AC Machine Systems: Mathematical Model and Parameters, Analysis, and System Performance

503 Pages·2009·4.82 MB·English

by  Jingde Gao, Linzheng Zhang, Xiangheng Wang

Jingde Gao
Linzheng Zhang
Xiangheng Wang
AC Machine Systems
Mathematical Model and Parameters, Analysis, and System
Performance
Jingde Gao
Linzheng Zhang
Xiangheng Wang
AC Machine Systems
Mathematical Model and Parameters, Analysis, and
System Performance
With 158 figures
Authors
Jingde Gao Linzheng Zhang
Dept. of Electrical Engineering Dept. of Electrical Engineering
Tsinghua University Tsinghua University
100084, Beijing, China 100084, Beijing, China
E-mail: [email protected]
Xiangheng Wang
Tsinghua University
100084, Beijing, China
E-mail: [email protected]
ISBN 978-7-302-19342-5
Tsinghua University Press, Beijing
ISBN 978-3-642-01152-8 e-ISBN 978-3-642-01153-5
Springer Dordrecht Heidelberg London New York
Library of Congress Control Number: pending
© Tsinghua University Press, Beijing and Springer-Verlag Berlin Heidelberg 2009
This work is subject to copyright. All rights are reserved, whether the whole or part of the material is
concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation,
broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication
of this publication or parts thereof is permitted only under the provisions of the German Copyright
Law of September 9, 1965, in its current version, and permission for use must always be obtained
from Springer-Verlag. Violations are liable to prosecution under the German Copyright Law.
The use of general descriptive names, registered names, trademarks, etc. in this publication does not
imply, even in the absence of a specific statement, that such names are exempt from the relevant
protective laws and regulations and therefore free for general use.
Cover design:Frido Steinen-Broo, EStudio Calamar, Spain
Printed on acid-free paper
Springer is a part of Springer Science+Business Media (www.springer.com)
Abstract
This book is written on the basis of the authors’ achievements in teaching and
research over many years in the field of ac machines and systems at Tsinghua
University, and reflects the new developments in and applications of science and
technology in recent years. When researching on the systems related to ac
machines as main roles, analysis methods and operating performance are stressed
in this book.
This book is divided into six chapters. Chapter 1 makes salient-pole electric
machines as the main subject of study. Considering ac machine as a circuit model
composed of stator and rotor having relative motion, and starting from a single
coil, the mathematic models and parameter calculation methods are discussed.
Chapter 2 discusses electromagnetic relations and parameters of synchronous
machines and their several operating conditions at synchronous speed, such as
3-phase sudden short circuit, sudden increase of load, opening short circuit, etc.
Chapter 3 introduces some special operating modes of synchronous machine
systems at constant speed and variable speed, such as two phase sudden short
circuit, asynchronous operation of synchronous machines, asynchronous starting
of synchronous motors, synchronous machine in connection with capacitances,
cycloconverter-fed synchronous motor, ac-dc hybrid loads of synchronous
machines, etc. Chapter 4 analyses oscillation, stability and excitation regulation
of synchronous machine systems. Chapter 5 introduces electromagnetic relations
of induction machines, some of their operating modes, such as starting
characteristics, reswitching process, self-excitation during motor in series with
capacitances, and combination system for polyphase induction generator with
dual windings and rectified load. Chapter 6 provides description of inner asymmetric
problems in the stator winding and squirrel-cage rotor of ac machines.
This book is a textbook for the postgraduates in the field of electric machines
and control, and also a reference book for technicists as well as for the teachers
and students of relevant specialties in universities and colleges.
i
Preface
With the increase of single unit capacity and broader application scope of ac
machines, as well as the development and application of power electronics,
computer, micro-electronic technology and control theory, the operating conditions
of ac machines and systems become more complicated, their automation level is
higher, and their operation demands are also stricter. Therefore, new projects and
new research results are presented one by one.
With development of science and technology, more attention has been paid to
the performance analysis of the following systems: variable speed drive system
of ac machines with power electronics and control devices, power energy system
composed of ac machines and power transmission lines, electric machine system
consisting of ac machines and excitation control devices. Therefore, a monographic
book on ac machine systems is needed urgently to reflect the new demand and
new developments.
This monographic book is written mainly on the basis of the following 5
monographic books: Analysis of AC Machines and Their Systems (1st Edition) in
1993 and 2nd Edition in 2004, Fundamental Theory and Analysis Methods of
Transients in Electric Machines Volume(cid:265)in 1982 and Volume(cid:266) in 1983, AC
Machine Transients and Operating Modes Analysis in 1963, in which the first
book was awarded the First Prize of National Excellent Science and Technology
Book in 1995 and the third and fourth books also won the First Prize of National
Excellent Science and Technology Book in 1983, together with the Excellent
Prize of National Teaching Material in 1988. The first, third, and fourth books
were finished under the leadership of Professor Gao Jingde, and the fifth book
was also written by Prof. Gao, a Member of Chinese Academy of Sciences,
the former President of Tsinghua University, Fellow of IEEE, and the founder of
transient theory of electric machines and power systems in China.
For international academic exchange, this monographic book has been written
in English. Professor Wang Xiangheng wrote Chapters 1 and 6 (except for
Sections 6.2 and 6.3), Dr. Wang Shanming wrote Section 3.7, Dr. Wu Xinzhen
iii
wrote Section 5.6, Dr. Sun Yuguang wrote Sections 6.2 and 6.3 and Professor
Zhang Linzheng wrote Preface, Introduction, Appendices and Chapters 2, 3, 4
and 5 (except Sections 3.7 and 5.6) together with modifying and unifying all
chapters in this book.
In the process of compiling this book, some books and papers were referred to,
and some books and papers written by our colleagues were also used. Main part
of them have been listed in the references in order to help the readers know their
origins and learn about some interesting problems in more depth. We are grateful
to the authors of those books and papers, especially to our colleagues.
It is very difficult to avoid defects and careless omissions in this book owing
to the finite acquirements of the authors although we have made our efforts.
Please send your comments and suggestions regarding this book to Department
of Electrical Engineering, Tsinghua University, Beijing, China.
Authors
iv
Introduction
AC machines are basic equipment of electric energy production and application.
Electric energy used in industry, agriculture and daily life is mostly produced by
alternators and the generated electric energy is likely utilized through ac motors.
The capacity of a single unit has been increased greatly for modern alternators,
the application domain is extended day by day, the automation grade of ac
machine systems is heightened increasingly, and the operating condition is more
complicated. Therefore, it is very important for electro-technical experts to
understand and master the operating performance and the analysis method of ac
machine system.
The ac machine system is a relatively mature but quickly developing product
of science and technology. Emergence and development of ac machines have a
history of more than one hundred years, in which ac machines of various types
have been built for various uses. During design, manufacture, and operation of ac
machines and through researches and improvement, people have comprehended
the structure principles, manufacture technique, and operating performance
deeply. However, due to restraints of technical development and research
conditions in the past, people paid attention to normally operating performance,
outer faults and economic parallel-operation in safety for ac machines, which is
natural because those problems often exist in practice.
During the past decades, the power electronic technique has been widely used,
the dc transmission had a great progress, ac-dc hybrid transmission systems
emerged, large capacity alternators were built to bring about some new requirements,
and modern control theory, micro-electronics and computer technology also
progressed greatly, thus making the theory and operating performance of ac
machine systems undergo a new development. For example, the analysis of inner
unsymmetrical windings, the study of control system consisting of ac machines,
power electronic devices, micro-electronics and computer technology, the analysis
of electromagnetic harmonics effect and restraint are all the new topics.
During the operation of the ac machine, due to manufacturing defect or
misoperation, some fault occurs in the machine winding that creates unnecessary
loss. For large hydraulic generator, its stator winding often has multi-branches. If
inter-turns or inter-phases short circuit occurs or the winding is broken partly, the
large fault current will damage the winding or the iron core, and the negative
v
sequence magnetic field during fault may burn the rotor too. When the
turbo-generator and the induction machine are working, some serious inner faults
may occur in their stator winding. As far as the rotor of an ac machine is
concerned, weld defects, and the breaking or short circuit of conductors may
occur, too. Therefore, it is necessary to study the various state quantities during
inner faults in order to understand the harm of faults, to improve the design and
manufacturing technology and to put forward the corresponding protection relays.
So far as the dc transmission system goes, due to the combination of alternator
and rectifiers, it is quite different from the ac transmission system. As for the
alternator, it is often on unsymmetrical operating mode and in the system exist
serious harmonics due to nonlinearity of rectifying elements, so the corresponding
special topics need studying. In addition, the ac excitation system is widely used
and sometimes the excitation bars are installed in the upper positions of stator
slots for the main alternator to provide excitation current for the excitation
system of main alternator through the rectifiers, which also brings about the
similar problems as mentioned above.
Since they connect computer, micro-electronics and power electronic technique,
the speed regulation and control of ac motors have been developed swiftly, and
some electromagnetic processes, which were hardly measured and controlled in
the past, can be regulated and controlled today through on-line measurement,
computer analysis and control.
With the development of computer technology and the application of numerical
method, some problems of the electromagnetic field of an electric machine, which
were hardly calculated in the past, can be solved today to enhance the capability
of design and operating performance analysis, and the accuracy of parameters
calculation greatly for ac machines. In addition, the achievements in some aspects
are also gotten, such as pole-changing speed-regulation of induction motors,
principles and methods of starting, the combination of capacitors and stator
winding, special machine provided with rectangular waveform current, storage
electric machine, etc.
For a deep analysis of the ac machine systems, it is necessary to put forward
new theory and methods.
As you know, as far as the electromagnetic relation of ac machine is concerned,
it can be considered as the combination of several coils coupled magnetically and
studied according to usual circuit rules. However, due to rotor rotation, there
exists relative motion between those coils. 3-phase symmetrical winding is adopted
for the stator winding of an ac machine to make the air-gap magnetic field be of
sinusoidal waveform and revolve synchronously when 3-phase symmetrical
current passes through the 3-phase winding. In so doing, various targets of ac
machines are all good. Therefore, people used to assume the air-gap flux to be
sinusoidal and to merge small harmonic flux into leakage flux during the analysis
of ac machines. Analyzing their operating performance, the parameters used are
based on the criterion that they can reflect the total action of the air-gap magnetic
vi
field, such as d- and q-axes armature reaction reactances x and x for
ad aq
synchronous machines, magnetization reactance x for induction machines,
m
etc. Correspondingly, other parameters such as x ,x ,x(cid:99),x(cid:99),x(cid:99)(cid:99) and x(cid:99)(cid:99) for
d q d q d q
synchronous machines, are all some values to reflect the total electromagnetic
effect. The mathematical patterns built by using the above parameters and the
corresponding analytical results can meet the practice requirements; so in the
text-books and references, the phase winding has been the basis and the total
effect of multiphase winding has been taken to analyze ac machines for many
years.
As stated before, with the development of science and technology, there came
to exist the inner unsymmetrical problem of electric machine winding, the new
combination system of electric machine and power electronic devices and some
electric machines of special structure, which make taking a single machine as the
analysis object and symmetrical phase winding as the basis of theory and
methods be unsuitable for the study of some topics. Thus, it is necessary to take
the electric machine and the associated outer devices as a system to consider the
influence of electromagnetic harmonics. Based on the aforementioned points, a
single coil is adopted as the basis in this book to describe the basic electromagnetic
relation of ac machines and to build the corresponding expressions. After getting
the relations, they can be used to study not only the problems that are analyzed
by using the existing methods but also some new topics as mentioned before.
Since the basic electromagnetic relations of ac machines are based on single coil,
in the light of the requirements for different research problems compose the
corresponding loops to get the associated electromagnetic relations, inclusive of
the electromagnetic relations obtained when taking the phase winding as the
basis. Because electromagnetic harmonics are counted in the basic relations, we
can study not only some topics which need to count harmonic influence but also
a certain problem that can neglect harmonic effect for convenience.
The ac machine parameters used in the new method are self inductances and
mutual inductances for various coils, so it is not difficult to find out the
parameters and the basic relations to reflect the total electromagnetic effect of ac
machine winding according to the self inductances and mutual inductances if
necessary.
The study starts from a single coil and combines the corresponding loop
equations according to the actual loops connection of ac machines to research
into needful topics, which is termed the Multi-Loop Theory and is the main basis
of this book.
This book is divided into six chapters, referring to Contents of this book in detail.
Firstly, based on a single coil and using the Multi-Loop Theory created by
some authors of this book, we get various inductances and parameters which are
the same as classical method, and then analyze several operating modes of
synchronous machine systems, such as transformations of reference axes systems
connecting the relevant mmf to form a clear concept, short circuit and
vii