National Conference-NCPE-2k15, organized by KLE Society's Dr. M. S. Sheshgiri College of Engineering & Technology, Belagavi,
Special issue published by Multidisciplinary Journal of Research in Engineering and Technology, Pg.56-63
Journal homepage: www.mjret.in
ISSN:2348 - 6953
Modeling of Synchronous generator connected to
Infinite-Bus
Vijaykumar.S, Vijeta.B, Vishal.P, Jagadish.B, Javeed.Kittur
Department of Electrical and Electronics
B. V. B. College of Engineering and Technology
Hubli, India
biradarjaga@gmail.com, Vijaysalagare@gmail.com, Vijeta.bellubbi@gmail.com,
vishalp19195@gmail.com , and javedkittur89@gmail.com
Abstract: The behaviour of Synchronous generator (model 1.0 and model 1.1) connected to Infinite-Bus
when a disturbance occurs is considered. The disturbances considered are small signal and large signal.
The changes in the state parameters are analysed. The synchronous generator is represented by differential
equations. Therefore numerical methods are used for the solution; the method included here is Euler’s
method. The behaviour is analysed by writing code in C and C++ languages and plots are obtained using
GNU plot.
Keywords: Small signal disturbance, large signal disturbance and GNU.
1. INTRODUCTION
Power is generated by the synchronous generator. The generator has to operate with synchronism
with the rest of the system. A generator is said to be synchronised with the bus only when the frequency,
voltage and phase sequence of the incoming bus and that of the generator is same. Therefore, Power
system stability may be broadly defined as a property of a power system that enables it to remain in state of
operating equilibrium under normal operating condition and to regain its state of equilibrium after being
subjected to a disturbance. [6]
The objective of our project is to investigate the stability and changes in the state parameters of
Synchronous generator connected to Infinite-Bus when disturbances are occurred. Here small signal and
large signal disturbances are considered.
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National Conference-NCPE-2k15, organized by KLE Society's Dr. M. S. Sheshgiri College of Engineering & Technology, Belagavi,
Special issue published by Multidisciplinary Journal of Research in Engineering and Technology, Pg.56-63
2. MACHINE MODELS
Fig 1: synchronous machine
Insufficient damping in the generator causes spontaneous hunting, giving rise to stability problems.
To overcome this, generator damper windings were included.
The synchronous machine considered above has three phase armature windings (a, b and c) on stator
and four windings on the rotor including the field winding „f. The damper circuits in the salient pole machine
or the eddy current effects in the rotor are represented by a set of coils with constant parameters. Three
damper coils, „h in the d-axis and g, k on the q-axis. The number of damper coils represented can vary from
zero to many. [1]
Depending on the number of rotor windings, the number of state variables varies. Therefore, Models are
classified based on varying degrees of complexity.

Classical model (Model 0.0)

Field circuit only (Model 1.0)

Field circuit with one equivalent damper on q-axis (Model 1.1)

Field circuit with one equivalent damper on d-axis.
a)
Model 2.1 (one damper on q-axis)
b) Model 2.2 (two dampers on q-axis)

Field circuit with two equivalent damper circuits on d –axis.
a) Model 3.2 (with two dampers on q-axis)
b)
Model 3.3 (with three dampers on q-axis)
In classification of the machine models, the first number indicates the number of windings on the direct
axis while the second number indicates the number of windings on quadrature axis. Here model 1.0 and
model 1.1 are considered. [1]
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National Conference-NCPE-2k15, organized by KLE Society's Dr. M. S. Sheshgiri College of Engineering & Technology, Belagavi,
Special issue published by Multidisciplinary Journal of Research in Engineering and Technology, Pg.56-63
3. SYSTEM SIMULATION EQUATIONS

The load angle is the angular displacement of the generator's rotor from the no-load position
referred to as terminal voltage. It also indicates the amount of power that can be transferred .


Internal voltage of rotor (q-axis)

=
Internal voltage of rotor (d-axis).
Only present in machines consisting equivalent damper winding.

It provides the direct current to synchronous generator field winding.

The plots obtained for salient pole synchronous generator are shown below. Parameters of the system are,
xd=1.8,xq=1.7,xdd=0.17,xqd=0.23,xe=0.25,tdod=6,tqod=0.1,h=5,f=60.
From the power flow analysis
Pt=1.0,Eb=1.0,Vto=1.0
In order to calculate the state parameters, we make the following assumptions when analyzing the models.

Stator transience is neglected.

Line resistance is neglected.

Magnetic saturation is not considered.

Harmonics are neglected.
4. SMALL SIGNAL DISTURBANCE:
Small signal stability is the ability of the power system to maintain synchronism following small and
gradual disturbances. The system takes less time to become stable. This accounts for changes in the bus
58 | P a g e
National Conference-NCPE-2k15, organized by KLE Society's Dr. M. S. Sheshgiri College of Engineering & Technology, Belagavi,
Special issue published by Multidisciplinary Journal of Research in Engineering and Technology, Pg.56-63
voltages close to the nominal values. These are caused due to random fluctuations in loads and generation
level. In this case, the disturbance given is a 10% change in mechanical torque. The disturbance may also
be given as change in reference voltage value. The plots are obtained by writing code in C language for
Euler’s method to the system equations represented by differential equation. [2-4]
Fig 2: Variation of slip vs time for model 1.0
Fig 3: Variation of Rotor angle vs time for
model 1.0
Fig 4: Variation of Torque vs time for model
1.0
Fig 5: Variation of Excitation system voltage
vs time for model 1.0
Fig 6: Variation of slip vs time for model 1.1
Fig 7: Variation of Rotor angle vs time for
model 1.1
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National Conference-NCPE-2k15, organized by KLE Society's Dr. M. S. Sheshgiri College of Engineering & Technology, Belagavi,
Special issue published by Multidisciplinary Journal of Research in Engineering and Technology, Pg.56-63
Fig 8: Variation of Torque vs time for model 1.1
5. LARGE SIGNAL DISTURBANCE:
Fig 9: Variation of Excitation system voltage vs
time for model 1.1
This accounts for major disturbances. This may be due to sudden acceleration of the rotor
shaft. The system takes considerably much time to become stable. The large signal disturbance
considered is three phase fault and it is prevailing for two cycles. For time, at reference seconds,
the switch is connected to the incoming generator and thus the generator becomes isolated to the
grid connection as a result terminal voltage becomes zero. For the terminal voltage to be zero,
direct axis voltage and quadrature-axis voltage are reduced to zero. As a result, direct-axis current
and quadrature-axis currents are updated. Therefore, Code is written in C for Euler’s method for
various state variables. [2-4]
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National Conference-NCPE-2k15, organized by KLE Society's Dr. M. S. Sheshgiri College of Engineering & Technology, Belagavi,
Special issue published by Multidisciplinary Journal of Research in Engineering and Technology, Pg.56-63
Fig 12: Variation of Torque vs time for model 1.0
Fig 13: Variation of Excitation system voltage vs
time for model 1.0
Fig 13: Variation of Excitation system vs time
for model 1.0
Fig 14: Variation of slip vs time for model 1.1
Fig 15: Variation of Rotor angle vs time for
model 1.1
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National Conference-NCPE-2k15, organized by KLE Society's Dr. M. S. Sheshgiri College of Engineering & Technology, Belagavi,
Special issue published by Multidisciplinary Journal of Research in Engineering and Technology, Pg.56-63
Fig 16: Variation of Torque vs time for model 1.1
Fig 17: Variation of Excitation system voltage vs
time for model 1.1
6. CONCLUSIONS & FUTURE SCOPE:
The behaviour of the synchronous generator connected to infinite bus system, when faults occur is
realised. Which can be used in implementation of power system stability where change in load angle act as
input signal. Similarly, the increase in rotor speed can also act as an input to activate a mechanism to
maintain stability. This is of greater importance in multiple machine system.
REFERENCES
[1]K.R.Padiyar, “Power System Dynamics – Stability and Control”, second edition, BS Publications.
[2] S.S.Sastry, “Introductory Methods of Numerical Analysis”, fourth edition, PHI publications.
[3]Dr. E. Balaguruswamy,”Programming in ANSI C”, sixth edition, Tata Mc-Graw Hill Publications.
[4]Dr. E. Balaguruswamy,”Object Oriented Programming with C++”, fourth edition, Galgotia Publications.
[5] Venkatesh Gudla, P. Kanta Rao,”Improvement of Dynamic Stability of a single machine Infinite-Bus Power System
using Fuzzy
Logic based Power system stabilizer”.
[6] P. C. Sen, “Principles of Electric Machines and Power Electronics”, second edition, John Wiley& sons Publications.
LIST OF ACRONYMS
Rotor angle of synchronous generator in radians
Rotor speed deviation in rad/sec
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National Conference-NCPE-2k15, organized by KLE Society's Dr. M. S. Sheshgiri College of Engineering & Technology, Belagavi,
Special issue published by Multidisciplinary Journal of Research in Engineering and Technology, Pg.56-63
Generator slip in p.u.
Initial operating slip in p.u.
H
Inertia constant
D
Damping coefficient
Mechanical torque in p.u.
Electrical torque in p.u.
Excitation system voltage in p.u.
Open circuit d-axis time constant in sec
Open circuit q-axis time constant in sec
d- axis synchronous reactance in p.u.
d- axis transient reactance in p.u.
q-axis synchronous reactance in p.u.
q- Axis transient reactance in p.u.
Internal voltage of rotor (q-axis)
Internal voltage of rotor (d-axis)
q- Axis voltage
d- Axis voltage
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