power quality improvement by dynamic voltage...
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POWER QUALITY IMPROVEMENT BY DYNAMIC VOLTAGE RESTORER
AND UNIFIED POWER QUALITY CONDITIONER USING FUZZY LOGIC
FARIDULLAH KAKAR
A thesis submitted in fulfilment of the
requirements for the award of the degree of
Master of Engineering (Electrical)
Faculty of Electrical Engineering
UniversitiTeknologi Malaysia
SEPTEMBER 2015
iii
I dedicate this thesis to my friend Abdul RehmanAl-Najjar (deceased), my wife and
my sons, Shamsher Ali Khan and Altamash Ali Khan
iv
ACKNOWLEDGEMENT
In the name of Allah almighty, the most Beneficent and the most Merciful.
With gratitude to Allah for His mercy that has given me strength, patience,
perseverance and health for timely completion of this imperative assignment.
Guidance of our Holy Prophet Hazrat Muhammad (S.A.W), throughout my life and
in this task in particular, is truly acknowledged. After that patronage, support and
backing of my supervisor Dr. Mohd Hafiz Bin Habibuddin and co-supervisor Prof.
Ir. Dr. Abdullah Asuhaimi Bin Mohd Zin is undeniable. Their encouragement and
support not only enabled me pursue new ideas but also facilitated my self
confidence. Notably, their incisive feedback afforded me to progress in the precise
direction. This task could not have been accomplished without their keen
observations, incessant advices, and persistent suggestions in each and every part of
this work.
I would like to thank every person involved in the proceedings of this final
project report preparation. I would like to extend my special gratitude to Mr. Abdul
Rehman Al-Najjar (deceased) for motivating me to proceed in the right direction
whenever I wavered.
I am greatly indebted to UniversitiTeknologi Malaysia for providing me the
platform. My sincerest thanks to Dr. Mahmoud Pasaran, Mr. SohailKhokhar and all
my colleagues and laboratory mates for their help and support. Finally, I truly
endorse the warm backing and care of my family exclusively my wife whose endless
support enhanced my agility to make her dream come to reality. I also salute my two
sons for all the bears for the sake of my studies.
v
ABSTRACT
Voltage sag and harmonics have significant negative impact on power
quality. Propagation of distorted waveform in the system ultimately instigates a
range of power quality issues. Protection against this situation is necessary because it
adversely affects reliability and quality of power supply. Custom Power Devices
(CPD) such as Dynamic Voltage Restorer (DVR) and Unified Power Quality
Conditioner (UPQC) provide a level of reliability and power quality that is urgently
required. The basic purpose of this thesis is to implement new control strategies to
mitigate voltage sag/swell and to suppress harmonics to evaluate CPD performance.
The CPD system is controlled by Fuzzy Logic Controllers (FLCs) with 49 rules and
25 rules, respectively and their performances are compared with Proportional
Integral (PI) controller. This thesis focuses on FLC with fewer rules to avoid
complexity, reduce computation time and consume less memory space. The proposed
strategy depends on d-q transformation, phase-locked loop synchronization and
constant DC link voltage. Simulation results depict better reliability of fuzzy logic
techniques with non-linear loads when compared with PI technique. The capability
of DVR and UPQC using FLC especially with fewer rules is demonstrated using test
models built in Matlab/Simulink software. Both equipments potentially restore sags
and improve overall harmonic profile while reducing total harmonic distortion to
values within the prescribed criterion set by IEEE standards. The proposed FLC
approach with reduced rule base, is superior to PI and FLC with 49 rules, assures
effective performance, with normalization and tuning of parameters especially the
membership functions and scaling factors. It yielded excellent voltage profile with
best possible compensation during system contingencies, conforming to the IEEE
standards that affirm FLC as an effective solution for power quality problems.
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ABSTRAK
Voltan lendut dan harmonik mempunyai kesan negatif yang signifikan
terhadap kualiti kuasa. Perambatan gelombang terherot dalam sistem peda akhirnaya
menyebabkan pelbagai isu kualiti kuasa yang lain. Perlindungan terhadap keadaan ini
adalah perlu kerana ia memberi kesan buruk terhadap kebolehpercayaan dan kualiti
bekalan kuasa. Peranti Kuasa Langganan (CPD) seperti Pemulih Voltan Dinamik
(DVR) dan Penyesuai Kualiti Kuasa Disatukan (UPQC) menyediakan tahap
kebolehpercayaan dan kualiti kuasa yang amat diperlukan. Tujuan asas tesis ini
adalah untuk melaksanakan strategi kawalan baru untuk mengurangkan voltan lendut
dan menyekat harmonik bagi menilai prestasi CPD. Sistem CPD dikawal oleh
pengawal logik kabur (FLC) dengan 49 peraturan dan 25 peraturan, dan prestasi
mereka dibandingkan dengan pengawal kamiran berkadaran (PI). Tesis ini
menumpukan kepada FLC dengan peraturan yang sedikit untuk mengelakkan
kekompleksan, mengurangkan masa pengiraan dan menggunakan ruang memori yarg
kecil. Strategi yang dicadangkan bergantung kepada transformasi d-q, penyegerakan
Gelung Terkunci Fasa dan voltan pautan DC malar. Keputusan simulasi
menunjukkan kebolehpercayaan yang lebih baik dengan teknik logik kabur dengan
beban tidak linear berbanding teknik PI. Keupayaan DVR dan UPQC menggunakan
FLC khususnya dengan bilangan peraturan yang rendah ditunjukkan menggunakan
model ujian dibina dalam perisian Matlab / Simulink. Kedua-dua peralatan
berpotensi menghilangkan lendut dan meningkatkan keseluruhan profil harmonik di
samping mengurangkan Jumlah Herotan Harmonik kepada nilai-nilai dalam kriteria
yang ditetapkan oleh piawaian IEEE. Pendekatan FLC yang dicadangkan dengan
asas peraturan yang dikurangkan, PI dan FLC yang baik dengan 49 peraturan akan
memastikan prestasi yang berkesan, dengan penormalan dan penalaan parameter
terutama rangkap keahlian dan faktor penskalaan, menghasilkan pengaturan voltan
yang sangat baik dan meningkatkan profil voltan sewaktu kesilapan diluar jangkaan
sistem, yang mematuhi piawaian IEEE dan mengesahkan FLC sebagai penyelesaian
yang berkesan untuk masalah kualiti kuasa.
vii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES xiii
LIST OF ABREVIATIONS xviii
LIST OF SYMBOLS
LIST OF APPENDICES
xxi
xxii
1 INTRODUCTION 1
1.1 Background of Study 1
1.2 Problem Statement 5
1.3 Objectives of the Research 6
1.4 Scopes of the Research 6
1.5 Significances of the Research 7
1.6 Organization of Thesis 8
2 LITERATURE REVIEW 9
2.1 Power Quality (PQ) 9
2.2 Main PQ Sources, Causes and Effects 10
2.3 Solutions and methods to Improve PQ 10
2.4 Custom Power Devices (CPD) 11
2.4.1 Dynamic Voltage Restorer (DVR) 12
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2.4.1.1 Principle of Operation 12
2.4.1.2 Operating Modes of DVR 13
2.4.1.3 Configuration of DVR 15
2.4.2 Unified Power Quality Conditioner
(UPQC) 17
2.4.2.1 Basic Configuration of
UPQC 18
2.4.2.2 Series and Shunt APF’s
ratings in UPQC 19
2.4.2.3 Functions performed by
UPQC 20
2.5 Control issues related to DVR and UPQC 21
2.5.1 Review of DVR Controllers 23
2.5.1.1 PI Controller 23
2.5.1.2 Repetitive controller 28
2.5.1.3 Proportional Resonant (PR)
controller
28
2.5.1.4 Hysteresis Controller 29
2.5.1.5 Optimal Predictive Control
(OPC) 30
2.5.1.6 Adaptive Neuro-Fuzzy
Inference System (ANFIS)
31
2.5.1.7 Fuzzy Logic Control (FLC) 32
2.5.2 Review of UPQC Controllers 33
2.5.2.1 Proportional-Integral-
Derivative (PID) & PI
controllers 33
2.5.2.2
2.5.2.3
2.5.2.4
2.5.2.5
Hysteresis controller
Power Angle Control
(PAC)
Pulse Width Modulation
(PWM)
Synchronous Reference
Frame (SRF)
35
38
39
39
2.5.2.6 Artificial Nueral Netwok
(ANN) and Adaline 40
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2.5.2.7 Fuzzy Logic Control (FLC) 41
2.6 Summary 43
3 METHODOLOGY 45
3.1 Introduction 45
3.2 DVR Simulation Model 47
3.2.1 DVR Single-line Diagram 48
3.2.2 Proposed DVR Controls 51
3.2.2.1 Sag Detection 51
3.2.2.2 Reference Voltage
Compensation for PI
controller with PWM
generator 54
3.2.2.3 Reference Voltage
Compensation for FLC
with PWM Generator 57
3.3 UPQC Simulation Model 63
3.3.1 Control Philosophy 67
3.3.1.1 Shunt inverter reference
current detection ( d-q
Method) 68
3.3.2.2 Shunt inverter control based
on PWM 69
3.4 Summary 70
4 RESULTS AND DISCUSSIONS 72
4.1 DVR Simulation Results 72
4.1.1 Case 1: Linear load 72
4.1.2 Case 2: Non-linear load 78
4.1.3 Case 3: FOC-IM load 84
4.2 UPQC Simulation Results 89
4.2.1 Case 1: Linear load 90
4.2.2 Case 2: Non-linear load 101
4.2.3 Case 3: FOC-IM load 111
4.3 Comparison of DVR and UPQC for voltage
harmonics reduction 123
4.4 Comparison of FLC (49 rules) and FLC (25 124
x
rules) with DVR
4.5
4.6
4.7
4.8
4.9
Comparison of FLC (49 rules) and FLC (25
rules) with UPQC
Comparison of FLC (49 rules) and FLC (25
rules) with DVR in terms of Memory Space
Comparison of FLC (49 rules) and FLC (25
rules) with UPQC in terms of Memory Space
Comparison of FLC (49 rules) and FLC (25
rules) with DVR in terms of Computational
Time
Comparison of FLC (49 rules) and FLC (25
rules) with UPQC in terms of Computational
Time
125
.
126
127
128
128
4.10 Summary 129
5 CONCLUSIONS AND FUTURE WORK 131
5.1
5.2
Conclusion
Significant contribution of the Thesis
131
134
5.3 Future work 134
REFERENCES
Appendices A1-C1
134
144-151
xi
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Summary of main PQ problems, their causes and
effects 10
3.1 Parameters of DVR test system 49
3.2 FLC with 49 rules (Mac-vicar and Whelan decision
matrix) (Hilloowala and Sharaf (1996)) 59
3.3 FLC with 25 rules 62
3.4 UPQC system parameters 64
4.1
Summary of voltage THD for DVR with PI, FLC (49
and 25 rules) with linear load 77
4.2
Summary of voltage THD for DVR with PI, FLC (49
and 25 rules) with non-linear load 83
4.3
Summary of voltage THD for DVR with PI, FLC (49
and 25 rules) with FOC-IM load 88
4.4
Summary of voltage THD for UPQC with PI, FLC
(49 and 25 rules) with linear load 96
4.5
Summary of current THD for UPQC with PI, FLC
(49 and 25 rules) with linear load 99
4.6
Summary of voltage THD for UPQC with PI, with
FLC (49 and 25 rules) with non-linear load 107
4.7
Summary of current THD for UPQC with PI, with
FLC (49 and 25 rules) with non-linear load 110
4.8
Summary of voltage THD for UPQC with PI, with
FLC (49 and 25 rules) with FOC-IM load 118
4.9 Summary of current THD for UPQC with PI, with
FLC (49 and 25 rules) with FOC-IM load 121
4.10 Summary of voltage THD comparison of DVR and
UPQC with PI, with FLC (49 and 25 rules) 123
4.11 Summary of voltage THD comparison of FLC (49
rules) and FLC (25 rules) with DVR 124
4.12 Summary of voltage THD comparison of FLC (49 126
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4.13
4.14
4.15
4.16
rules) and FLC (25 rules) with UPQC
Summary of memory space comparison of FLC (49
rules) and FLC (25 rules) with DVR
Summary of voltage THD comparison of FLC (49
rules) and FLC (25 rules) with UPQC
Summary of computational time of FLC (49 rules)
and FLC (25 rules) with DVR
Summary of computational time of FLC (49 rules)
and FLC (25 rules) with UPQC
127
128
128
129
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LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 Protection mode of DVR (Kumari and Garg 2013) 14
2.2 Standby mode of a DVR (Ali, et al., 2013) 15
2.3 Basic DVR configuration (Dib, et al., 2011) 15
2.4 VSI using IGBT (Singh, et al., 2013) 16
2.5 Block diagram of UPQC (Axente, et al., 2011) 18
3.1 Research work flow chart 47
3.2 Single-line diagram of DVR test model 48
3.3 Matlab / Simulink DVR model 50
3.4 Matlab / Simulink Model for sag detection 52
3.5 Circuit Model of DVR Test System (Tiwari and Gupta
2010) 55
3.6 PI controller basic structure (Tiwari and Gupta 2010) 56
3.7 Phase-Modulation firing angle control δ (Kumar, S.
2007; Ganesh, S. et al., 2011] 57
3.8 FLC FIS editor 58
3.9 FLC MF’s editor, rule viewer and surface viewer 61
3.10 FLC simulink sub system for 25 rules 63
3.11 UPQC test system model 65
3.12 Matlab / Simulink UPQC model 66
4.1 Voltage waveform (a) without DVR (b) injected
voltage (c) with DVR for LG fault with linear load 73
4.2 Voltage waveform (a) without DVR (b) injected
voltage (c) with DVR for LLG fault with linear load 73
4.3 Voltage waveform (a) without DVR (b) injected
voltage (c) with DVR for LLLG fault with linear load 74
4.4 Voltage THD (a) without DVR (b) with DVR (c) with
FLC (49 rules) (d) with FLC (25 rules) for LG fault
with linear load 75
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4.5 Voltage THD (a) without DVR (b) with DVR (c) with
FLC (49 rules) (d) with FLC (25 rules) for LLG fault
with linear load 75
4.6 Voltage THD (a) without DVR (b) with DVR (c) with
FLC (49 rules) (d) with FLC (25 rules) for LLLG fault
with linear load 76
4.7 Capacitor voltage for DVR (a) with PI (b) FLC (49
rules) and FLC (25 rules) with linear load 78
4.8 Voltage waveform (a) without DVR (b) injected
voltage (c) with DVR for LG fault with non-linear load 79
4.9 Voltage waveform (a) without DVR (b) injected
voltage (c) with DVR for LLG fault with non-linear
load
79
4.10 Voltage waveform (a) without DVR (b) injected
voltage (c) with DVR for LLLG fault with non-linear
load
80
4.11 Voltage THD (a) without DVR (b) with DVR (c) with
FLC (49 rules) (d) with FLC (25 rules) for LG fault
with non-linear load
81
4.12 Voltage THD (a) without DVR (b) with DVR (c) with
FLC (49 rules) (d) with FLC (25 rules) for LLG fault
with non-linear load
81
4.13 Voltage THD (a) without DVR (b) with DVR (c) with
FLC (49 rules) (d) with FLC (25 rules) for LLLG fault
with non-linear load
82
4.14 Capacitor voltage for DVR (a) with PI (b) FLC (49
rules) and FLC (25 rules) with non-linear load 83
4.15 Voltage waveform (a) without DVR (b) injected
voltage (c) with DVR for LG fault with FOC-IM load 84
4.16 Voltage waveform (a) without DVR (b) injected
voltage (c) with DVR for LLG fault with FOC-IM load 85
4.17 Voltage waveform (a) without DVR (b) injected
voltage (c) with DVR for LLLG fault with FOC-IM
load
85
4.18 Voltage THD (a) without DVR (b) with DVR (c) with
FLC (49 rules) (d) with FLC (25 rules) for LG fault
with FOC-IM load
86
4.19 Voltage THD (a) without DVR (b) with DVR (c) with
FLC (49 rules) (d) with FLC (25 rules) for LLG fault
with FOC-IM load
87
4.20 Voltage THD (a) without DVR (b) with DVR (c) with
FLC (49 rules) (d) with FLC (25 rules) for LLLG fault
with FOC-IM load
87
xv
4.21 Capacitor voltage for DVR (a) with PI (b) FLC (49
rules) and FLC (25 rules) with FOC-IM load 89
4.22 Voltage waveform (a) without UPQC (b) injected
voltage (c) with UPQC for LG fault with linear load 90
4.23 Voltage waveform (a) without UPQC (b) injected
voltage (c) with UPQC for LLG fault with linear load
91
4.24 Voltage waveform (a) without UPQC (b) injected
voltage (c) with UPQC for LLLG fault with linear load
91
4.25 Current waveform (a) without UPQC (b) injected
current (c) with UPQC for LG fault with linear load 92
4.26
Current waveform (a) without UPQC (b) injected
current (c) with UPQC for LLG fault with linear load
93
4.27 Current waveform (a) without UPQC (b) injected
current (c) with UPQC for LLLG fault with linear load
93
4.28 Voltage THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LG
fault with linear load
94
4.29 Voltage THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LLG
fault with linear load
95
4.30 Voltage THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LLLG
fault with linear load
95
4.31 Current THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LG
fault with linear load
97
4.32 Current THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LLG
fault with linear load
97
4.33 Current THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LLLG
fault with linear load
98
4.34 Capacitor voltage for UPQC (a) with PI (b) FLC (49
rules) and FLC (25 rules) with linear load
100
4.35 Capacitor current for UPQC (a) with PI (b) FLC (49
rules) and FLC (25 rules) with linear load 100
4.36 Voltage waveform (a) without UPQC (b) injected
voltage (c) with UPQC for LG fault with non-linear
load
101
4.37 Voltage waveform (a) without UPQC (b) injected
voltage (c) with UPQC for LLG fault with non-linear 102
xvi
load
4.38 Voltage waveform (a) without UPQC (b) injected
voltage (c) with UPQC for LLLG fault with non-linear
load
102
4.39 Current waveform (a) without UPQC (b) injected
current (c) with UPQC for LG fault with non-linear
load
103
4.40 Current waveform (a) without UPQC (b) injected
current (c) with UPQC for LLG fault with non-linear
load
104
4.41 Current waveform (a) without UPQC (b) injected
current (c) with UPQC for LLLG fault with non-linear
load
104
4.42 Voltage THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LG
fault with non-linear load
105
4.43 Voltage THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LLG
fault with non-linear load
106
4.44 Voltage THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LLLG
fault with non-linear load
106
4.45 Current THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LG
fault with non-linear load
108
4.46 Current THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LLG
fault with non-linear load
108
4.47 Current THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LLLG
fault with non-linear load
109
4.48 Capacitor voltage for UPQC (a) with PI (b) FLC (49
rules) and FLC (25 rules) with non-linear load 110
4.49 Capacitor current for UPQC (a) with PI (b) FLC (49
rules) and FLC (25 rules) with linear load 111
4.50 Voltage waveform (a) without UPQC (b) injected
voltage (c) with UPQC for LG fault with FOC-IM load 112
4.51 Voltage waveform (a) without UPQC (b) injected
voltage (c) with UPQC for LLG fault with FOC-IM
load
112
4.52 Voltage waveform (a) without UPQC (b) injected
voltage (c) with UPQC for LLLG fault with FOC-IM
load
113
xvii
4.53 Current waveform (a) without UPQC (b) injected
current (c) with UPQC for LG fault with FOC-IM load 114
4.54 Current waveform (a) without UPQC (b) injected
current (c) with UPQC for LLG fault with FOC-IM
load 114
4.55 Current waveform (a) without UPQC (b) injected
current (c) with UPQC for LLLG fault with FOC-IM
load
115
4.56 Voltage THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LG
fault with FOC-IM load
116
4.57 Voltage THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LG
fault with FOC-IM load
116
4.58 Voltage THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LLLG
fault with FOC-IM load
117
4.59 Current THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LG
fault with FOC-IM load
119
4.60 Current THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LLG
fault with FOC-IM load
119
4.61 Current THD (a) without UPQC (b) with UPQC (c)
with FLC (49 rules) (d) with FLC (25 rules) for LLLG
fault with FOC-IM load
120
4.62 Capacitor voltage for UPQC (a) with PI (b) FLC (49
rules) and FLC (25 rules) with FOC-IM load 122
4.63 Capacitor current for UPQC (a) with PI (b) FLC (49
rules) and FLC (25 rules) with FOC-IM load 122
LIST OF ABREVIATIONS
xviii
ANFIS - Adaptive Neuro-Fuzzy Inference System
ANN
- Artificial Neural Netwok
APF - Active Power Filters
CPD - Custom Power Devices
SCD - Synchronous Current Detection
CSI - Current Source Inverter
d - direct or real
DC - Direct Current
DFT - Discrete Fourier Transform
DOL - Direct-On-Line
d-q-0 - transformation direct-quadrature-zero transformation
DSTATCOM - Distribution STATic COMpensator
DVR - Dynamic Voltage Restorer
DWT - Discrete Wavelet Transform
EMI - Electro-Magnetic Interference filter
FACTS - Flexible AC Transmission Systems
FFT - Fast Fourier Transformer
FL - Fuzzy Logic
FLC - Fuzzy Logic Controller
FOC-IM - Field-Oriented Control Induction Motor
FORTRAN - FORula TRANslating System programming language
FT - Fourier Transform
GTO - Gate Turn Off thyristor
ICC - Indirect Current Control
IEEE - Institute of Electrical and Electronic Engineers
IGBT - Insulated-Gate Bipolar Transistor
IGCT - Integrated Gate-Commutated Thyristor
Ki - integral
Kp - proportional
LLG - Double Line-to-Ground fault
LLLG - Triple Line-to-Ground fault
LPF - Low Pass Filter
LQR - Linear Quadratic Regulator
xix
max-min - maximum-minimum
MC-DVR - Multi Converter DVR
MRA - Multi-Resolution Analysis
MSPWM - Multiple Sinusoidal Pulse Width Modulation
MVAr - Mega Volt Ampere reactive
NB - Negative Big
NM - Negative Medium
NS - Negative Small
OCC - One Cycle Control
OCCC - One Cycle Current Control
OPC - Optimal Predictive Control
PBT - Power Balance Theory
PCC - Point of Common Coupling
PI - Proportional Integral
PID - Proportional Integral Derivative
PL - Positive Large
PLL - Phase-Locked Loop
PM - Positive Medium
PQ - Power Quality
PR - Proportional Resonant
PS - Positive Small
PSCAD - Power System Computer Aided Design
PS-SPWM - Phase-Shifted Sinusoidal Pulse Width Modulation
PV - Photo-Voltaic
PWM - Pulse Width Modulation
Ref - Reference
RMS - Root Mean Square
SLG - Single Line-to-Ground fault
SPWM - Sinusoidal Pulse Width Modulation
SRF - Synchronous Reference Frame
SVM - Space Vector Modulation
THD - Total Harmonic Distortion
UCES - Ultra-Capacitor Energy Storage
xx
UPQC - Unified Power Quality Conditioner
UVT - Unit Vector Template generation
VAr - Volt Ampere reactive
VSC - Voltage Source Converter
VSI - Voltage Source Inverter
Z - Zero
ZSI - Z-Source Inverter
xxi
LIST OF SYMBOLS
A - Ampere
ce - Change in error
H - Henry
e - error
I - Current
IL - Load Current
kV - kiloVolt
kW - kiloWatt
L - Inductance
p.u - Per unit
R - Resistance
V - Voltage
VL - Load voltage
Vth - Thevenin equivalent system voltage during fault
X - Inductance
X/R - ratio of total inductive reactance to its total
resistance
Y - Star
Z - Impedance
Zth - Thevenin equivalent load Impedance
α - Alpha
β - Beta
Δ - Delta
δ - Sigma
μ - Micro
π - Pi
ω - Omega
xxii
LIST OF APPENDICES
APPENDIX TITLE PAGE
A1 IEEE Std. 1100-1992 Recommended Practice for
Powering and Grounding Electronic Equipment
144
A2 IEEE 519-1192 “Recommended practices and
requirements for Harmonic control” for voltage
145
A3 IEEE 519-1192 “Recommended practices and
requirements for Harmonic control” for current
146
A4 IEEE 1159-1995 “Recommended Practice for
Monitoring Electric PQ” for time domain duration
147
A5 IEEE 1159-1995 “Recommended Practice for
Monitoring Electric PQ” for magnitude deviation
148
B1
Matlab / Simulink function for memory space for
DVR and UPQC
149
B2
Matlab / Simulink function for computational time
for DVR and UPQC
150
C1
Further authentication of the results produced by
Matlab / Simulink function for memory space using
task manager (for DVR and UPQC)
151
CHAPTER 1
INTRODUCTION
1.1 Background of Study
Contemporary power system is an arrangement of composite networks
involving various generating stations and load centers integrated through extensive
transmission and distribution networks. Power supply interruptions and outages are a
nuisance affecting domestic, commercial and in particular industrial customers. This
results in considerable financial losses with high impact on production costs. In the
present competitive world market, dispersed generation trends and general awareness
of the people towards better quality of power have forced the restructuring of power
systems. Expectations on improved quality and reliability of power supply to the
customers have increased.Power Quality (PQ) is defined in IEEE Std book Electrical
Power System Quality (Dugan, et al., 1996) as “the concept of powering and
grounding sensitive electronic equipment in a manner suitable for the equipment”
(Reid, 1996). This phenomenon incorporates all possible situations in which power
system supply voltage (voltage quality) or load current (current quality) waveforms
deviate from sinusoidal waveform. PQ is a criterion for proper electrical system to
function efficiently without compromising the performance (Singh and Dwivedi,
2012).
PQ problems encompass severe disturbances such as voltage sag, voltage
swell, current and voltage harmonics, and unbalanced load. Inferior PQ leads to low
2
power factor and low efficiency, generating large current unbalance. PQ disturbances
may be either caused by the quality of the supply voltage (source) or by the quality
of the current drawn by the load. Advanced power electronic devices and equipments
widely employed nowadays draw harmonic currents and reactive power from AC
mains due to their inherent non-linear V-I characteristics. Such non-linear loads
pollute the network by injecting current harmonics. This consequently deteriorates
utility voltage and causes a drop in supply voltage and amplifies losses.
Considerable attention has been given to PQ due tomodern industrial shift
towards mechanized automation. This inclination trend relies heavily on sensitive
power electronic devices. These devices are much more susceptible to distortion in
supply voltage than their previous generation counterparts. This has caused
complications not only for the utilities but also for the end-users themselves. Modern
power semiconductor devices are in all likelihood not only the prime source of
harmonic insertion but also augment reactive power in the system. Rigorous
utilization of power converters as rectifiers creates non-sinusoidal current thus
polluting the supply. Consequently, the harmonic components will contaminate
voltage at the point of common coupling. Besides, these polluted voltages and
currents proliferate into the supply system, amplify losses, cause measurement
imprecision and create severe electromagnetic compatibility problems. Introduction
of system harmonics have brought PQ issues to the fore-front and compelled
suffering utilities to provide distortion-free sinusoidal power supply. At the same
time customers are also bound by regulations through proper standards to curb the
quantity of harmonic currents and unbalance in all the three phases due to different
loading conditions which augments harmonic distortions that a load may produce.
The situation calls for alleviation of PQ issues in the shape of “Custom Power
Devices (CPD)” which are capable enough to present customized resolution to PQ
problems. CPD improve the quality and reliability of power delivered to customers
and are based on electronic power converters and provide the ability to make quick
adjustments to control the electrical system. The strength and benefits of these
devices become diverse, when they are combined and this concept leads to the
evolution of multi-type CPD. The function of CPD is not only to minimize the
3
effects of voltage sag and swell, but also to limit the harmonic distortion caused by
the presence of non- linear loads in the network (Ghosh and Ledwich, 2001;
Khadkikar and Chandra, 2008; Renuga, et al., 2013).
Current harmonics are considered as the most frequent PQ issues while
voltage sag is the most detrimental. These problems incur huge financial losses.
Research reveals that voltage sag/swells and harmonic distortions at the Point of
Common Coupling (PCC) are mainly liable to severe impact on sensitive loads. Even
worse case scenario is the malfunctioning of system equipments (Kolhatkar and Das,
2007; Hari, et al., 2011; Khadkikar, 2013).
To reduce such unwanted nuisances, passive power filters were primarily
used. Well-designed passive filters can be implemented in large sizes of MVAr
ratings and provide almost maintenance free service due to absence of rotating parts.
These filters are more economical to implement than their rotating counterparts i.e.,
synchronous condensers. A fast response time of the order of one cycle or less can be
obtained. These compensation equipments have some drawbacks as they are not
suitable for variable loads, since, they are designed for a specific reactive power as
well as variation of the load impedance can detune the filter. To overcome passive
power filters characteristic limitations such as producing superfluous resonance and
augmenting harmonic currents, a step further in fruitful research efforts bore the
development and manifestation of more advanced Active Power Filters (APF)
technology. These however are presently very uneconomical but their installation
proves indispensable for solving PQ problems in distribution networks such as
compensation of harmonic current, reactive current and voltage sag. Ultimately, this
would ensure a pollution free system with increased reliability and quality. APF
family include different devices commonly called CPD. The concept of custom
power was introduced by (N.G. Hingorani) in 1995. This term illustrates the value-
added power that electric utilities will present to their customers. The enhanced level
of power consistency with minimal interruptions and less discrepancy will be
guaranteed by the application of power electronic controllers either to the utility
distribution systems or at the supply end of industrial and commercial customers.
CPD are the proficiently progressive face of APF family and are pertinent to power
4
distribution systems for accomplishing stability and reliability of power supply to a
large extent. Fundamentally, APF inject harmonic currents of the same magnitude
but opposite polarity to cancel harmonics. Nevertheless harmonic distortions are only
part of the problem, while fault or load variations may cause voltage sag. CPD
comprise of DSTATCOM (Distribution STAtic COMpensator), DVR (Dynamic
voltage restorer) and Unified Power Quality Conditioner (UPQC) etc. DSTATCOM
is connected in shunt with the power system whereas DVR is a series connected
device that injects series voltage to recompense supply voltage.DVR is recognized as
the most appropriate to protect sensitive loads against PQ disturbances. DVR role is
not only voltage sag mitigation but also harmonic distortion reduction caused by
non-linear loads in the network.
UPQC is the more advanced type of CPD combining two APFs. It’s good
control methods with precise recognition of the disturbance signal, swift processing
of reference signal and high dynamic response facilitates in preferred compensation.
It charters two voltage source inverters (VSI): one act as a series APF (DVR) and the
other as shunt APF (D-STATCOM), connected back to back through common DC-
link capacitor. The former is regarded as the most fitting to prevail over voltage
related problems while the latter as the most promising to manage current related
problems. Practical implementation of such devices emerges feasible, given that
superior quality supply voltage and drawn current is stressed profoundly.
Nevertheless, simultaneous installation of both DVR and DSTATCOM may not be a
worthwhile solution. Their combined configuration with back-to-back inverter
system called UPQC was proposed by Fujita and Akagi (Fujita and Akagi, 1995).
UPQC is ever since popularly used enormously and regarded as the ultimate solution
for inferior PQ predicament by several researches (Sadaiappan, et al., 2010; Hari, et
al., 2011).
UPQC is probably the best CPD dealing with both load current and supply
voltage imperfections. It consists of two VSI sharing the same capacitive DC-link. It
is a very versatile device that can perform both the functions of load compensation
and voltage control simultaneously.
5
1.2 Problem Statement
Inadequacy of conventional PQ improvement equipment has necessitated
vibrant and adaptable resolution to PQ problems. This has propelled the development
of CPD. The contemporary and promising CPD that deals with voltage related issues
is DVR, while the more flexible CPD is UPQC which deals mutually with load
current and supply voltage imperfections. Various researches have been performed in
relation to their performances under a variety of fault conditions with different
conventional linear and non-linear control systems with the application of linear,
non-linear and heavy loads. To be regarded as established equipments their
performances ought to be scrutinized further with different control strategies for
frequently utilized load conditions under frequently occurring fault conditions in the
distribution system. This needs modelling and development of both the equipments
along with their control schemes and algorithms for PQ improvement. Fuzzy Logic
Control (FLC) has gained momentum during the last decade or so especially in
power systems because it neither requires precise mathematical formulations nor fast
processors. Besides it needs less data storage in the form of knowledge base which
includes Membership Functions (MF’s) and rules.
Conventionally, the more advanced non-linear FLC system has been utilized
with 49 rules which are computationally demanding and time consuming. As the
number of the linguistic variables increases, the computational time and required
memory increase. This is because the implementation of FLC require a large
computational time for processing each step time in order to compute the appropriate
control value to be applied to the system. Therefore, a reduction of the large fuzzy
rule base is required. Although some studies have tried lesser rules (even 9 rules) but
they cannot come up with conclusive performance of the equipments. An effort is
needed to come up with the best possible number of rules for FLC system so that
both DVR and UPQC can perform satisfactorily, conforming to IEEE laid standards
for both harmonic compensation and voltage sag minimization and hence results in
enhanced PQ. Studies showed that FLC with 49 rules takes double computational
time as compared to FL with 25 rules (Karakose and Akin, 2010). Rule reduction
will definitely lessen computation effort and reduce time consumption for
6
processing. Performance analysis and comparison of this reduced rule control
strategy with classical PI and FLC with 49 rules for further evidence is necessitated
under harmonic generating loads including Field Oriented Control-Induction Motor
(FOC-IM) under frequently occurring fault conditions.
1.3 Objectives of the Research
The objectives of this research are as follows:
i) To develop simulation models of DVR and UPQC in distribution system
subject to the presence of voltage sag and harmonics with various load
and fault conditions.
ii) To design PI, FLC (49 rules) and FLC (25 rules) systems for DVR and
UPQC to tackle voltage sag and harmonic problems in distribution
network.
iii) To investigate effectiveness of PI, FLC (49 rules) and FLC (25 rules)
based DVR and UPQC and tuning and normalization of FLC (25 rules) to
get similar or better performance in accordance with the IEEE 519-1159
standards.
1.4 Scopes of the Research
The scopes of this research are shown below:
i) The system is a distribution network comprising of two 11 kV adjacent
feeders
7
ii) Performance of the designed models of DVR and UPQC is evaluated for
mitigating PQ issues such as voltage sag/swell and harmonic distortions.
iii) Performance of DVR and UPQC is investigated using PI control and FLC
under linear, non-linear and FOC-IM load conditions.
1.5 Significances of the Research
Significances of this research are:
i) Develop FLC knowledge base which includes MF’s and rules suitable for
proper functioning of DVR and UPQC. The increasing need is to design
highly reliable, efficient and low complexity controllers. FLC’s are able
to make effective decisions on the basis of linguistic information. The
application of FLC will definitely not only minimize computation efforts
but also improve performance of these equipments in relation to voltage
sag and harmonic mitigation.
ii) Formulate the best possible control strategy for DVR and UPQC which
will help improve PQ of the system with different load and fault
conditions. Amongst the three control strategies which are PI, FLC with
49 rules and reduced25 rules the focus will be on FLC method with 25
rules. Although, many works have been reported in literature regarding
reduction of rules at the expense of enhanced complexities. The easier
approach of tuning of parameters as well as scaling factors and
normalization help excel the performance of this strategy as compared to
PI control method. As compared to FLC 49 rules its performance will be
improved as well as reduction in the computation time and memory space
with the exception of a few results.
8
1.6 Organization of Thesis
Contents of the thesis are arranged as follows.
Chapter 2 defines the different terms and concepts associated with PQ and
CPD. Literature survey is also included in this chapter.
Chapter 3 explains in detail the methodology adopted in this work. Various
control strategies employed for both DVR and UPQC are taken into consideration to
improve PQ.
Chapter 4 presents discussion of the results of PI, FLC (49 rules) and FLC
(25 rules) control strategies for DVR and UPQC Matlab / Simulink test models.
Chapter 5 summarizes the conclusion of this work and future work of this
research.
136
REFERENCES
Ajay Daniel, J., Gopinath, C. and Ramesh, R. (2013). Z-source inverter based DVR
using super capacitor to mitigate voltage sag and voltage swell. International
Conference on Circuits, Power and Computing Technologies (ICCPCT). 37-
42.
Ali, S., Chauhan, Y. K. and Kumar, B. (2013). Study and performance of DVR for
voltage quality enhancement. International Conference on Energy Efficient
Technologies for Sustainability (ICEETS). 983-988.
Axente, I., Basu, M. and Conlon, M. F. (2011). DC-link voltage control of UPQC for
better dynamic performance. Electric Power Systems Research. 81, 1815-
1824.
Azim, M. R. and Hoque, M. A. (2011). A fuzzy logic based DVR for voltage sag and
swell mitigation for industrial induction motor loads. International Journal of
Computer Applications. 30 (8), 9-18.
Banaei, M., Dehghanzadeh, A., Salary, E., Khounjahan, H. and Alizadeh, R. (2012).
Z-source-based multilevel inverter with reduction of switches. Institution of
Engineering and Technology Power Electronics. 5 (3), 385-392.
Banaei, M. R. and Dehghanzadeh, A. R. (2010). A novel Z-source based multilevel
inverter for renewable sources fed DVR. Power Quality Conference (PQC).1-
6.
Bangar, A. and Nijhawan, P. (2011). Role of dynamic voltage restorer against
voltage dip with induction motor as load. Internation Journal of Electrical
engineering. 4 (5), 617-624.
Barros, J. D. and Silva, J. (2010). Multilevel optimal predictive dynamic voltage
restorer. IEEE Transactions on Industrial Electronics. 57 (8), 2747-2760.
Benachaiba, C. and Ferdi, B. (2008). Voltage quality improvement using DVR.
Electrical Power Quality and Utilization Journal. 14 (1), 39-46.
137
Chankhamrian, W. and Bhumkittipich, K. (2011). The effect of series-connected
transformer in DVR applications. Energy Procedia. 9, 306-315.
Chellammal, N., Dash, S. S., Velmurugan, V. and Gurram, R. (2012). Power quality
improvement using multilevel inverter as series active filter. International
Conference on Emerging Trends in Science, Engineering and Technology
(INCOSET). 450-455.
Dib, S., Ferdi, B. and Benachaiba, C. (2011). Adaptive neuro-fuzzy inference system
based DVR controller design. Leonardo Electronic Journal of Practices and
Technologies. 18, 49-64.
Dinesh, L., Rao, S. S. and Rao, N. S. M. (2012). Simulation of unified power quality
conditioner for power quality improvement using fuzzy logic and neural
networks. Innovative Systems Design and Engineering. 3 (3), 36-46.
Dugan, R. C., McGranaghan, M. F and Beaty, H. W. Electrical Power System
Quality. New York: McGraw-Hill | c 1996.
ElShennawy, T. I. and Yehia, A. (2011). Dynamic voltage restorer for voltage sag
mitigation. International Journal on Electrical Engineering and Informatics.
3, 1-11.
Fatiha, M., Mohamed, M. and Nadia, A. A. (2011). New hysteresis control band of
an unified power quality conditioner. Electric Power Systems Research. 81,
1743-1753.
Ferdi, B., Benachaiba, C., Dib, S. and Dehini, R. (2010). Adaptive PI control of
dynamic voltage restorer using fuzzy logic. Journal of Electrical
Engineering. Theory and Application. 1 (3), 165-173.
Ferdi, B., Benachaiba, C., Berbaoui, B. and Dehini, R. (2012). DC-link voltage
control of unified power quality conditioner using PI fuzzy self-tuning
controller. Journal of Electrical & Electronics Engineering. 5 (1), 57-62.
Forghani, M. and Afsharnia, S. (2007). Online wavelet transform-based control
strategy for UPQC control system. IEEE Transactions on Power Delivery. 22
(1), 481-491.
Fujita, H. and Akagi, H. (1995). A new Power Line Conditioner for Harmonic
Compensation in Power Systems. IEEE Transactions on Power Delivery. 10
(3), 1570-1575.
Geethalakshmi, B. and Sharmiladevy, C. (2012). An improvement in the
performance of unified power quality conditioner using DC-link voltage
138
control. International Conference on Advances in Engineering, Science and
Management (ICAESM). 534-539.
Ghosh, A., Jindal, A. K. and Joshi, A. (2004). Design of a capacitor-supported DVR
for unbalanced and distorted loads. IEEE Transactions on Power Delivery. 19
(1), 405-413.
Ghosh, A. and Ledwich, G. (2001). A unified power quality conditioner for
simultaneous voltage and current compensation. Electric power systems
research 59, 55-63.
Ghosh, H., Kumar Saha, P. and Kumar Panda, G. (2012). Performance comparison
between DVR and DSTATCOM used for load voltage control in distribution
side. International Conference on Advances in Power Conversion and Energy
Technologies (APCET). 1-6.
Guo, W., Xiao, L. and Dai, S. (2013). Control and design of a current source united
power quality conditioner with fault current limiting ability. IET Power
Electronics. 6 (2), 297-308.
Hari, N., Vijayakumar, K. and Dash, S. S. (2011). A versatile control scheme for
UPQC for power quality improvement. International Conference on
Emerging Trends in Electrical and Computer Technology (ICETECT). 453-
458.
Hilloowala, R. M. and Sharaf, A. K. (1996). A rule-based fuzzy logic controller for a
PWM inverter in a stand alone wing energy conversion scheme. IEEE
Transactions on Industry Application. 32 (1), 57-65.
Ise, T., Hayashi, Y. and Tsuji, K. (2000). Definitions of power quality levels and the
simplest approach for unbundled power quality services. IEEE Ninth
International Conference on Harmonics and Quality of Power Proceedings.
385-390.
Jain, S., Thakur, S. S. and Phulambrikar, S. P. (2012). Fuzzy controller based DVR
to mitigate power quality and reduce the harmonic distortion of sensitive
load. International Journal of Advanced Research in Electrical, Electronics
and Intrumantation Engineering. 1 (5), 351-361.
139
Jowder, F. (2009). Design and analysis of dynamic voltage restorer for deep voltage
sag and harmonic compensation. IET Generation, Transmission &
Distribution. 3 (6), 547-560.
Jurado, F., Valverde, M. and Carpio, J. (2003). Voltage sag correction by dynamic
voltage restorer based on fuzzy logic control. Canadian Conference on
Electrical and Computer Engineering (CCECE). 421-424.
Kaliappan, S., Poornima, M. and Rajeswari, R. (2013). Improvement of source
voltage and load current harmonic mitigation using UPQC: 7th International
Conference on a survey. Intelligent Systems and Control (ISCO). 110-114.
Kanjiya, P., Singh, B., Chandra, A. and Al-Haddad, K. (2013). “SRF theory
revisited” to control self-supported dynamic voltage restorer for unbalanced
and nonlinear loads. IEEE Transactions on Industry Applications. 49 (5),
2330-2340.
Karanki, K., Geddada, G., Mishra, M. K. and Kumar, B. (2013). A modified three-
phase four-wire UPQC topology with reduced DC-link voltage rating. IEEE
Transactions on Industrial Electronics. 60 (9), 3555-3566.
Karakose, M. and E. Akin (2010). Block based fuzzy controllers. International
Journal of Research & Reviews in Applied Sciences. 3(1), 100-110.
Kesler, M. and Ozdemir, E. (2011). Synchronous-reference-frame-based control
method for UPQC under unbalanced and distorted load conditions. IEEE
Transactions on Industrial Electronics. 58(9), 3967-3975.
Khadkikar, V. (2013). Fixed and variable power angle control methods for unified
power quality conditioner: operation, control and impact assessment on shunt
and series inverter kVA loadings. Institution of Engineering and Technology
Power Electronics. 6 (7), 1299-1307.
Khadkikar, V. and Chandra, A. (2008). A new control philosophy for a unified
power quality conditioner to coordinate load-reactive power demand between
shunt and series inverters. IEEE Transactions on Power Delivery. 23 (4),
2522-2534.
Khadkikar, V., Chandra, A., Barry, A. and Nguyen, T. (2011). Power quality
enhancement utilising single-phase unified power quality conditioner: digital
signal processor-based experimental validation. Institution of Engineering
and Technology Power Electronics. 4 (3), 323-331.
140
Khanh, B. Q., Lian, J., Ramachandran, B., Srivastava, S. and Cartes, D. (2012).
Mitigating voltage sags due to DOL starting of three phase asynchronous
motors using dynamic voltage restorer. Transmission and Distribution
Conference and Exposition. 1-8.
Kinhal, V. G., Agarwal, P. and Gupta, H. O. (2011). Performance investigation of
neural-network-based unified power-quality conditioner. IEEE Transactions
on Power Delivery. 26(1), 431-437.
Kolhatkar, Y. Y. and Das, S. P. (2007). Experimental investigation of a single-phase
UPQC with minimum VA loading. IEEE Transactions on Power Delivery. 22
(1), 373-380.
Kumar, K. R. and Sastry, S. (2011). Application of PI, fuzzy logic and ANN in
improvement of power quality using UPQC. Elixir International Journal. 38,
4465-4468.
Kumari, P. and Garg, V. K. (2013). Simulation of dynamic voltage restorer using
Matlab to enhance power quality in distribution system. International Journal
of Engineering Research and Applications (IJERA), 3(4), 1436-1441.
Laxmi, A. J., Das, G. T. R. and Rao, K. U. (2007). Role of PI and fuzzy controllers
in unified power quality conditioner. ARPN Journal of Engineering and
Applied Sciences, 2 (2), 1-10.
Lee, D. M., Habetler, T. G., Harley, R. G., Keister, T. L. and Rostron, J. R. (2007). A
voltage sag supporter utilizing a PWM-switched autotransformer. IEEE
Transactions on Power Electronics. 22 (2), 626-635.
Lozano, J. M., Ramirez, J. M. and Correa, R. E. (2010). A novel dynamic voltage
restorer based on matrix converters. Proceedings of the International
Symposium of Modern Electric Power Systems (MEPS). 1-7.
Mai, J. and Swarupa, V. (2013). Generalized UPQC system with an improved control
method using PV array for reduction of harmonics. International Journal of
Innovative Research and Development. 2(8), 326-333. .
Mandakini, P., Ravichandrudu, K., Babu, M. P. Y. and Anjaneyulu, M. G. A. (2013).
Noval approach for a ameliorationof quality power managementby a custom
power device. International Journal of Science, Environment and
Technology. 2(5), 969-980.
141
Merabet, L., Saad, S., Abdeslam, D. O. and Omeiri, A. (2013). A comparative study
of harmonic currents extraction by simulation and implementation.
International Journal of Electrical Power and Energy Systems. 53, 507-514.
Mohammed, S. A. and Abdel-Moamen, M. A. (2013). Fuzzy logic controller based
dynamic voltage restorer as voltage sag restore and harmonic compensator.
International Journal of Control, Automationand Systems. 2(3), 53-57.
Naidu, P. and Raja, B. (2011). A new proposal for voltage regulation multi feeders /
multibus systems using MC-DVR. International Conference on Power and
Energy Systems (ICPS). 1-8.
Padmanaban, P. A. and Marimuthu, M. R. (2012). Fuzzy logic based UPQC for
compensating power quality problems. Australian Journal of Basic and
Applied Sciences. 6 (7), 167-178.
Pal, Y., Swarup, A. and Singh, B. (2013). New control algorithms for three-phase
four-wire unified power quality conditioner—a simulation study. Journal of
Electrical Power Quality and Utilisation. 16 (1), 1-10.
Pramila, E. (2014). Unified power quality conditioner for power quality
improvement using ultra-capacitor energy storage. Internation Journal of
Emerging Trends in Engineering and Development. 4 (1), 134-142.
Ramasamy, M. and Thangavel, S. (2011). Photovoltaic based dynamic voltage
restorer with outage handling capability using PI controller. Energy Procedia.
12, 560-569.
Ramya, P. and Bhavani, J. (2013). Different controllers of UPQC for power quality
evolution. International Journal of Current Engineering and Technology. 3
(5), 1733-1738.
Rao, M. R. R. and Dash, S. S. (2011). Design of UPQC with Minimization of DC-
link voltage for the improvement of power quality by fuzzy logic controller.
ACEEE International Journal on Electrical and Power Engineering, 2 (1),
36-42.
Rao, R. R. and Dash, S. S. (2010). Enhancement of power quality by using unified
power quality conditioner with PID and fuzzy logic controller. International
Journal of Computer Applications. 5 (7), 21-27.
Raokhande, D. L., Mujawar, I. I., Mujawar, I. I., Patil, D. and Gudaru, U. (2014). A
new strategy of series-shunt power quality compensator. International
142
Journal of Innovative Research in Electrical, Electronics, Instrumentation
and Control Engineering. 2 (1), 523-529.
Raokhande, D. L., Patil, D. and Gudaru, U. (2013). Performance of series-shunt
power quality compensator under unbalanced and distorted loading
conditions. IEEE International Conference on Control Applications (CCA).
1147-1152.
Ravichandrudu, K., Devi, D. S. and Babu, P. Y. (2013). Mitigation of power system
disturbance by using MC-UPQC with PI, ANN and Fuzzy controller
technique. International Journal of Application or Innovation in Engineering
and Management. 2 (10), 101-112.
Reid, W. E. (1996). Power quality issues-standards and guidelines. IEEE
Transactions on Industry Applications. 32 (3), 625-632.
Roncero-Sánchez, P., Acha, E., Ortega-Calderon, J. E., Feliu, V. and García-Cerrada,
A. (2009). A versatile control scheme for a dynamic voltage restorer for
power-quality improvement. IEEE Transactions on Power Delivery. 24 (1),
277-284.
Rong, Y., Li, C. and Ding, Q. (2009). An adaptive harmonic detection and a novel
current control strategy for unified power quality conditioner. Simulation
Modelling Practice and Theory, 17, 955-966.
Sadaiappan, S., Renuga, P. and Kavitha, D. (2010). Modeling and simulation of
series compensator to mitigate power quality problems. International Journal
of Engineering, Science and Technology. 2 (12), 7385-7394.
Sannino, A., Svensson, J. and Larsson, T. (2003). Power-electronic solutions to
power quality problems. Electric Power Systems Research. 66, 71-82.
Shen, K., Wang, J., Gao, Z., Cai, X. and Ji, Y. (2010). Dynamic voltage restorer
based on proportional-resonant control. Asia Pacific Power and Energy
Engineering Conference (APPEEC). 1-4.
Singh, A., Arora, P. and Singh, B. (2013). Voltage sag mitigation by fuzzy controlled
DVR. International Journal of Advanced Electrical and Electronics
Engineering 2 (6), 93-100.
Singh, B., Jayaprakash, P., Kothari, D. and Chandra, A. (2008). Indirect control of
capacitor supported DVR for power quality improvement in distribution
system. Power and Energy Society General Meeting-Conversion and
Delivery of Electrical Energy in the 21st Century. 1-7.
143
Singh, K. K. and Dwivedi, J. (2012). Performance study of unified power quality
conditioner using Matlab Simulink. International Journal of Scientific and
Technology Research. 1 (11), 27-31.
Srinath, S., Kumar, C. and Selvan, M. (2012). Digital feedback control based
dynamic voltage compensator for voltage sag mitigation: Simulation and
experimental validation. International Conference onIndustrial and
Information Systems (ICIIS). 1-6.
Srivastava, A., Dixit, R. and Dwivedi, J. K. (2013). Problems in supply system and
method of improvement of power quality. International Journal of Latest
research in science and technology. 2 (2), 157-162.
Srivastava, A., Dixit, R. and Pandey, A. K. (2013). Method of improving voltage
quality using modern power electronics. International Journal of Emerging
Technology and Advanced Engineering. 3 (5), 197-203.
Suja, K. and Jacob Raglend, I. (2013). Fuzzy based unified power quality conditioner
for power quality improvement. International Conference on Circuits, Power
and Computing Technologies (ICCPCT). 49-52.
Teke, A., Bayindir, K. and Tümay, M. (2010). Fast sag / swell detection method for
fuzzy logic controlled dynamic voltage restorer. IET generation, transmission
and distribution. 4 (1), 1-12.
Teke, A., Saribulut, L. and Tumay, M. (2011). A novel reference signal generation
method for power-quality improvement of unified power-quality conditioner.
IEEE Transactions on Power Delivery. 26 (4), 2205-2214.
Tiwari, H. and Gupta, S. K. (2010). Dynamic voltage restorer based on load
condition. International journal of innovation, management and technology,
1 (1), 75-81.
Usha, R. P., Rajkumar, M. and Reddy, S. R. (2011). Voltage sag / swell
compensation using Z-Source inverter based dynamic voltage restorer.
International Conference on Emerging Trends in Electrical and Computer
Technology (ICETECT). 268-273.
Varalakshmi, M. K. and Geragani, M. S. (2013). Enhancement of power quality by
using UPQC system with comparison of PI and fuzzy control methods under
distorted and unbalanced load conditions. International Journal of
Engineering Research and Technology. 2 (11), 3472-3484.
144
Vilathgamuwa, M., Perera, A. R. and Choi, S. (2002). Performance improvement of
the dynamic voltage restorer with closed-loop load voltage and current-mode
control. IEEE Transactions on Power Electronics. 17 (5), 824-834.
Wu, D. and Chang, C. (2011). Voltage sag mitigation in offshore oil rig power
system by dynamic voltage restorer. International Symposium on Industrial
Electronics (ISIE). 1160-1165.