table of contents -...

viii

TABLE OF CONTENTS

CHAPTER NO. TITLE PAGE NO.

ABSTRACT iii

LIST OF TABLES xvi

LIST OF FIGURES xvi

LIST OF ABBREVIATIONS xxvi

1 INTRODUCTION 1

1.1 MODERN POWER SYSTEM REQUIREMENTS 1

1.2 POWER FLOW CONTROL

IN TRANSMISSION LINES 4

1.3 NEED FOR REACTIVE POWER

COMPENSATION 7

1.4 LITERATURE SURVEY 9

1.5 POWER FLOW CONTROL THROUGH

SHUNT REACTIVE POWER

COMPENSATOR - STATCOM 14

1.6 STRUCTURE OF THE THESIS 18

1.7 CONCLUSION 19

2 CONVENTIONAL STATCOM 20

2.1 COMPENSATION PRINCIPLE OF STATCOM 20

2.1.2 Power Exchange in STATCOM

Application 23

2.2 STATCOM CONTROL STRATEGY 27

2.2.1 Conventional PWM Control Technique 29

ix


2.3 INTERPOLATION FIRING

CONTROL SCHEME 31

2.3.1 Generation of Interpolation Firing Pulses 31

2.4 STATCOM MODELING 33

2.4.1 STATCOM Transient Stability Model 36

2.4.2 STATCOM Steady State Model 38

2.4.3 Dynamic d-q Modeling of STATCOM 40

2.5 MITIGATION TECHNIQUE REALIZATION

IN PSCAD/ EMTDC 44

2.5.1 STATCOM Control in Simulation Program 45

2.5.2 Interpolation Firing Circuit 48

2.6 IMPLEMENTATION OF VSC

BASED STATCOM IN PSCAD 50

2.7 DISCUSSION ON RESULTS 53

2.8 CONCLUSION 55

3 CASCADED MULTILEVEL INVERTERS 56

3.1 INTRODUCTION 56

3.2 TOPOLOGIES OF MULTILEVEL INVERTERS 59

3.2.1 Diode-Clamped Multilevel Converter 59

3.2.2 Flying-Capacitor Multilevel Converter 61

3.2.3 Cascaded-Multilevel Converters

with Separated DC Sources 63

3.2.4 Comparison of Power Component

Requirements among Multilevel Converters 66

3.2.5 Proposed Asymmetric Cascaded

Multilevel Converter 69

x


3.3 MODULATION STRATEGIES 70

3.3.1 Carrier based PWM 73

3.4 POWER FLOW SOLUTIONS 79

3.4.1 Switching Angle Calculation

using Newton-Raphson Method 80

3.5 PROPOSED MODULATION STRATEGY 84

3.5.1 Inverted Sine Carrier PWM Strategy 84

3.5.2 Proposed Variable Frequency

ISPWM Technique 86

3.6 IMPLEMENTATION OF ASYMMETRIC

MULTILEVEL INVERTER 87

3.6.1 Performance Evaluation of CMC

Employing Conventional PWM 90


Employing Unipolar ISCPWM 92


Employing VFISCPWM 98

3.7 NEURAL NETWORK CONTROL

OF ACMC 104

3.8 FPGA BASED HARDWARE

IMPLEMENTATION 108

3.8.1 Generation of Gating Pulses for

the Proposed PWM 111

3.9 CONCLUSION 114

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4 STABILITY ANALYSIS OF INDUCTION

GENERATORS USING STATCOM 116

4.1 RENEWABLE WIND POWER SUPPORT

IN THE POWER SYSTEM 116

4.2 WIND POWER INTEGRATION CHALLENGES 118

4.2.1 Low Voltage Ride Through

(LVRT) Capability 120

4.3 STABILITY ANALYSIS OF INDUCTION

GENERATOR BASED WIND TURBINES 121

4.3.1 Voltage Stabilization and Fluctuation

Mitigation 124

4.3.2 Electrical Modeling Issues and

Requirements of Fixed Speed

Induction Generators 127

4.4 WIND TURBINE MODEL 130

4.4.1 Mechanical Model 130

4.4.2 Dynamic dq Model 132

4.5 FACTS BASED SOLUTIONS 136

4.5.1 Proposed CMC based STATCOM 137

4.6 STEADY STATE VOLTAGE CONTROL

WITH STATCOM 139

4.7 PERFORMANCE EVALUATION OF VSC

BASED STATCOM 144

4.8 TEST SYSTEM WITH CMC

BASED STATCOM 147

4.8.1 Reactive Power Compensation using

5-level CMC based STATCOM 152

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4.9 COMPARISON OF RESULTS 153

4.10 PERFORMANCE EVALUATION

OF ACMC STATCOM 156

4.11 HARDWARE IMPLEMENTATION 163

4.12 CONCLUSION 165

5 ACTIVE POWER COMPENSATION

OF STATCOM WITH ENERGY

STORAGE SYSTEMS 167

5.1 INTRODUCTION 167

5.2 ENERGY STORAGE SYSTEM 168

5.2.1 Energy Storage using Capacitors 169

5.2.2 Energy Storage using Batteries 170

5.2.3 Energy Storage using SMES 171

5.2.4 Comparison between SMES and

other Energy Storage Devices 173

5.3 THE SMES SYSTEM AND ITS ROLE

IN POWER SYSTEMS 174

5.4 INTEGRATION OF SMES WITH A STATCOM 176

5.4.1 Active and Reactive Power Control 177

5.4.2 Control Scheme of STATCOM / SMES 179

5.4.3 ESS-Chopper Topology 182

5.4.4 Interface between ESS and the DC Link

of the VSC 188

5.5 CONVERTER CONTROL FOR ACTIVE

POWER EXCHANGE 191

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5.6 SIMULATION OF POWER SYSTEM

RESPONSE TO ACTIVE POWER

COMPENSATION 197

5.6.1 Integration of ESS with STATCOM 200

5.6.2 Simulation Results 201

5.7 LOCATION OF STATCOM 203

5.8 CONCLUSION 206

6 CONCLUSION AND FUTURE WORK 207

6.1 CONCLUSION 207

6.2 SCOPE FOR FUTURE RESEARCH 210

REFERENCES 211

LIST OF PUBLICATIONS 227

VITAE 229

xiv

LIST OF TABLES

TABLE

NO.TITLE

PAGE

NO.

3.1 Diode-clamped 5-level converter voltage levels

and their switch states 61

3.2 Flying capacitor 5-level voltage levels and

their corresponding switch states 63

3.3 CMC 5-level voltage levels and their corresponding

switch states 66

3.4 Comparison among multilevel converters based on

power component requirements for phase leg 67

3.5 Comparison of number of devices required per

phase 68

3.6 Switching angles for various modulation indexes 83

3.7 Switching sequence for 7-level ACMC 89

3.8 Comparison of unipolar ISCPWM with

conventional PWM 96

3.9 Comparison of THD values - VFISPWM

with unipolar ISPWM technique 103

3.10 Switching sequence 107

3.11 Comparison of HEM with conventional SPWM 108

4.1 Comparison of simulation results 151

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TABLE

NO.TITLE

PAGE

NO.

4.2 Comparison of results with 3-level and 5-level

STATCOM 156

5.1 Chopper switching signals sequence during

charging mode 186

5.2 Chopper switching signals sequence during

discharging mode 186

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LIST OF FIGURES

FIGURE

NO.TITLE

PAGE

NO.

1.1 Operational limits of the system for voltage

collapse 2

1.2 Equivalent circuit model 5

1.3 Power angle curve 5

1.4 Equivalent circuit of an AC power system with

compensator 7

1.5 Phasor diagram (uncompensated) 8

1.6 Phasor diagram (compensated for constant

voltage) 9

1.7 Power transmission characteristic with dynamic

shunt compensation 15

1.8 Mid-point compensation by STATCOM 16

1.9 P- characteristics with and without STATCOM 17

2.1 Functional model of a STATCOM 20

2.2 Single line diagram 21

2.3 Operating modes of STATCOM 24

2.4 STATCOM phasor diagrams 26

2.5 STATCOM phasor diagrams 27

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FIGURE

NO.TITLE

PAGE

NO.

2.6 Block diagram of a STATCOM with PWM

voltage control 30

2.7 Firing angle measurement with and

without interpolation 31

2.8 Equivalent circuit of STATCOM 34

2.9 Transient stability model of a STATCOM 37

2.10 Phasor diagram of a PWM converter 39

2.11 Three phase to two phase transformation 41

2.12 to d-q transformation 42

2.13 Functional model of the proposed system 44

2.14 Control scheme implemented in PSCAD /

EMTDC 45

2.15(a) Generation of triangular pulses 46

2.15(b) Generation of sine wave pulses 46

2.16 Logic and control blocks in interpolation 48

2.17 Interpolation firing component 49

2.18 Load voltage wave form without STATCOM 51

2.19 Load voltage wave form with STATCOM 51

2.20 Real power consumption without STATCOM 51

2.21 Real power consumption with STATCOM 52

2.22 Reactive power consumption with STATCOM 53

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FIGURE

NO.TITLE

PAGE

NO.

2.23 Reactive power consumption without STATCOM 52

2.24 Capacitor voltage wave form 53

2.25 Reactive power injected by STATCOM 53

3.1 One phase leg of an inverter 56

3.2 Power circuit of one phase leg of a 5-level

DCMLI 60

3.3 Power circuit of one phase leg of a 5-level FCMC 62

3.4(a) Single phase leg structure of a CMC with SDCS 64

3.4(b) Individual H-Bridge cell of a CMC 64

3.5 Switching modes of 5-level CMC 65

3.6 Asymmetric cascaded-multilevel converter 70

3.7 SPWM modulation 75

3.8 Multilevel SPWM with PS method in a 7-level

inverter 76

3.9 Generation of pulses using ISPWM 85

3.10 Asymmetric cascaded 7-level inverter 88

3.11 Simulation circuit for the generation of triangular

wave 90

3.12 Simulation circuit of conventional cascaded MLI 91

3.13 Triangular carrier waves 91

3.14 Triangular carrier and reference sine waveforms

for conventional PWM 91

3.15 Output voltage of CMC (Conventional PWM) 92

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FIGURE

NO.TITLE

PAGE

NO.

3.16 FFT Window for output voltage (Conventional

PWM) 92

3.17 Simulation circuit for the generation of unipolar

inverted sine carrier waves 93

3.18 Waves employed for generating inverted sine

waves 93

3.19 Unipolar inverted sine carrier waves 94

3.20 Inverted sine carrier waves (7-level) 94

3.21 Reference and inverted sine waveforms

for unipolar ISPWM 95

3.22 Output voltage of conventional 7-level CMC

employing Unipolar ISCPWM 95

3.23 FT window for output voltage (Unipolar ISPWM) 96

3.24 Output voltage waveform of single phase 7-level

ACMC 97

3.25 Output voltage waveform of three phase 7-level

ACMC (Unipolar ISCPWM) 97

3.26 Simulation circuit for the generation of variable

frequency inverted sine carrier waves 98

3.27 Carrier and inverted sine waveforms

for VFISCPWM technique 99

3.28 Variable frequency inverted sine carrier waves 99

3.29 Output voltage waveform of single phase 7-level

ACMC employing VFISCPWM 100

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FIGURE

NO.TITLE

PAGE

NO.

3.30 Output voltage waveform of three phase 7-level

ACMC 100

3.31 Output voltages waveform of three phase 7-level

ACMC 101

3.32 FFT window for output voltage (Unipolar

ISPWM) 101

3.33 FFT window for output voltage (VFISPWM) 102

3.34 Multiport system 105

3.35 ACMC Simulation circuit using ANN controller 105

3.36 ACMC simulation circuit using conventional

SPWM controller 106

3.37 Output voltage of the 7-level ACMC using ANN

controller 106

3.38 Block diagram of Spartan 3E-Xilinx (Xc3s500-

Fg320) 108

3.39 FPGA kit programmed with Xilinx ISE tool 109

3.40 FPGA kit (Spartan 3E-[Xc3s500-Fg320])

and two stage cascaded inverter 109

3.41 Generation of PWM pulses from FPGA 111

3.42 VLSI simulation : model SIM PWM Pulses 112

3.43 5-level output voltage waveform for ISCPWM

inverter 112

3.44 Generated pulses using ISPWM technique in

CRO 113

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FIGURE

NO.TITLE

PAGE

NO.

3.45 Cascaded 7-level inverter output waveform in

CRO 114

4.1 Voltage dip profile 117

4.2 Fixed-speed system with stall or active-stall

control 118

4.3 LVRT requirement for wind generation facilities 120

4.4 Fixed speed wind energy conversion system 122

4.5 CP - curves for different pitch angles 123

4.6 Single line diagram of a WECS 127

4.7 Equivalent circuit of an induction generator 128

4.8 Mechanical model for the wind turbine 130

4.9 dq model of wind turbine 132

4.10 CMC based topology 138

4.11 Block diagram for voltage control using

STATCOM 139

4.12 STATCOM control scheme 140

4.13 Simplified model of the CMC based STATCOM

in both abc and dqo coordinates 142

4.14 Reactive power absorbed by the induction

generator 145

4.15 Active power 146

4.16 Power factor 146

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FIGURE

NO.TITLE

PAGE

NO.

4.17 THD measurement 147

4.18 Single line diagram of the test system 148

4.19 Active power without STATCOM 148

4.20 Reactive power without STATCOM 149

4.21 Grid voltage without STATCOM 149

4.22 Load voltage without STATCOM 149

4.23 Active power with 3-level inverter STATCOM 150

4.24 Reactive power with 3-level inverter STATCOM 150

4.25 Grid voltage with 3-level inverter STATCOM 150

4.26 Load voltage with 3-level inverter STATCOM 151

4.27 Active power with cascaded 5-level inverter

STATCOM 152

4.28 Reactive power with cascaded 5-level inverter

STATCOM 152

4.29 Load voltage with cascaded 5-level inverter

STATCOM 153

4.30 Grid voltage with cascaded 5-level inverter

STATCOM 153

4.31 Comparison of grid active power 154

4.32 Comparison of grid reactive power 154

4.33 Comparison of load active power 154

4.34 Comparison of load reactive power 155

4.35 Comparison of wind farm active power 155

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FIGURE

NO.TITLE

PAGE

NO.

4.36 Comparison of wind farm reactive power 155

4.37 Generation of carrier signals 157

4.38 Switching signals using multicarrier based

SPWM 158

4.39 Load voltage profile 158

4.40 Load current waveforms 159

4.41 Real Power waveforms 160

4.42 Reactive power waveforms 160

4.43 Per phase voltage output of CMC 161

4.44 7-level voltage output of CMC 161

4.45 THD for 7-level CMC based STATCOM 162

4.46 THD for 9-level CMC based STATCOM 162

4.47 THD for 9-level ACMC based STATCOM 162

4.48 Hardware circuit implementation 163

4.49 Single H1 bridge output waveform in CRO 164

4.50 Single H2 bridge output waveform in CRO 164

4.51 Cascaded 5-level inverter output waveform in

CRO 165

5.1 Basic components of a SMES system 175

5.2 PCS for SMES-based FACTS devices 175

5.3 Integration of SMES with a STATCOM 176

5.4 STATCOM/SMES configuration 178

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FIGURE

NO.TITLE

PAGE

NO.

5.5 STATCOM/ESS output characteristics 179

5.6 Internal control block of the VSI and DC-DC

chopper 180

5.7 External control block of the STATCOM/SMES

system 181

5.8 DC-DC chopper topology 183

5.9 2-level two-quadrant DC-DC chopper 184

5.10 Sub topologies for the chopper 185

5.11 Chopper equivalent circuit 187

5.12 DC link regulator 189

5.13 24-pulse VSI 191

5.14(a) Single-phase equivalent circuit of a

STATCOM/ESS and utility System 192

5.14(b) Phasor diagram 192

5.15 V-I characteristics in different reference

co-ordinates 194

5.16 Cyclic load model 198

5.17 48-pulse voltage source inverter 199

5.18 STATCOM integration with SMES 200

5.19 Active power at sending end with and without

compensation 201

5.20 Reactive power at sending end with and without

compensation 201

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FIGURE

NO.TITLE

PAGE

NO.

5.21 Active power at receiving end with and without

compensation 202

5.22 Reactive power at receiving end with and without

compensation 202

5.23 Active power at mid point with and without

compensation 202

5.24 Reactive power at mid point with and without

compensation 203

5.25 Optimal location of STATCOM for active

power compensation 204

5.26 Optimal location of STATCOM for reactive

power compensation 205

xxvi

LIST OF ABBREVIATIONS

ACF - AC Filter

ASD - Adjustable Speed Drive

ASVC - Advanced Static Var Compensator

AC - Alternating Current

APOD - Alternative Phase Opposition Disposition

AEP - American Electric Power

ACMC - Asymmetric Cascaded Multilevel Converter

APFR - Automatic Power Factor Regulator

CCMC - Capacitor Clamped Multilevel Converter

CCMLI - Capacitor Clamped Multi Level Inverter

CMC - Cascaded Multilevel Converter

CMI - Cascaded Multilevel Inverter

CSC - Current Source Converter

DAE - Differential Algebraic Equations

DSP - Digital Signal Processor

DCMC - Diode Clamped Multilevel Converter

DCMLI - Diode Clamped Multi Level Inverter

DC - Direct Current

DVR - Dynamic Voltage Restorer

ESR - Effective Series Resistance

EPRI - Electric Power Research Institute

EMTDC - Electro Magnetic Transient DC

ESS - Energy Storage System

FERC - Federal Energy Regulatory Commission

FPGA - Field Programmable Gate Array

xxvii

FC TCR - Fixed Capacitor Thyristor Controlled Reactor

FSIG - Fixed Speed Induction Generator

FSWT - Fixed Speed Wind Turbine

FSWECS - Fixes Speed Wind Energy Conversion System

FACTS - Flexible AC Transmission Systems

FCMC - Flying Capacitor Multilevel Converter

FCMLI - Flying Capacitor Multi Level Inverter

FBC - Full Bridge Converter

FBI - Full Bridge Inverter

FFS - Fundamental Frequency Switching

GTO - Gate Turn Off

HSF - High Switching Frequency

HBBB - Hybrid Bridge Building Block

IPFC - Interline Power Flow Controller

ISPWM - Inverted Sine Pulse Width Modulation

LVRT - Low Voltage Ride Through

MCPWM - Multi Carrier Pulse Width Modulation

MLI - Multi Level Inverter

NPC - Neutral Point Clamped

NPCMC - Neutral Point Clamped Multilevel Converter

NR - Newton Raphson

OLTC - On Load Tap Changing

PD - Phase Disposition

PLL - Phase Locked Loop

PLO - Phase Locked Oscillator

POD - Phase Opposition Disposition

PS - Phase Shifted

PST - Phase Shifting Transformer

PCC - Point of Common Coupling

xxviii

PCS - Power Conditioning System

PSCAD - Power System Computer Aided Design

PI - Proportional Integral

PDM - Pulse Duration Modulation

PWM - Pulse Width Modulation

RMS - Root Mean Square

SHE - Selective Harmonic Elimination

SDCS - Seperated DC Sources

SPWM - Sinusoidal Pulse Width Modulation

SVM - Space Vector Modulation

SVPWM - Space Vector Pulse Width Modulation

SCIG - Squirrel Cage Induction Generator

STATCON - STATic CONdenser

STATCOM - STATic synchronous COMpensator

SSSC - Static Synchronous Series Compensator

SVC - Static Var Compensator

SVG Static Var Generator

SMES - Super Conducting Magnetic Energy Storage

SCADA - Supervisory Control and Data Acquisition

SCMLI - Symmetrical Cascaded Multi Level Inverter

SLBCS - Synchronous Link Based Control Scheme

TVA - Tennessee Valley Authority

TCPAR - Thyristor Controlled Phase Angle Regulator

TCPST - Thyristor Controlled Phase Shifting Transformer

TCR - Thyristor Controlled Reactor

TCSC - Thyristor Controlled Switched Capacitor

TSC - Thyristor Switched Capacitor

THD - Total Harmonic Distortion

TSO - Transmission System Operation

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UCAP - Ultra CAPacitor

UPFC - Unified Power Flow Controller

VFISPWM - Variable Frequency Inverted Sine Pulse Width

Modulation

VAR - Volt Ampere Reactive

VSC - Voltage Source Converter

VSI - Voltage Source Inverter

WECS - Wind Energy Conversion System

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