Table Of ContentEnergy Systems in Electrical Engineering
Kabir Chakraborty
Abhijit Chakrabarti
Soft Computing
Techniques
in Voltage
Security
Analysis
Energy Systems in Electrical Engineering
Series editor
Muhammad H. Rashid, Pensacola, USA
More information about this series at http://www.springer.com/series/13509
Kabir Chakraborty · Abhijit Chakrabarti
Soft Computing Techniques
in Voltage Security Analysis
1 3
Kabir Chakraborty Abhijit Chakrabarti
Electrical Engineering Department Electrical Engineering Department
Tripura Institute of Technology Indian Institute of Engineering Science
Agartala and Technology, Shibpur
Tripura Howrah
India West Bengal
India
ISSN 2199-8582 ISSN 2199-8590 (electronic)
Energy Systems in Electrical Engineering
ISBN 978-81-322-2306-1 ISBN 978-81-322-2307-8 (eBook)
DOI 10.1007/978-81-322-2307-8
Library of Congress Control Number: 2015932428
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Dedicated to
My Parents
Mr. Kalyan Chakraborty
and
Mrs. Anjali Bhattacharjee
—Dr. Kabir Chakraborty
Preface
Voltage security is recognized as a key issue for power systems operation. The con-
tinuous increase in loads, along with economic and environmental constraints, has
led the systems to operate close to their limits, and this includes voltage security
limits. Academicians as well as practicing engineers are switching over to stud-
ies of the numerous problems associated with the planning and operation of large
interconnected power systems. Courses in power system analysis are being updated
to reflect the importance of new tools such as computer, control, and systems
theory. During the last 30 years, several papers and conference reports on power
system voltage security have been published throughout the world, indicating the
continuing interest of electrical engineers in this field. During these years, this sub-
branch of electrical engineering has also come in quite close contact with a number
of related disciplines such as optimal control theory, digital techniques, etc.
To maintain power systems security, it is essential to keep the operation within
a specified margin of real and reactive power flow and this is usually mandated
by the local reliability organizations. These margins are calculated from offline
studies, thus it takes a good amount of time to figure out such margin points. The
human operators in the control centers then utilize these conservatively tabulated
values for secure power system operation. In this book, different approaches to
improve such operational procedures are highlighted.
Remarkable advances in research in the field of power system security analysis
for the computation of power system security margins have been noticed in the
last 30 years. In the meantime, the extraordinary development in computational
rates of recent computers has brought online security study closer to realistic utili-
zation. In recent days, to satisfy the increasing power demands of consumers, the
power system operating conditions are changed in an irregular fashion. For that, it
is necessary to recompute the system security margins precisely to confirm secure
operation of the systems, which is computationally infeasible. Presently, the use
of soft computing techniques in voltage security study has picked up because of
its capacity to do parallel data handling with high precision and quick response
times. “Soft computing”, rather than routine “hard computing”, is a procedure
that is tolerant of indecision, imprecision, incomplete truth, and rough guesses.
vii
viii Preface
The soft computing techniques are modeled on the concept of the human brain,
for which these are termed as Artificial Intelligence. These methods are fit for
arriving at substantial conclusions based on deficient and fractional information
obtained from prior knowledge just like in the human brain. Soft computing pro-
cesses use an approximation of this concept on a very small scale. It is economical
and consumes less time. Different branches of soft computing techniques are now
available; among them three major branches are genetic algorithms, artificial neu-
ral networks, and fuzzy logic. In this book, Artificial Neural Network (ANN) has
been chosen as a soft computing tool, since, such networks are eminently suitable
for the study of voltage security. The different architectures of the ANNs used in
this book are selected on the basis of the intelligent criteria rather than by a “brute
force” method of trial and error with different architectures.
The fundamental aim of this book is to present a comprehensive treatise in
order to study the power system security and simulation of power system security
studies. The topics are substantiated by suitable illustrations and computer
methods and describe analytical aspects of operation and characteristics of power
system from the viewpoint of voltage security.
The number of books dealing only with the problem of power system security
is, rather low, especially in consideration of the rapid growth of this topic in recent
years. Most of the advanced books devote only a chapter to the topic of power
system security/stability. However, the versatile concepts used in different aspects
of security need a much more thorough discussion. This fact stimulated us to make
an effort to prepare a book that would cover fairly the concepts and problems of
power system security. Besides that, in this book a number of MATLAB programs
related to voltage stability/security are provided and some basic chapters like load
flow analysis are also included.
The text is self-contained and thorough. It is intended for senior undergraduate
students and postgraduate students in Electrical Engineering. Practicing engineers,
Electrical Control Center (ECC) operators and researchers will also find the book
suitable for their use.
Any constructive criticism and suggestion in improving the book further will be
highly appreciated.
January 2015 Kabir Chakraborty
Abhijit Chakrabarti
Acknowledgments
The authors are pleased to acknowledge the assistance given by a number of
people including their students. Special acknowledgment is due to Dr. Abhinandan
De, a faculty in Department of Electrical Engineering, Indian Institute of
Engineering, Science and Technology, Shibpur, for his technical support. The
authors acknowledge the help rendered by Dr. Dipanjana Chakraborty in checking
the proof of the entire text. Kabir Chakraborty appreciates the patience and sup-
port of his parents and child (Karnak) during the long period devoted in preparing
the book. The support and encouragement of Swati Meherishi, Publishing Editor
and Aparajita Singh, Editorial Assistant of Springer is also acknowledged.
January 2015 Kabir Chakraborty
Abhijit Chakrabarti
ix
Contents
1 Voltage Security—An Introduction ............................. 1
1.1 Introduction ............................................ 1
1.2 Basic Components of Power System ......................... 1
1.3 Threats to Power System Security ........................... 4
1.4 Reasons for Power System Blackout ......................... 5
1.5 Necessity for Voltage Security Analysis ....................... 6
1.6 Application of Soft Computing Techniques
in Voltage Security Assessment ............................. 7
References .................................................. 10
2 Load Flow Studies ........................................... 11
2.1 Introduction ............................................ 11
2.2 Formation of Admittance Matrix [Y ] ....................... 12
Bus
2.2.1 [Y ] of a π-Equivalent Model of a 2-Bus System ........ 14
Bus
2.2.2 Formation of [Z ] from [Y ] ....................... 15
Bus Bus
2.2.3 MATLAB Programs for Formation of Y .............. 17
Bus
2.2.4 Modification of Y Due to Presence
Bus
of Transformer in the Line ........................... 21
2.2.5 MATLAB Program for Formation of Modified Y ....... 24
Bus
2.3 Power Flow Solutions ..................................... 27
2.3.1 Classification of Bus ................................ 28
2.3.2 Power Flow Equations .............................. 30
2.4 Gauss-Seidel (G–S) Method of Power Flow ................... 33
2.5 Newton–Raphson Method of Power Flow ..................... 35
2.6 Fast Decoupled Method of Power Flow ....................... 48
2.7 Line Power Flow ........................................ 53
References .................................................. 57
xi
