UNIVERSITI PUTRA MALAYSIA
APPLICATION OF ROBUST CONTROLLER IN LARGE INDUCTION MOTOR FOR MITIGATING VOLTAGE SAGS
MAHDI HEDAYATI
FK 2012 114
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APPLICATION OF ROBUST CONTROLLER IN LARGE INDUCTION
MOTOR FOR MITIGATING VOLTAGE SAGS
By
MAHDI HEDAYATI
Thesis Submitted to the School of Graduate Studies, University Putra Malaysia,
in Fulfillment of The Requirements for the Degree of Doctor of Philosophy
February 2012
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Dedicated to my wife Maryam for her immense patience and allegiance while
studying my PhD specially during the last year and to my son Hirad for his love
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Abstract of thesis presented to the Senate of Universiti Putra Malaysia
in fulfillment of the requirement for the degree of Doctor of Philosophy
APPLICATION OF ROBUST CONTROLLER IN LARGE INDUCTION
MOTOR FOR MITIGATING VOLTAGE SAGS
By
MAHDI HEDAYATI
February 2012
Chairman: Norman Mariun, PhD
Faculty: Faculty of Engineering
This research presents a new study on robust controller based on loop shaping
procedure for a static synchronous compensator (STATCOM) installed at terminals
of the large induction motor.
The space vector pulse width modulation (SVPWM) drive system is one of the most
significant apparatus in industrial application of induction motors that utilization of
this equipment is considered in this thesis and compared with static var compensator
(SVC) installed at terminals of motor. It is shown that the dynamic behaviour and
performance of SVC is better than SVPWM drive system for starting of the induction
motor, so the time for motor speeding up is slower with lower transients, while the
variations of induction motor current are in the sufficient range.
A comparison between proportional-integral (PI) controllers of different shunt
flexible alternating current transmission systems (FACTS) shows that STATCOM is
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more effective and has a better dynamic performance than SVC, so the parameters of
peak time and voltage sag by using the STATCOM for starting of large induction
motor without and with load are significantly decreased. The results from simulations
prove that STATCOM is significantly proficient to ensure good power quality and
more effective than SVC for decreasing transients, voltage profile improvement and
getting better dynamic behavior of motor‟s rotor speed while symmetrical and
unsymmetrical voltage sags are considered.
Whereas FACTS devices have nonlinearity nature; using the conventional PI control
theory with system linearization around nominal point is not a suitable method,
besides, there exists the uncertainty in the system. So developed robust control theory
that covers stability and performance criteria under all system uncertainties, has been
applied for the controller design in power system to assure fast and stable regulation
under wide range of operating circumstances.
Among the different robust methods used to design the controller of shunt FACTS,
loop shaping procedure is known to be one of the effective and feasible control
methods. So this method is considered to simulate robust controller for STATCOM
installed at terminals of the large induction motor. The dynamic behaviors of
induction motor are analyzed while the uncertainty of system parameters,
STATCOM parameters and external disturbances are considered. Besides, in all
previous research works, a robust control design using loop shaping method
through Graphical Loop Shaping (GLS) technique or Normalized Coprime
Factorization (NCF) approach is proposed. In this thesis, both mentioned methods
have been considered in the design of robust controller and have been compared
together and with conventional PI controller.
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It is clearly observed that the output response of robust controllers using GLS and
NCF methods are similar and surely have better dynamic performances than PI
controller. A development has been determined that GLS method is more robust than
NCF against variations of system parameters and STATCOM parameters. PI
controller is not very strong against changing of system parameters and STATCOM
parameters when compare with GLS and NCF methods, even the system goes to
instability for a certain operating point.
Another development will be presented when these robust controllers and
conventional PI controller are tested for external disturbances consist of a load
disturbance and a sinusoidal disturbance on system performance. The results of
simulations prove that all controllers are able to damp these disturbances, but both
GLS and NCF methods are more robust than PI controllers to remove these
perturbations. It is obviously shown that GLS method has better dynamic
performance than NCF method to reject the disturbances and stronger than NCF
method against load disturbance and sinusoidal disturbance uncertainties.
Finally, for validation of the designed systems, this research is compared with other
works. It is concluded that results of the designed controllers for SVC and
STATCOM having parameters and specifications of other research works are similar
with the simulation results of the mentioned work.
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Abstrak of tesis yang dikemukakan kepada Senat Universiti Putra Malaysia
sebagai memenuhi keperluan untuk ijazah Doktor Falsafah
APLIKASI ALAT KAWALAN TEGAR PADA MOTOR INDUKSI BESAR
UNTUK MENGURANGKAN PENURUNAN VOLTAN
Oleh
MAHDI HEDAYATI
Februari 2012
Pengerusi: Norman Mariun, PhD
Fakulti : Fakulti Kejuruteraan
Penyelidikan ini mengetengahkan kajian baru dalam alat kawalan tegap
berdasarkan prosedur pembentukan untuk pemampas statik segerak atau “static
sysnchronous compensator (STATCOM)” yang dipasang pada terminal motor aruhan
yang besar.
Sistem pemacu ruang vektor modulasi lebar denyut atau “space vector pulse width
modulation (SVPWM)” ada salah satu perkakas yang paling penting di dalam
aplikasi industri motor aruhan yang mana penggunaan perkakas ini diambil kira di
dalam tesis ini dan perbandingan dibuat diantara pemampas statik var atau “static var
compensator (SVC)” yang dipasang pada terminal motor. Hasil kajian menunjukkan
kelakuan dinamik dan prestasi SVC lebih baik daripada sistem pemacu SVPWM
untuk memulakan motor aruhan, oleh itu masa untuk motor memecut adalah lebih
perlahan dengan sambutan fana yang lebih rendah, sementara variasi arus motor
aruhan berada di dalam julat yang mencukupi.
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Perbandingan di antara alat kalawan kamiran berkadaran atau “proportional-integral
(PI)” konvensional yang mempunyai pirau sistem transmisi arus ulang-alik boleh
ubah atau “flexible alternating current transmission systems (FACTS)” berbeza
menetapkan STATCOM adalah lebih berkesan dan mempunyai prestasi dinamik
yang lebih baik berbanding SVC, oleh itu pembolehubah masa puncak dan voltan
lendut yang menggunakan STATCOM untuk memulakan motor aruhan yang besar
dengan dan tanpa beban didapati berkurangan dengan ketara. Keputusan dari
simulasi membuktikan STATCOM adalah sangat cekap untuk memastikan kualiti
kuasa yang baik dan lebih berkesan berbanding SVC bagi sambutan fana yang
menurun, pembaikan taraf voltan dan mendapat kelakuan dinamik yang lebih baik
bagi kelajuan motor semasa voltan simetri dan tidak simetri diambil kira.
Sementara perkakas FACTS semulajadi tidak linear; menggunakan teori kawalan PI
konvensional dengan pelinearan sistem lingkungan titik nominal adalah tidak sesuai,
Di samping itu, terdapat ketidakpastian di dalam sistem. Oleh yang demikian, teori
kawalan tegar sedia ada yang meliputi kestabilan dan ciri-ciri prestasi di bawah
keseluruhan ketidakpastian sistem, telah digunakan untuk rekaan alat kawalan di
dalam sistem kuasa untuk memastikan pengaturan yang cepat dan stabil di bawah
julat keadaan operasi yang besar.
Di antara kaedah tegar berbeza yang digunakan untuk mereka bentuk alat
kawalan pirau FACTS, prosedur pembentukan gelung dipilih sebagai kaedah
terbaik untuk mereka bentuk alat kawalan. Oleh itu, kaedah ini diambil kira untuk
mesimulasi alat kawalan tegar untuk STATCOM yang dipasang pada terminal motor
aruhan yang besar. Kelakuan dinamik motor aruhan dianalisa sementara
ketidakpastian pada pembolehubah sistem, pembolehubah STATCOM dan gangguan
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luaran diambil kira. Di samping itu, di dalam semua kajian yang lalu, Rekaan alat
kawalan tegar menggunakan kaedah pembentukan gelung melalui teknik
pembentukan gelung geraf atau “ Graphical Loop Shaping (GLS)” atau pendekatan
faktor co-prima nominal atau Normalized Coprime Factorisation (NCF) telah
dicadangkan. Di dalam tesis ini, kedua-dua kaedah tersebut telah dibandingkan
bersama alat kawalan PI konvensional.
Adalah didapati bahawa sambutan luaran alat kawalan tegar menggunakan kaedah
GLS dan NCF hampir sama dan sudah pasti mempunya prestasi dinamik yang lebih
bagus berbanding alat kawalan PI. Pembangunan telah dikenal pasti bahawa kaedah
GLS adalah lebih tegar berbanding NCF berhadapan variasi pembolehubah sistem
dan STATCOM. Alat kawalan PI tidak begitu kuat berhadapan perubahan
pembolehubah sistem dan pembolehubah STATCOM apabila dibandingkan dengan
kaedah GLS dan NCF, walaupun sistem itu tidak stabil untuk titik operasi yang pasti.
Satu lagi keadaan dibentangkan apabila alat kawalan tegar dan alat kawalan PI
konvensional diuji dengan gangguan luaran yang mengandungi gangguan beban dan
gangguan sinusoid ke atas prestasi sistem. Keputusan simulasi membuktikan
kesemua alat kawalan boleh mengatasi gangguan-gangguan ini, tetapi kaedah GLS
dan NCF lebih tegar berbanding alat kawalan PI untuk menghilangkan usikan
tersebut. Jelas sekali kaedah GLS mempunyai sambutan dinamik yang lebih baik
berbanding kaedah NCF untuk melenyapkan gangguan dan lebih kuat dari NCF
berhadapan gangguan beban dan gangguan ketidakpastian sinusoid.
Akhir sekali, untuk mengesahkan sistem yang telah direka bentuk, penyelidikan ini
dibandingkan dengan hasil penyelidikan lain. Kesimpulannya, keputusan dari alat
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kawalan SVC dan STATCOM yang mempunyai pembolehubah dan spesifikasi yang
sama dengan hasil penyelidikan terdahulu adalah setara dengan keputusan yang
diperole.
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ACKNOWLEDGEMENTS
First and foremost, deepest gratitude to the Most Gracious and Most Merciful Allah
s.w.t for giving me the strength and determination to complete this work.
It is an honour and pleasure to be working with Prof. Ir. Dr. Norman Mariun as the
supervisor. I am grateful to him, for the time and energy spent during the undertaking
of the degree. I also value his advices, guidance and experiences given to me
throughout the duration of the research work and writing the thesis.
I would also like to express deepest thanks to Assoc. Prof. Dr. Hashim Hizam,
Assoc. Prof. Dr. Samsul Bahari Mohd. Noor and Assoc. Prof. Dr. Senan Mahmod
Abdollah for their suggestions and comments, and also being in the supervisory
committee.
Last but not least, to my families, thank you for the prayers and encouragements that
have given to me all these years and of course not forgetting my wife and son for
their love and understanding.
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I certify that a Thesis Examination Committee has met on 17 February 2012 to
conducts the final examination of Mahdi Hedayati on his thesis entitled” Application
of Robust Controller in Large Induction Motor in Mitigating Voltage Sags” in
accordance with the universities and university colleges Act 1971 and the Constitution
of the Universiti Putra Malaysia [P.U. (A) 106] 15 March 1998. The Committee
recommends that the student be awarded the Doctor of Philosophy.
Members of the Examination Committee were as follows:
Chandima Gomez, PhD
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Mohammad Hamiruce Marhaban, PhD
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Internal Examiner)
Ishak Aris, PhD
Professor
Faculty of Engineering
Universiti Putra Malaysia
(Internal Examiner)
Mohamed El-Hawari, PhD
Professor
Faculty of Engineering
Dalhousie University, Halifax, NS, Canada
(External Examiner)
SEOW HENG FONG, PhD
Professor and Deputy Dean
School of Graduate Studies
Universiti Putra Malaysia
Date:
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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been
accepted as fulfillment of the requirement for the degree of Doctor of Philosophy.
The members of the Supervisory Committee were as follows:
Norman Mariun, PhD
Professor
Faculty of Engineering
University Putra Malaysia
(Chairman)
Hashim Hizam, PhD
Associate Professor
Faculty of Engineering
University Putra Malaysia
(Member)
Samsul Bahari Mohd. Noor, PhD
Associate Professor
Faculty of Engineering
University Putra Malaysia
(Member)
Senan Mahmod Abdollah, PhD
Associate Professor
College of Electronic Engineering
University of Mosul, Iraq
(Member)
BUJANG BIN KIM HUAT, PhD
Professor and Dean
School of Graduate Studies
Universiti Putra Malaysia
Date:
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DECLARATION
I declare that the thesis is my original work except for quotations and citations which
have been duly acknowledged. I also declare that it has not been previously, and is
not concurrently, submitted for any other degree at Universiti Putra Malaysia or at
any other institution.
MAHDI HEDAYATI
Date: 17 February 2012
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TABLE OF CONTENTS
Page
DEDICATIONS ii
ABSTRACT iii
ABSTRAK vi
ACKNOWLEDGEMENTS x
APPROVAL xi
DECLARATION xiii
LIST OF TABLES xvii
LIST OF FIGURES xix
LIST OF ABBREVIATIONS xxiv
CHAPTER
1 INTRODUCTION
1.1 Background 1
1.2 Problem Statement 4
1.3 Aim and Objectives 7
1.4 Project Scope 8
1.5 Thesis Layout 10
2 LITERATURE REVIEW
2.1 Introduction 13
2.2 STATCOM 14
2.2.1 Basic Concept 14
2.2.2 STATCOM Model 15
2.2.3 Control Strategies 18
2.3 Comparison of SVC and STATCOM 18
2.4 Power Quality Improvement and Voltage Sags Mitigation
by STATCOM
20
2.5 Power Quality Study and Induction Motor Starting with
SVC, STATCOM and Drive System
22
2.5.1 Power Quality Effect on Performance of
Induction Motor
22
2.5.2 Starting of Induction Motors with SVC and
STATCOM
25
2.5.3 Induction Motor Drive System 28
2.6 Study of Different Control Methods in the Application of
STATCOM and Other FACTS Devices
30
2.7 Application of Robust Control Techniques to Power
Systems
32
2.7.1 Uncertainty Model 33
2.7.2 Robust Stability and Robust Performance 35
2.7.3 Comparison of Different Robust Methods 36
2.7.4 Robust Controller using Loop Shaping
Procedure
40
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2.8 Summary 47
3 METHODOLOGY
3.1 Introduction 50
3.2 System Modeling 53
3.2.1 Motor Model 54
3.2.2 SVC Model 55
3.2.3 STATCOM Model 56
3.2.4 Transmission Line Model 57
3.2.5 Lineraized Model 58
3.2.5.1 Linearized Model of System
with SVC 59
3.2.5.2 Linearized Model of System
with STATCOM
61
3.3 Design of Conventional PI Controller 65 3.4 Operation of Induction Motor with Shunt FACTS
Under Different Voltage Sag Circumstances
67
3.5 Loop Shaping Robust Control Design 68
3.5.1 Graphical Loop Shaping (GLS) Method 70
3.5.1.1 Uncertainty Modeling 71
3.5.1.2 Robust Stability and Robust
Performance Criteria
72
3.5.1.3 GLS Technique 77
3.5.1.4 The Algorithm of GLS Procedure
Based on Theory
78
3.5.2 Normalized Coprime Factorization (NCF) Method 81
3.5.2.1 Loop Shaping 81
3.5.2.2 Robust stabilization 83
3.5.2.3 The Algorithm of Control
via NCF Approach
86
3.6 Summary 87
4 RESULTS AND DISCUSSIONS
4.1 Introduction 89
4.2 SVPWM, SVC and STATCOM Results and Discussions 90
4.2.1 Comparing SVC with SVPWM 91
4.2.2 Comparing STATCOM and SVC 97
4.2.2.1 Starting of Induction Motor without
Compensator under Ideal Supply
condition
97
4.2.2.2 Starting of Induction Motor with
SVC under Ideal Supply condition 100
4.2.2.3 Starting of Induction Motor with
STATCOM under Ideal Supply
condition
102
4.2.2.4 Starting of Induction Motor with Load 103
4.2.2.5 Induction Motor in Load Varying State 105
4.2.2.6 Validation of Designed System
with SVC 106
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4.2.2.7 Starting of Induction Motor under
Symmetrical Voltage Sag Condition
110
4.2.2.8 Starting of Induction Motor under
Unsymmetrical Voltage Sag Conditions
112
4.3 Robust Controller Results and Discussions 120
4.3.1 GLS Method 120
4.3.1.1 Step Response of Motor‟s
Rotor Speed ( 121
4.3.1.2 Step Response of Motor‟s
Terminal Voltage ( 130
4.3.2 NCF Method 136
4.4 PI Controller Results and Discussions 144
4.5 Load Disturbance and Sinusoidal Disturbance 150
4.6 Validation of Designed System and Comparison with a fuzzy
controller for STATCOM
156
4.6.1 Validation of Designed System with STATCOM 156
4.6.2 Comparison with a fuzzy controller for
STATCOM
162
4.7 Summary 165
5 CONCLUSION AND FUTURE WORKS
5.1 Conclusion 169
5.2 Future Works and Recommendations 173
REFERENCES 175
APPENDICES
Appendix A1. Calculations of Matrices , ,
and
185
Appendix A2. Calculations of Matrices , ,
and
194
Appendix A3. Calculations of Matrices , ,
and
205
Appendix A4. The effect of transmission line resistance (
on the performance of large induction motor
216
Appendix B1. Parameters of different systems
for simulation studies
217
Appendix B2. Calculations of and of PI controllers
( chapter 3)
221
Appendix B3. Calculation of in GLS method (chapter 4) 233
BIODATA OF STUDENT 237
LIST OF PUBLICATIONS 238