic gor,ernor tirr stealn turbines
3.3.2 Electro-hvdraulic go-r,eftior tbr steam turbines
.i.-j.-3 Mechanical-hrdraulic govenror fiii' Hrdr,i tui'biiics
Turbine modeliing
1 t I (.--,-- ---,-r-'
-i.-{. i Slea'rii ttii Dities
Generator load mo,Jel
Colnplete block diaqrarrr arrd State space representation of
an isolatcd Por.r:er svstern under different gor/ernor aetions
3.6.1 Meciranicai-hi'drauiic govemor, generator modei i
3 .6 .2 Mechanical-1i-.,drarilic governcrr r,r,ith Speed relai'.
generator modei Ii
3.6.3 Elecirri-hr',irai.iiic Et-ri'e fficrr. seirerator nrociei III
? ( J Efr lrr- o,'prrr.r oenprelrrr rrrrrrlol I./-j !Lr. I .
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T-^+--- l-, ^+i ----I t r I I I tI I I ta;t ta It I
Steacit' state analysis
E - i ('r^+i^
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Freque:rc*. dornain
Bode piot approacir
5.4.1 Peritrrrnanee evaination tiorn Bode piot
Dnnt l^^rro ^^^*^^^Lr.LrLrt rl.rvLlJ Clyyr wilrrlI
5.-5. 1 Mcehanieal h-",clraulic govcrnor- generator mr-rdel
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4. i introciuction
4.2 Plant lavout
J ) 1 l-)r'nrrrttrr'rits"-v*'
4.:J The intinite bus
4.3.1 S1'nehronisation
4.+ Monitorirle and Protectiorr
:1.5 Load ehaiaetcristics
4.5. i Voitage and frequera]' ioad ciepenciencl'
4.6 Experimental deterniinaticn of parameters ti;r Britannia plant
4.6.1 Deterinination of 'B'
4.6.2 Calcuiation of I)roop tbctt-rr 'R'
tL)T*l----l
+.u.-'! rtLtII-uu ll tssr
5. SIMULATION RESULTS : AIIALYSIS IN THE S-PLANE
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5.2

7. 5.5.2 Elcetro-hldraulie goreruor- genei'ator model III
5.5.3 Hydro mociei IV
{; SIMIJLATION RE,S-I.JLTS : STATE SPACE A}{ALYSIS
(ntta
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6.4
T^t.^lrrnfi,--IIT II VU L}V I1UIT
State space Approach
6.2.i Meehanieai h1'draulie gr-rvemor. generator mcrdei i
i, 1 ^t R/t^^L^..:^^1 1.,-1..^,,1:^ ^^.,^-.-^-,,,i+L .,^^^l -^1 ^..r./..L lvlLLlldlllLdl ll-Llleltllllv U,LrrUlIlLrI lttll JlrtvLJ lt/ld.
generator ir,,-idel II
6.2.3 Eiectro-hvdraulic goverrlor. generator model III
6.2.4 H1'dro governor. geflerator iriodel IV
Time rssponse
Perlbrrrrarrce Er aiualion
1
C {-)N'-] T .i-I:] I (-N S & RE. {] OMMENDATION S
Conclitsit-:ns
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DEF.INITION FOR h4L}DEL S YI-,,IBOLS
APPE}TDIX A
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8. Chopter
INTRODUCTION
1.1 Electric Energy.
Electric energy is an essential ingredient for the industrial and all-round
development of any country. In fact it has become so important, that the per
capita consumption of electrical enerry is taken as a reliable indicator of a
counfiy's state of development on the same ground as the Gross Domestic
Product.
It is a coveted form of energy, because it can be generated centrally in bulk
and transmiued economically over long distances. Further, it can be adapted
easily and efficiently to domestic and industrial applications, particularly for
lighting purposes and mechanical work, e.g. drives.
It is also considered as a clean source ofenergy.
1.2 Electric Energy Conversion.
Although the direct conversion to electric energy from other energy forms
such as Solar and Magnetohydrodynamic O/ffD) are being developed, the
prime energy sources of elecfric enerry generation are still Fossil fuels,
Hydropower and Nuclear energy, and to a much lesser extent, Tide and
Wind.
The energies are already in the form of mechanical energy as in the case of
Hydropower, Tide and Wind or must first be converted into mechanical
energy through steam turbines before the final process of Mechanical-
Electrical enerry conversion, as with Fossil fuels and Fission material.
Therefore, the important components basic to an electric power plant are the
Hydro and Steam turbines, the Electric generator, the Governor to control the
energy input to the turbines, and the Exciter voltage regulator confrol of the
electric output of the generator.
The major portion of the generated electric energy is transmitted to load
centers through transmission lines, although some electric energy must be
used for local supply, and some losses always occur in the generation and
transmission proce sses.
*

9. 1.3 Megawatt-Frequency ( P-f ) interaction
The frequency of a system is closely related to the real power balance in the
overall network. The real power is confrolled by varying the driving torques
of the individual turbines of the system.
Let us consider what would happen if a generator running at 50 Hz perfectly
power matched, experiences a small load drop.
Initially, the prime mover valve setting would be unchanged, i.e. the driving
torques are unchanged. The decrease in load results in a current decrease in
the network, resulting in a slight decrease in the electromechanical torques in
the machine. The generator will experience a small surplus accelerating
torque, with an ensuing speed and frequency increase. The rate at which the
speed 'CI' increases, depends upon the moment of inertia of the running
machine. This can be shown from the swing equation .
T2
'Tl' is the driving torque and'T2' the load torque.
Let the moment of inertia of the combined system be 'J'.
Applyrng Newton's law :
Tl -T2 : d(Jro)
dt
Tl-T2: J d(ro)
dt
1.3.1 Importance of constant trequency fll
The reasons for keeping strict limits on the system frequency fluctuations are
as follows :
l. Most types of ac motors run at speeds that are direcfly related to the
frequency.
2. L large number of electrically operated clocks use slmchronous motors,
and the accuracy of these clocks is a firnction of the integral of frequency
erTor.
3. The overall operation of a power system can be muoh better confrolled if
we keep the frequency error within strict limits.
4. Timing circuits in certain elecfronic apparatus use system frequency as a
reference.
T1
Figure 1.1

10. 5. A changrng system frequency is the index of mismatch between total
system generation and total load.

11. 1.4 Megavar-voltage ( Q-V ) interacfion [1]
Practically all equipment used in or operating off a power system is designed
for a certain voltage level. If the system voltage should deviate from that
value, the perfofinance of the device suffers. In order to confrol the voltage
level , we have to keep a balance between produced and consumed reactive
power.
To understand this situation, consider the two-bus system in figure 1.2 . The
load ( P + jQ ) is tapped from load bus 2. Since no generator exists at this
bus, power must be transmitted along the line.
P+JQ
Figure 1.2
J We make the following assumptions.
1. The bus voltage Vl is kept at constant magnitude by field confrol of Gl,
we choose Vl as our reference voltage.
2. The transmission line impedance is purely inductive , i.e.
Z: jx
Due to voltage drop along the line, we have the following voltage relation :
Y2 = Yl -IZ
The line current I satisfies the relationship
Vl I* sP+jQ
TX P+JQ: P.JQ
TTT TT-
Substituting in 1-l
(1 -1)
xQ - jx P
mmV2: Vl- P-jQ ljx : vr.=rl

12. From the phasor diagram we conclude
o A change in real load P affects the voltage drop phasor which is
perpendicular to Vl. No appreciable change in magnitude V2 will thus
ensue.
. A change in the reactive power Q affects the voltage drop phasor which is
in phase with Vl. The change in the magnitude is therefore essentially
proportional to Q
1.4.1 Cross-coupling between P-f and Q-V control channels. |l
For small deviations, there is little interaction between Pf and QV control
loops.
In general, the QV loop is much faster than the Pf loop, due to the
mechanical inertia constants in the latter. If it can be assumed that the
fransients in the QV loop are essentially over before the Pf loop reacts, then
the coupling between loops can be neglected.
1.5 Generator control scheme
Generators control their Real power and Reactive power generation through
two major control loopd.
1. The Automatic Voltage Regulator ( AVR ) loop
2. The Automatic Load Frequency Control ( ALFC ) loop
Figure 1.3 depicts the various conhol loops of a synchronous generator.
1.5.1 The AVR loop
The AVR loop controls the magnitude of the terminal voltage V. The latter
voltage is continuously sensed, rectified and smoothed. This dc signal, being
proportional to V , is compared with a dc reference, Vref. . The resulting
'error voltage', after amplification and signal shaping, serves as input to the
exciter, which finally delivers the voltage Vrto the generator field *inding.
1.5.2 The ALFC loop
The .ALFC loop regulates the Megawatt ou@ut and frequency of the
generator. The loop consists of :
. A relatively fast Primary loop, which responds to a frequency signal from
the speed governor and via the control valves, regulates the flow of steam
with the intent of matching the Megawatt output to Load fluctuations. The
primary loop prevents the frequency from deviating by a large amount, but
does not bring it to the prescribed value of 50 Hz.

13. A slower secondary loop maintains the fine adjustnents of the frequency.
This loop is insensitive to rapid load and frequency changes, but focuses
on drift like changes which takes place over periods of minutes.
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14. 1.6 Pool operation
From a practical point of view, the problems of load frequency control of
interconnected areas or 'power pools', are more important than those of
isolated areas. Most power systems, normally control their generators in
unison. The individual confol loops must have a coflImon parameter which is
the Droop gain. It is also desirable that the individual generators have the
same response characteristics, then it is possible to represent the whole
system by a single confrol loop, which would be referred to as a Confrol
area. This finds its importance in large power system studies. Generators
working in parallel on the same network ought to have the same Droop ( per
unit ) in order to share load changes in proportion to size.[]
The advantages derived from pool operation are :
1. Better regulating characteristics, since a load change in any of the systems
is taken care of by all units in the interconnection.
2. During emergency conditions, the power pool can continue to operate. If a
unit is lost, governing actions from all interconnected areas will increase
generator outputs to make up the deficit until stand-by units can be
brought on line.
3. Better economics of operation.
During pool operation, each pool member must follow certain principles.[1]
. Under normal operation, each pool member should strive to carry its own
load, except during load sharing.
. Each confrol area must agree upon adopting regulating and control
strategies .
. System frequency must be kept as far as possible at its nominal value of
50 Hz.
1.7 Project Outline
The project is outlined as follows :
. In chapter two, we infroduce the main power system components involved
in Load and Frequency confrol.
. Chapter three deals with modeling the system using mathematical tools.
o In chapter four, we familiarae with the 'Britannia' plant itself and study
the experimental determination of model parameters.

15. . In chapter five, we study the system's stability in the frequency domain
and compare the merits of the different models.
o Chapter six presents the results of computer simulations in the time
domain.
. And finally in chapter seven, we present a conclusion and give certain
recoillmendations.
-