universiti putra malaysia application of robust controller in large

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



(Internal Examiner)

Ishak Aris, PhD

Professor



(Internal Examiner)

Mohamed El-Hawari, PhD

Professor


Dalhousie University, Halifax, NS, Canada

(External Examiner)

SEOW HENG FONG, PhD

Professor and Deputy Dean

School of Graduate Studies


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


University Putra Malaysia

(Chairman)

Hashim Hizam, PhD

Associate Professor



(Member)

Samsul Bahari Mohd. Noor, PhD

Associate Professor



(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


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


and

194


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

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universiti putra malaysia application of robust controller in large