wide area monitoring, protection and control in future great britain power system

8/10/2019 Wide Area Monitoring, Protection and Control in Future Great Britain Power System

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WIDE AREA MONITORING, PROTECTION

AND CONTROL IN THE FUTURE GREAT

BRITAIN POWER SYSTEM

A thesis submitted to the

University of Manchester

For the degree ofDoctor of Philosophy

In the Faculty of Engineering and Physical Sciences

2012

By

Deyu Cai

School of Electrical and Electronic Engineering


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Preface

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List of ContentsList of Contents ............................................................................................................... 1

List of Figures .................................................................................................................. 4

List of Tables ................................................................................................................. 10

Abstract .......................................................................................................................... 13

List of Abbreviations .................................................................................................... 14

Declaration ..................................................................................................................... 15

Copyright Statement ..................................................................................................... 16

Acknowledgements ........................................................................................................ 18

Chapter 1 Introduction ................................................................................................. 19

1.1 Research Background ........................................................................................... 19

1.1.1 Power system blackouts ................................................................................. 19 1.1.2 Wide area monitoring, protection and control ............................................... 22

1.2 Objectives of the Research .................................................................................... 24

1.3 Thesis Structure ..................................................................................................... 26 1.4 Main Contributions of This Research ................................................................... 28

Chapter 2 Synchronized Measurement Technology .................................................. 29

2.1 Introduction ........................................................................................................... 29

2.2 Phasor Measurement Unit ..................................................................................... 31

2.3 Data Concentrator ................................................................................................. 34

2.4 Synchrophasor Standard ....................................................................................... 35

2.5 Summary ............................................................................................................... 35

Chapter 3 Applications and Benefits of Synchronized Measurement Technology . 36

3.1 Introduction ........................................................................................................... 36

3.2 Off-line Applications of SMT ............................................................................... 36

3.2.1 Post-disturbance analysis ............................................................................... 36 3.2.2 Benchmarking, validation and fine-tuning of system models ........................ 38

3.3 On-line Applications of SMT ............................................................................... 39

3.3.1 Wide area phase angular and power flow monitoring ................................... 39 3.3.2 Wide area frequency monitoring .................................................................... 41 2.3.3 Wide area voltage monitoring ........................................................................ 42 3.3.4 Inter-area oscillation monitoring .................................................................... 44 3.3.5 Power system restoration ............................................................................... 45 3.3.6 Improved state estimation .............................................................................. 47

3.3.7 Dynamic rating of overhead transmission lines ............................................. 48 2.3.8Intelligent controlled islanding ....................................................................... 49 2.3.9 Adaptive under-frequency load shedding ...................................................... 50

3.4 Conclusions ........................................................................................................... 51

Chapter 4 Architecture of a WAMPAC System ........................................................ 52

4.1 Introduction ........................................................................................................... 52

4.2 Architecture of a WAMPAC System .................................................................... 52

4.3 Communication Networks of WAMPAC System ................................................ 55

4.3.1 Available communication media for WAMPAC ........................................... 55 4.3.2 Communication protocols and format for phasor data transmission ............. 57

4.3.3 Communication latency ................................................................................. 59 4.4 Architecture of future GB WAMPAC system ...................................................... 59

4.5 Conclusions ........................................................................................................... 61


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Chapter 5 The Roadmap to the Future GB WAMPAC System ............................... 62

5.1 Introduction ........................................................................................................... 62

5.2 The Roadmap to a WAMPAC System ................................................................. 63

5.3 The Future GB Power System .............................................................................. 65

5.4 GBs strategy for WAMPAC ................................................................................ 68

5.4.1 Short term strategy ......................................................................................... 68 5.4.2 Long term strategy ......................................................................................... 71

5.5 Conclusions ........................................................................................................... 81

Chapter 6 The Physical Nature of Inter-area Oscillations in Electrical PowerSystems ........................................................................................................................... 82

6.1 Introduction ........................................................................................................... 82

6.2 Nonlinear Simulations ........................................................................................... 82

6.2.1 Local oscillatory mode in Area 1 ................................................................... 83 6.2.2 Local oscillatory mode in Area 2 ................................................................... 84 6.2.3 Inter-area oscillatory mode ............................................................................ 85 6.2.4 Large disturbance ........................................................................................... 87

6.3 Modal Analysis ..................................................................................................... 88 6.3.1 Dynamic system representation ..................................................................... 89 6.3.2 System linearization for modal analysis ........................................................ 90 6.3.3 Eigenvalues and eigenvectors ........................................................................ 92 6.3.4 Eigenvalues and small signal stability ........................................................... 93 6.3.5 Participation factors ....................................................................................... 94 6.3.6 Modal analysis for inter-area oscillation study .............................................. 95

6.4 The origin of lightly damped/unstable inter-area oscillations ............................ 100

6.5 Conclusions ......................................................................................................... 102

Chapter 7 Inter-area Oscillation Monitoring Using Newton-Type Algorithm ..... 104

7. 1 Introduction ........................................................................................................ 104 7.2 Signal Model Representation .............................................................................. 105

7.3 Newton Type Algorithm Derivation ................................................................... 108

7.4 Computer Simulated Tests .................................................................................. 110

7.4.1 Static tests .................................................................................................... 111 7.4.2 Noise tests .................................................................................................... 113 7.4.3 Dynamic tests ............................................................................................... 116

7.5 Dynamic Simulation of a Multi-machine System ............................................... 118

7.6 Real-life Conditions Tests ................................................................................... 122

7.7 Conclusions ......................................................................................................... 124

Chapter 8 The Application of Power Electronic Devices for Damping Inter-areaoscillations .................................................................................................................... 126

8.1 Introduction ......................................................................................................... 126

8.2 Modal Analysis for Control ................................................................................ 127

8.2.1 Transfer functions ........................................................................................ 127 8.2.2 Residue based damping controller design .................................................... 128

8.3 Inter-area Oscillation Damping Control with HVDC ......................................... 131

8.3.1 HVDC transmission system modelling ........................................................ 132 8.3.2 System performance without HVDC damping controller ............................ 139 8.3.3 Residue based HVDC damping controller design ....................................... 140 8.3.4 System performance with a HVDC damping controller .............................. 143

8.4 Inter-area Oscillation Control with TCSC .......................................................... 146

8.4.1 TCSC modelling .......................................................................................... 146


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8.4.2 System performance without TCSC damping controller ............................. 148 8.4.3 Residue based TCSC damping controller design ......................................... 149 8.4.4 System performance with TCSC damping controller .................................. 151

8.5 Inter-area Oscillation Control with SVC............................................................. 154

8.5.1 SVC modelling ............................................................................................. 154 8.5.2 System performance without SVC damping controller ............................... 155

8.5.3 Residue based SVC damping controller design ........................................... 157 8.5.4 System performance with SVC damping controller .................................... 158 8.6 Conclusions ......................................................................................................... 162

Chapter 9 Wide Area Monitoring and Control System (WAMCS) in a Future GBPower System ............................................................................................................... 163

9.1 Introduction ......................................................................................................... 163

9.2 Assessment of the Inter-area Oscillations in GB Power System ........................ 163

9.2.1 GB power system modelling ........................................................................ 163 9.2.2 Inter-area oscillations study in GB power system........................................ 165

9.3 Wide Area Monitoring and Control System (WAMCS) in a Future GB Power

System ....................................................................................................................... 170 9.3.1 Architecture of WAMCS in GB power system ........................................... 170 9.3.2 Inter-area oscillation monitoring using NTA ............................................... 172 9.3.3 Wide area inter-area oscillation damping control with HVDC in GB ......... 174 9.3.4 The impact of time delays on wide-area control .......................................... 177 9.3.5 Interaction between PSSs and HVDC damping control system .................. 180

9.4 Conclusions ......................................................................................................... 182

Chapter 10 Conclusions and Future Work ............................................................... 184

10.1 Conclusions ....................................................................................................... 184

10.2 Future Work ...................................................................................................... 187

References .................................................................................................................... 190 Appendices ................................................................................................................... 196

10.1 Appendix A ....................................................................................................... 196

10.2 Appendix B ....................................................................................................... 199

10.3 Appendix C ....................................................................................................... 205

10.4 Appendix D ....................................................................................................... 210

10.5 Appendix E ....................................................................................................... 213

10.6 Appendix F ........................................................................................................ 217

10.7 Appendix G ....................................................................................................... 221

10.7.1 Published journal papers ............................................................................ 221 10.7.2 Submitted journal papers ........................................................................... 221 10.7.3 Published conference papers ...................................................................... 221


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List of FiguresFigure 1.1: Statistics of blackouts: customers affected ................................................... 19

Figure 1.2: Line of separation from the European grid ................................................... 20

Figure 1.3: A Generalized WAMPAC system ................................................................ 23

Figure 2.1: Phasor representation of a sinusoidal signal ................................................. 30

Figure 2.2: Synchronized phasor measurement in remote substations ........................... 30

Figure 2.3: A functional block diagram of a typical PMU ............................................. 31

Figure 2.4: State estimation v.s. PMU measurements .................................................... 32

Figure 2.5: Two standalone PMUs ................................................................................. 32

Figure 2.6: Two integrated PMUs................................................................................... 33

Figure 2.7: Data concentrator in a WAMPAC system .................................................... 34

Figure 2.8: SEL Data Concentrator ................................................................................. 34

Figure 3.1: The reconstruction of system frequencies after a large disturbance in WECC,14th June, 2004 ............................................................................................................... 37

Figure 3.2: Comparison of the recorded system response to the 10th August, 1996disturbance in USA with the simulation results .............................................................. 38

Figure 3.3: RTDMS a wide area visualization platform for the North American powersystem.............................................................................................................................. 40

Figure 3.4: Disturbance localization using PMUs and the triangulation method ........... 42

Figure 3.5: Estimation of the Thevenin equivalent with local measurements ................ 43

Figure 3.6: T and Thevenin representation of transmission corridor .............................. 44

Figure 3.7: Oscillations observed by two PMUs in the European grid ........................... 45

Figure 3.8: PMU measurements from three areas during reclosing attempts: UCTE, 4

November 2006 ............................................................................................................... 46

Figure 3.9: PMUs installed at both ends of a transmission line ...................................... 48

Figure 3.10: Visualization of the real time mentoring of the thermal condition of anoverhead transmission corridor in APG .......................................................................... 49

Figure 4.1: The general architecture of a typical WAMPAC system ............................. 53

Figure 4.2: The combination of different communication media for a WAMPAC system......................................................................................................................................... 57

Figure 4.3: Generic schematic of the dataflow in WAMPAC system ............................ 58

Figure 4.4: A simple demonstration of communication latency in WAMPAC system .. 59

Figure 4.5: A general architecture of future GB WAMPAC system .............................. 60

Figure 5.1: WAMPAC application tree with full smart fruits ..................................... 63 Figure 5.2: Roadmap for deploying PMU applications .................................................. 64

Figure 5.3: UK energy target 2020 and 2030 .................................................................. 66

Figure 5.4: Power transfers across the boundary between Scotland and England at peakload condition .................................................................................................................. 66

Figure 5.5: New TCSC and HVDC in GB transmission networks ................................. 67

Figure 5.6: Locations of off-shore wind farms in GB power system (2020-2030) ........ 67

Figure 5.7: Logical filter one The number of PMUs required .................................. 69

Figure 5.8: Logical filter two Commercial availability of PMU applications .......... 69

Figure 5.9: Logical filter three Necessity of PMU application for investors ............ 69 Figure 5.10: Global power angle and frequency monitoring system .............................. 70

Figure 5.11: Real time monitoring system over inter-tie corridors ................................. 71


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Figure 5.12: PMU placements in SHPTN ....................................................................... 72

Figure 5.13: PMU placements at the boundary between Scotland and England ............ 73

Figure 5.14: PMU placements in central England .......................................................... 74

Figure 5.15: PMU placements in the South of England ................................................. 74

Figure 5.16: A PMU installed in the Torness substation ................................................ 75

Figure 5.17: Three PMUs installed in the Crekey Beck, Keadby and Grimsby Westsubstations ....................................................................................................................... 75

Figure 5.18: One PMU installed in the Sizewell substation ........................................... 76

Figure 5.19: Two PMUs installed in the North Wales substations of Wylfa and Stanah76

Figure 5.20: A PMU installed in the Alverdiscott substation ......................................... 76

Figure 5.21: PMU placements for the future GB wide area monitoring system ............. 77

Figure 5.22: A SMT-based adaptive UFLS scheme in the future GB power system ..... 78

Figure 5.23: Inter-area oscillation damping control with power electronic devices in GB power system ................................................................................................................... 79

Figure 5.24: Closed loop inter-area oscillation control using HVDC ............................. 80

Figure 5.25: Closed loop inter-area oscillation control using TCSC .............................. 81 Figure 6.1: A typical two-area system ............................................................................ 83

Figure 6.2: Generator rotor speed responses to the disturbances occurred in area 1 ...... 84

Figure 6.3: Generator rotor speed responses to the disturbances occurred in area 2 ...... 85

Figure 6.4: Generator rotor speed oscillations dominated by inter-area mode ............... 85

Figure 6.5: System frequency responses in inter-area mode........................................... 86

Figure 6.6: Oscillatory active power flow on transmission line 3 .................................. 87

Figure 6.7: Oscillatory active power flow on transmission line 1 .................................. 87

Figure 6.8: Responses of the Generator rotor speeds to the large disturbance ............... 88

Figure 6.9: Active power transfer over the tie line after the disturbance ........................ 88

Figure 6.10: Oscillatory modes in the two-area system .................................................. 97

Figure 6.11: Right eigenvector (mode shape) of inter-area mode .................................. 99

Figure 6.12: The effect of inter-area power flow on system oscillatory mode ............. 101

Figure 7.1: A global block diagram of the test procedure............................................. 111

Figure 7.2: Computer generated test signal .................................................................. 112

Figure 7.3: Estimation results of the magnitude of DC component, A 0 ....................... 112

Figure 7.4: Estimation results of the magnitude of oscillatory component A 1 ............. 112

Figure 7.5: Estimation results of the damping factor of oscillatory component, ..... 112

Figure 7.6: Estimation results of the frequency of oscillatory component, f . ............... 113

Figure 7.7: Estimation results of the phase angle of oscillatory component, ........... 113

Figure 7.8: Computer generated test signal and estimated signal ................................. 113

Figure 7.9: Algorithm tracking capabilities in presence of noise ................................. 115

Figure 7.10: Computer generated signal with step change of .................................. 116

Figure 7.11: Estimation results of the magnitude of DC component, A0, for differentTdw ................................................................................................................................. 116

Figure 7.12: Estimation results of the magnitude of oscillatory component, A1, fordifferent T dw .................................................................................................................. 117

Figure 7.13: Estimation results of damping factor, , for different T dw ....................... 117

Figure 7.14: Estimation results of the frequency of oscillatory component, f , fordifferent T dw .................................................................................................................. 117


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Figure 7.15: Estimation results of the phase angle of oscillatory component, , for

different T dw .................................................................................................................. 117

Figure 7.16: Dynamic testing: comparison between the actual and estimated signal ... 118

Figure 7.17: A block diagram of the testing procedure based on dynamic simulation of amulti-machine test system ............................................................................................. 118

Figure 7.18: Two-area test system with HVDC link .................................................... 119

Figure 7.19: Generator rotor speed changes after the disturbance ................................ 119

Figure 7.20: Inter-area oscillatory mode shape estimated by NTA .............................. 120

Figure 7.21: Oscillatory active power (on line 2) after the disturbance ....................... 121

Figure 7.22: Estimated frequency of the inter-area oscillatory mode by NTA and Pronymethod ........................................................................................................................... 121

Figure 7.23: Estimated damping factor of the inter-area oscillatory mode by NTA andProny method ................................................................................................................ 121

Figure 7.24: Estimated frequency of the inter-area oscillatory mode by reduced-orderProny method and NTA ................................................................................................ 122

Figure 7.25: Estimated damping factor of the inter-area oscillatory mode by reduced-order Prony method and NTA ....................................................................................... 122

Figure 7.26: Estimated oscillatory active power from estimated parameters ............... 122

Figure 7.27: Oscillatory voltage phase angle difference between Glasgow and London....................................................................................................................................... 123

Figure 7.28: Estimated frequency of inter-area oscillatory mode in the GB network .. 123

Figure 7.29: Estimated damping ratio of inter-area oscillatory mode in the GB network ....................................................................................................................................... 124

Figure 7.30: Oscillatory signal based on estimated oscillatory parameters .................. 124

Figure 8.1: Closed loop system with feedback control ................................................. 129 Figure 8.2: The structure of a feedback damping control ............................................. 129

Figure 8.3: The shift of an eigenvalue caused a feedback damping control ................. 130

Figure 8.4: A two-area system with HVDC .................................................................. 131

Figure 8.5: Two types of power converters .................................................................. 132

Figure 8.6: Rectifier equivalent circuit ......................................................................... 133

Figure 8.7: Inverter equivalent circuit ........................................................................... 134

Figure 8.8: Monopolar HVDC link ............................................................................... 135

Figure 8.9: Bipolar HVDC link..................................................................................... 135

Figure 8.10: Homopolar HVDC link ............................................................................ 136

Figure 8.11: Equivalent circuit of HVDC link .............................................................. 136

Figure 8.12: Voltage profile of the equivalent circuit of HVDC link ........................... 136

Figure 8.13: Basic control scheme of HVDC system ................................................... 138

Figure 8.14: Inverters control for constant voltage .................................................. 138

Figure 8.15: Rectifiers control for constant current ................................................. 138

Figure 8.16: Oscillatory modes in the two-area system with HVDC ........................... 139

Figure 8.17: Generator rotor speed responses to the small disturbances without HVDCdamping control ............................................................................................................ 140

Figure 8.18: System frequency responses to the small disturbances without HVDC

damping control ............................................................................................................ 140 Figure 8.19: Rectifier control with supplementary damping control ............................ 141

Figure 8.20: Feedback control with multiple input signals ........................................... 141


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Figure 8.21: An illustration of the estimation of the phase angle of the residue .......... 142

Figure 8.22: An estimation of the residues phase angle for HVDC damping controldesign ............................................................................................................................ 143

Figure 8.23: Oscillatory modes versus the gain of HVDC damping controller ............ 144

Figure 8.24: Generator rotor speed responses to the small disturbances with and withoutHVDC damping control ................................................................................................ 144

Figure 8.25: Active power flow (line 3) responses to the small disturbances with andwithout HVDC damping control ................................................................................... 145

Figure 8.26: Generator rotor speed responses to a three-phase fault with and withoutHVDC damping control ................................................................................................ 145

Figure 8.27: Active power flow (line 3) responses to a three-phase fault with andwithout HVDC damping control ................................................................................... 146

Figure 8.28: Typical two-area system with TCSC ........................................................ 146

Figure 8.29: A structure of a typical TCSC .................................................................. 147

Figure 8.30: An ideal model of TCSC for power system stability study ...................... 147

Figure 8.31: An equivalent circuit of the transmission corridor with TCSC ................ 147 Figure 8.32: A block diagram of TCSC control ............................................................ 148

Figure 8.33: Oscillatory modes in the two-area system with TCSC ............................. 148

Figure 8.34: Generator rotor speed responses to the small disturbances without TCSCdamping control ............................................................................................................ 149

Figure 8.35: System frequency responses to the small disturbances without TCSCdamping control ............................................................................................................ 149

Figure 8.36: A block diagram TCSC supplementary damping control ........................ 150

Figure 8.37: An estimation of the residues phase angle for TCSC damping control

design ............................................................................................................................ 150

Figure 8.38: Oscillatory modes versus the gain of TCSC damping controller ............. 151

Figure 8.39: Generator rotor speed responses to the small disturbances with and withoutTCSC damping control ................................................................................................. 152

Figure 8.40: Active power flow (line 3) responses to small disturbance with and withoutTCSC damping control ................................................................................................. 152

Figure 8.41: Generator rotor speed responses to a three-phase fault with and withoutTCSC damping control ................................................................................................. 153

Figure 8.42: Active power flow (line 3) responses to a three-phase fault with andwithout TCSC control ................................................................................................... 153

Figure 8.43: Modified two-area system with SVC ....................................................... 154 Figure 8.44: A structure of a typical SVC .................................................................... 154

Figure 8.45: An ideal model of SVC ............................................................................ 155

Figure 8.46: Block diagram of SVC control ................................................................. 155

Figure 8.47: Oscillatory modes in the two-area system with SVC ............................... 156

Figure 8.48: Generator rotor speed responses to the small disturbances without SVCdamping control ............................................................................................................ 156

Figure 8.49: Oscillatory voltage angle difference between bus3 and bus5 caused by thedisturbances ................................................................................................................... 157

Figure 8.50: A block diagram of a SVC damping controller ........................................ 157 Figure 8.51: An estimation of the residues phase angle for SVC damping control design....................................................................................................................................... 158


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Figure 8.52: Oscillatory modes versus the gain of SVC damping controller ............... 159

Figure 8.53: Generator rotor speed responses to the small disturbances with and withoutSVC damping control .................................................................................................... 160

Figure 8.54: Active power flow (line 3) responses to small disturbance with and withoutSVC damping control .................................................................................................... 160

Figure 8.55: Generator rotor speed responses to a three-phase fault with and withoutSVC damping control .................................................................................................... 161

Figure 8.56: Active power flow (line 3) responses to a three-phase fault with andwithout SVC damping control ...................................................................................... 161

Figure 9.1: 500 kV HVDC links and 400 kV Series Compensators that are installed inthe GB power system (vision 2015) .............................................................................. 164

Figure 9.2: Inter-area oscillation monitoring SPTN and NGETN ................................ 165

Figure 9.3: Three large generators selected in Scotland for monitoring inter-areaoscillations .................................................................................................................... 166

Figure 9.4: Three large generators selected in central England for monitoring inter-area

oscillations .................................................................................................................... 166 Figure 9.5: Two large generators selected in the South of England for monitoring inter-area oscillations ............................................................................................................. 167

Figure 9.6: The oscillatory inter-area power flow on the Harker-Hutton line after a largedisturbance .................................................................................................................... 167

Figure 9.7: The system frequency variations caused by a large disturbance ................ 168

Figure 9.8: The oscillatory inter-area power flow caused by a large disturbance in theoriginal and PSSs-reduced GB system.......................................................................... 168

Figure 9.9: System frequency variations caused by the large disturbance in the PSSs-

reduced system .............................................................................................................. 169

Figure 9.10: System frequency variations measured in substations HUER and DEES inthe PSSs-reduced system .............................................................................................. 169

Figure 9.11: Architecture of the wide-area inter-area oscillation monitoring and controlsystem in GB ................................................................................................................. 172

Figure 9.12: Inter-area oscillation mode identified by NTA in GB system .................. 173

Figure 9.13: Estimated inter-area oscillation mode shape of GB system ..................... 173

Figure 9.14: Schematic diagram of HVDC damping system ........................................ 174

Figure 9.15: Responses of the generator rotor speeds (PEHE, LOAN, HUER and EGGB)to the large disturbance with and without the wide area HVDC damping control ....... 175

Figure 9.16: Responses of the generator rotor speeds (WBUR, RUGE, SIZE and DUNG)to the large disturbance with and without the wide area HVDC damping control ....... 176

Figure 9.17: The response of the inter-area power flow on the Harker-Hutton line to thelarge disturbance, with and without HVDC damping control ...................................... 176

Figure 9.18: Inter-area oscillation mode identified by NTA in the GB system, with andwithout HVDC damping control ................................................................................... 177

Figure 9.19: An illustration of the time delay involved in the data transmission in GBWAMCS........................................................................................................................ 178

Figure 9.20: A block diagram of HVDC damping controllers (with time delay) ......... 178

Figure 9.21: The effect of time delay in the wide area damping controllers(50 milliseconds to 200 milliseconds) .......................................................................... 179


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Figure 9.22: The effect of time delay in the wide area damping controllers(300 milliseconds to 700 milliseconds)......................................................................... 179

Figure 9.23: Responses of the generator rotor speeds (PEHE, LOAN, HUER and EGGB)to the large disturbance (all PSSs in service) ................................................................ 180

Figure 9.24: Responses of the generator rotor speeds (WBUR, RUGE, SIZE and DUNG)to the large disturbance (all PSSs in service) ................................................................ 181

Figure 9.25: The influence of HVDC damping control on the inter-area power flow incomplete GB system ..................................................................................................... 182

Figure A-1: A single line diagram of two-area system ................................................. 196

Figure A-2: Block diagram of static exciter of G1, G2 and G3 and G4 ....................... 197

Figure A-3: Block diagram of speed governor of G1, G2, G3 and G4 ......................... 197

Figure B-1: A single line diagram of the two-area system with HVDC ....................... 199

Figure B-2: Block diagram of DC exciter of G1, G3 and G4 ....................................... 200

Figure B-3: Block diagram of static exciter of G2 ........................................................ 200

Figure B-4: Block diagram of speed governor of G1, G2, G3 and G4 ......................... 201

Figure B-5: Rectifier operation condition (DIgSILENT interface) .............................. 202 Figure B-6: Rectifiers control for constant current................................................... 202

Figure B-7: Inverter operation condition (DIgSILENT interface) ................................ 203

Figure B-8: inverters control for constant voltage .................................................... 203

Figure C-1: A single line diagram of the two-area system with HVDC ....................... 205

Figure C-2: Block diagram of static exciter of G1, G2 G3 and G4 .............................. 205

Figure C-3: Block diagram of speed governor of G1, G2, G3 and G4 ......................... 206

Figure C-4: Rectifier operation condition (DIgSILENT interface) .............................. 207

Figure C-5: Rectifiers control for constant current................................................... 207

Figure C-6: Inverter operation condition (DIgSILENT interface) ................................ 208

Figure C-7: inverters control for constant voltage .................................................... 208

Figure C-8: Rectifier control with supplementary damping control ............................. 209

Figure D-1: A single line diagram of the two-area system with TCSC ........................ 210

Figure D-2: Block diagram of static exciter of G1, G2 and G3 and G4 ....................... 210

Figure D-3: Block diagram of speed governor for G1, G2, G3 and G4 ....................... 211

Figure D-4: TCSC with supplementary damping control. ............................................ 211

Figure E-1: A single line diagram of the two-area system with SVC ........................... 213

Figure E-2: Block diagram of static exciter of G1, G2 and G3 and G4 ........................ 213

Figure E-3: Block diagram of speed governor of G1, G2, G3 and G4 ......................... 214

Figure E-4: SVC composite (DIgSILENT interface) .................................................... 215 Figure E-5: Primary voltage control of SVC ................................................................ 215

Figure E-6: SVC supplementary damping controller .................................................... 216

Figure F-1: Rectifier operation condition (DIgSILENT interface) ............................... 217

Figure F-2: Rectifiers control for constant current ................................................... 217

Figure F-3: Inverter operation condition (DIgSILENT interface) ................................ 218

Figure F-4: inverters control for constant voltage .................................................... 218

Figure F-5: HVDC supplementary damping controller in GB full model .................... 219


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List of TablesTable 2.1: Summary of available standalone and integraed PMUs ................................ 33

Table 5.1: Three scenarios for meeting the 2020 UK renewable targets ........................ 66

Table 6.1: Eigenvalues of the two-area system ............................................................... 96

Table 6.2: Oscillation modes in the two-area system ..................................................... 97

Table 6.3: Right eigenvector for eigenvalue 28 (associated with inter-area mode) ....... 98

Table 6.4: Participation vector for Eigenvalue 28 (associated with inter-area mode) .. 100

Table 6.5: The effect of inter-area power flow on inter-area mode .............................. 101

Table 6.6: Effect of inter-tie line impedance on inter-area mode ................................. 102

Table 7.1: Sensitivity analysis for random noise .......................................................... 114

Table 7.2: Sensitivity analysis for sampling for frequency .......................................... 115

Table 7.3: Sensitivity analysis for data window size .................................................... 115

Table A-1: Synchronous machine parameters of G1, G2 and G3 and G4 .................... 196

Table A-2: Power generation conditions of G1, G2 and G3 and G4 ............................ 196

Table A-3: Parameters of static exciter ......................................................................... 197 Table A-4: Parameters of speed governor ..................................................................... 197

Table A-5: Transformer parameters .............................................................................. 197

Table A-6: AC transmission line parameters ................................................................ 198

Table A-7: Load data .................................................................................................... 198

Table A-8: Shunt capacitors .......................................................................................... 198

Table B-1: Synchronous machine parameters of G1, G2 and G3 and G4 .................... 199

Table B-2: Power generation conditions of G1, G2 and G3 and G4 ............................ 199

Table B-3: Parameters of DC exciter ............................................................................ 200

Table B-4: Parameters of static exciter ......................................................................... 201

Table B-5: Parameters of speed governor ..................................................................... 201

Table B-6: Transformer parameters .............................................................................. 201

Table B-7: AC transmission line parameters ................................................................ 201

Table B-8: DC transmission line parameters ................................................................ 202

Table B-9: Parameters of rectifier control .................................................................... 202

Table B-10: Parameters of inverter control ................................................................... 203

Table B-11: Load data ................................................................................................... 203

Table B-12: Shunt capacitors ........................................................................................ 204

Table C-1: Synchronous machine parameters of G1, G2 and G3 and G4 .................... 205

Table C-2: Power generation conditions of G1, G2 and G3 and G4 ............................ 205 Table C-3: Parameters of static exciter ......................................................................... 206

Table C-4: Parameters of speed governor ..................................................................... 206

Table C-5: Transformer parameters .............................................................................. 206

Table C-6: AC transmission line parameters ................................................................ 206

Table C-7: DC transmission line parameters ................................................................ 207

Table C-8: Parameters of rectifier control .................................................................... 207

Table C-9: Parameters of inverter control ..................................................................... 208

Table C-10: Parameters of HVDC supplementary control ........................................... 209

Table C-11: Load data ................................................................................................... 209 Table C-12: Shunt capacitors ........................................................................................ 209

Table D-1: Synchronous machine parameters of G1, G2 and G3 and G4 .................... 210


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Table D-2: Power generation conditions of G1, G2 and G3 and G4 ............................ 210

Table D-3: Parameters of Static Exciter ........................................................................ 211

Table D-4: Parameters of Governor .............................................................................. 211

Table D-5: The capacitor and reactor of TCSC under steady state ............................... 211

Table D-6: Parameters of TCSC supplementary damping control ............................... 212

Table D-7: Transformer parameters .............................................................................. 212

Table D-8: Transmission line parameters ..................................................................... 212

Table D-9: Load data .................................................................................................... 212

Table D-10: Shunt capacitors ........................................................................................ 212

Table E-1: Synchronous machine parameters of G1, G2 and G3 and G4 .................... 213

Table E-2: Power generation conditions of G1, G2 and G3 and G4............................. 213

Table E-3: Parameters of static exciter ......................................................................... 214

Table E-4: Parameters of speed governor ..................................................................... 214

Table E-5: Transformer parameters .............................................................................. 214

Table E-6: Transmission line parameters ...................................................................... 214

Table E-7: Load data ..................................................................................................... 215 Table E-8: Shunt capacitors .......................................................................................... 215

Table E-9: Parameters of the primary voltage control of SVC ..................................... 215

Table E-10: Parameters of the primary voltage control of SVC ................................... 216

Table F-1: DC transmission line parameters ................................................................. 217

Table F-2: Parameters of rectifier control ..................................................................... 217

Table F-3: Parameters of rectifier control ..................................................................... 218

Table F-4: Parameters of the HVDC damping controller ............................................. 219

Table F-5: A list of the PSS in service .......................................................................... 220


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AbstractThe growing issue of power-grid congestion and a global increase in disturbances haveemphasized the need to enhance electrical power networks using Wide Area Monitoring,Protection, and Control (WAMPAC). This is a cost-effective solution for improving

power system planning and operation. In addition to these existing issues, the Great

Britain (GB) power system is facing significant changes, in terms of both powertransmission technology and the nature of the generation mix, that will cause theoperation of the future GB power system to become more unpredictable and complex.Therefore, developing a WAMPAC system will be essential to enhance the stability andoptimise the operation of the future GB power system.

The main objectives of the research presented in this thesis are to design a GBWAMPAC system and develop solutions to overcome the challenges that will beinvolved in the initial stage of the GB WAMPAC project.

As Synchronized Measurement Technology (SMT) is the most essential element andenabler of WAMPAC, this thesis first provides a study of SMT and its applications.This study also reviews the state of the art of these SMT applications, and worldwideexperience with the operation of WAMPAC in terms of system architecture,communication technologies and data management.

After the basic study of WAMPAC, this thesis presents a new methodology fordesigning a roadmap that will ensure the future GB WAMPAC system will bedeveloped in a logical and economic manner. This methodology takes into account theinternational experience with WAMPAC project management and the practicalchallenges faced in the future GB power system. With this new methodology, the GBstrategies for the development of WAMPAC are devised.

Two major SMT applications are then developed that can form main parts of the proposed future GB WAMPAC system. These applications are developed to enhancethe small signal stability of the future GB power system.

1. Wide Area Inter-area Oscillation Monitoring using Newton Type Algorithm.2. Wide Area Inter-area Oscillation Control using Power Electronic Devices.

Finally, the operation of a proposed GB WAMPAC system is demonstrated using theDIgSILENT software package. The proposed real time applications are tested and

evaluated using dynamic simulations of a full GB power system model. In addition,some key factors that will influence the operation of the future GB WAMPAC systemwill be analyzed and discussed.


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List of AbbreviationsWAMS Wide Area Monitoring SystemWAMCS Wide Area Monitoring, Control SystemWAMPAC Wide Area Monitoring, Protection and ControlGPS Global Positioning SystemIED Intelligent |Electronic DeviceSMT Synchronized Measurement TechnologyPMU Phasor Measurement UnitDC Data ConcentratorISO Independent System OperatorEMS Energy Management SystemSCADA Supervisory Control and Data AcquisitionSIPS System Integrity Protection SchemeSPS System Protection Scheme

WECC Western Electricity Coordinating CouncilEIPP Eastern Interconnection Phasor ProjectADSL Advanced Digital Signal LinkVPN Virtual Private NetworksTCP Transport Control ProtocolUDP User Datagram ProtocolIP Internet protocolSE State EstimationPE Parameter Estimation

RTDMS Real Time Dynamic Monitoring SystemFNET Frequency Monitoring NetworkVIP Voltage Instability PredictorUVLS Under-Voltage Load SheddingUFLS Under-Frequency Load SheddingKF Kalman FilterFFT Fast Fourier TransformLS Least Square

NTA Newton Type AlgorithmHVDC High Voltage Direct CurrentCSC Current Source ConverterVSC Voltage Source ConverterTCSC Thyristor Controlled Series CompensatorSVC Static Var CompensatorAVR Automatic Voltage RegulatorTG Turbine GovernorPSS Power System StabilizerSPTN Scottish Power Transmission NetworkSHETN Scottish Hydro-Electric Transmission Network

NGETN National Grid Electricity Transmission Network


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Declaration No portion of the work referred to in the thesis has been submitted in support of an

application for another degree or qualification of this or any other university or other

institute of learning.


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Preface

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Copyright Statementi. The author of this thesis (including any appendices and/or schedules to this

thesis) owns certain copyright or related rights in it (the Copyright) and he has

given The University of Manchester certain rights to use such Copyright,

including for administrative purposes.

ii. Copies of this thesis, either in full or in extracts and whether in hard or

electronic copy, may be made only in accordance with the Copyright, Designs

and Patents Act 1988 (as amended) and regulations issued under it or, where

appropriate, in accordance with licensing agreements which the University has

from time to time. This page must form part of any such copies made.

iii. The ownership of certain Copyright, patents, designs, trade marks and other

intellectual property (the Intellectual Property) and any reproductions ofcopyright works in the thesis, for example graphs and tables(Reproductions),

which may be described in this thesis, may not be owned by the author and may

be owned by third parties. Such Intellectual Property and Reproductions cannot

and must not be made available for use without the prior written permission of

the owner(s) of the relevant Intellectual Property and/or Reproductions.

iv. Further information on the conditions under which disclosure, publication and

commercialisation of this thesis, the Copyright and any Intellectual Propertyand/or Reproductions described in it may take place is available in the

University IP Policy (see

http://documents.manchester.ac.uk/DocuInfo.aspx?DocID=487), in any relevant

Thesis restriction declarations deposited in the University Library, The

University Librarys regulations (see

http://www.manchester.ac.uk/library/aboutus/regulations) and in The

Universitys policy on Presentation of Theses.


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To my mother Yumei, my father Baotian, my girl friend Laura and Professor Terzija


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AcknowledgementsThe Research and Development (R&D) project, Wide Area Monitoring, Protection and

Control (WAMPAC) in the Future GB Power System, presented in this thesis is funded

by the National Grid Ltd (UK), Scottish Power Ltd and Scottish Southern Electricity

Ltd.. This R&D project started in April 2008 under the direct supervision of Professor

Vladimir Terzija at the School of Electrical and Electronic Engineering, the University

of Manchester.

First of all, I would like to express my great appreciation to my Ph.D. supervisor,

Professor Terzija, for giving me this great opportunity to be his Ph.D. student. I have no

doubt to claim that this Ph.D. has hugely changed my life, and will benefit me and my

family in the rest of my life. Professor Terzija has been constantly involved in myresearch, and provided me with strong guidance and support all through the project. I

wish to express my gratitude for his constant help.

I also would like to thank my Ph.D. advisor, Professor Peter Crossley and external

project supervisor, John Fitch and Mark Osborn, for their sound advice and kind help.

Thanks to all my friends, in particular, Gustavo Valverde, Jairo Quiros, Pawel Regulski,Peter Wall and Gary Preston for their help and deep friendship.

Lastly, my parents and my girlfriend, Laura Guo, have unwaveringly believed in my

efforts. Their constant support provides me with confidence and courage to ultimately

complete my thesis.


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Chapter 1 Introduction

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1.1 Research Background1.1.1 Power system blackouts

Despite large-scale power system blackouts being very low probability events, their

study is of great interest, due to the immense costs and consequences of such events for

customers, societies and industries [1]. In previous decades, due to economic pressure

from electricity markets and environmental constraints, power system operators have

been forced to operate power transmission systems in highly stressed conditions closer

to the system limits than ever before [1]. In this same period, the number, and size, of

large-scale power system blackouts has increased. For example, the US-Canada

blackout on August 14, 2003 [2] and the Italy blackout on September 28, 2003 [3]

involved more than 100 million customers. Figure 1.1 presents the consequences, in

terms of customers affected, of significant blackouts.

Figure 1.1: Statistics of blackouts: customers affected [1].

It is rare for large-scale power system blackouts to be directly caused by a single large

disturbance. However, a single large disturbance in a stressed system may cause a

series, or cascade, of unplanned and unexpected sequential events. These events will

incrementally increase the stress on the system and force it into a more vulnerable state

of operation. If proper protection and control actions are not taken quickly and properly(e.g. load shedding, reactive power support and controlled islanding), then the system

Customers Affected

010,000,00020,000,00030,000,00040,000,00050,000,00060,000,000

1 9 6 5 , N

E U S

1 9 6 7 , N

E U S

1 9 7 7 ,

N e w Y

o r k

D e c . 1

9 9 4 , W

e s t U S

J u l y 1

9 9 6 , W

e s t U S

A u g . 1

9 9 6 , W

e s t e r n

U S

2 0 0 3 ,

U S - C a

n a d a

2 0 0 3 , I

t a l y

2 0 0 3 ,

S w e d

e n

2 0 0 3 ,

C h i l e

2 0 0 4

G r e e c e


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may experience further cascading events and separate into unplanned islands, or even

completely collapse [4][5][6].

Figure 1.2: Line of separation from the European grid [3].

For example, on September 28 th 2003 a sequence of events, which would lead to the

separation of Italy from the interconnected European Power System, was triggered by

the tripping of a Swiss 380 kV transmission line. The line between Mettlen and Lavorgo

(marked as 1 in Figure 1.2), was tripped off at 03:01 due to a permanent fault. Thistripping meant that other transmission lines began to carry the power that was

previously transferred over the tripped line. This caused a second Swiss 380 kV

transmission line, between Sils and Soazza (marked as 2 in Figure 1.2), to trip at 03:25

due to overload. Combined with insufficient reserve in Italy, the loss of these lines

meant that the levels of overload on the remaining interconnections into Italy quickly

became intolerable. This led to the automatic and, almost, simultaneous tripping of

remaining transmission lines, with the effect that the Italian system was isolated fromthe European network. The Italian power system lost a large amount of the active power

imported from its European neighbours (about 25% of the countrys total load). Such a

large loss of active power caused a sudden frequency drop of approximately 1 Hz to

occur in Italy. Furthermore, this significant loss of power caused multiple Italian

generators to trip for various reasons, e.g. under-frequency relay operation, high

temperature of exhaust gases. Despite additional load shedding, the frequency continued

to decrease and the system collapsed in three minutes [3].


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Whilst it is impossible to develop a solution that completely eliminates the possibility of

a blackout, several measures can be implemented to minimize the probability of a

blackout occurring. For many years, Energy Management System (EMS) has been used

for the on-line monitoring of system conditions and assessment of system security.

Traditional EMS uses measurements with a low-refresh rate (several seconds to oneminute), from a Supervisory Control and Data Acquisition (SCADA) system, to

estimate the system operating condition and to perform off-line system stability studies

[7]. The EMS can provide sufficient information and support for normal steady-state

system operation and to plan the system response to slow changes in the operating

conditions. However, EMS is not capable of capturing system dynamics, particularly

when the system is subjected to large disturbances. In addition, off-line studies cannot

be used to fully anticipate all of the conditions faced by operators. These unplanned

contingencies have the potential to initiate a cascade of events that will lead to a system

blackout.

System Integrity Protection Schemes (SIPSs) are designed to preserve system integrity

after a large disturbance, and restore the system to the normal state when the system is

in an emergency condition [4] [5]. Traditionally, these schemes use the results of offline

studies to determine their actions [7]. These studies are based on the pre-calculated

system behaviour for the assumed operational state of the system. In addition, as

traditional SIPSs only use local or regional (within a power utility) measurements they

lack awareness of the operating conditions in the neighbouring power systems [4] [5].

Consequently, the traditional SIPS may not be sufficient to ensure proper control of any

system instabilities that may occur.

The US-Canadian and Italian blackouts provided very strong evidence that the lack of a

real time dynamic wide area monitoring system and the lack of real-time optimal and

centralized protection and control schemes across a large interconnected network, was

the root cause of these large scale blackouts [2] [3].

Furthermore, attempts to avert climate change through the introduction of renewable

energy policies will force radical changes in future power systems. The most significant

of these is that a large percentage of electrical energy will be generated using renewable

resources (wind, solar and tidal). For example, in the GB power system, the target is forapproximately 45% of electricity to be generated using renewable resources by 2030 [8].

This will prove problematic as electricity generation using renewable resources is


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highly influenced by climatic conditions and the resulting intermittent nature of the

renewable resources. This will make the operation of future power systems more

variable and unpredictable. In addition, renewable energy generation and transmission

requires the support of power electronic technologies such as HVDC and SVC. The use

of these technologies will introduce further complexity and uncertainty into powersystems [9] [10]. The introduction of further variation, complexity and unpredictability

to power systems will dramatically increase the likelihood of large scale power system

blackouts. This will prove a serious problem, as current systems already find themselves

increasingly vulnerable to such blackouts in the absence of a real time wide area

monitoring system.

The development of a real time wide area monitoring system is essential if the future

changes in our power systems do not change the current trend toward an increase in the

number and size of large-scale blackouts. A real time wide area monitoring system will

allow the introduction of optimal, real time protection and control schemes that can be

used to counter the growing threat of large scale blackouts. With the breakthrough made

in the field of Synchronized Measurement Technology (SMT) and the availability of

high-speed communication channels it is now possible to implement a practical real

time wide area monitoring system. These technological developments, combined with

financial support from governments, will allow the emergence of real time, wide area

monitoring, protection and control systems that will be able to ensure the security of

future power systems in the face of an increasingly unstable operational environment.

1.1.2 Wide area monitoring, protection and control

Wide Area Monitoring, Protection, and Control (WAMPAC) involves the use of wide

area synchronized measurements, reliable and high bandwidth communication networks

and advanced centralized protection and control schemes [6]. SMT and related

applications are the essential element, and enabler, of WAMPAC. Presently, Phasor

Measurement Units (PMUs) are the most accurate and advanced synchronized

measurement technology available. They provide voltage and current phasors and

frequency information synchronized with high precision to a common time reference,

the Global Positioning System (GPS). The measurement functions of a PMU are based

on numerical algorithms. These algorithms must be both computationally efficient andsuitable for real-time applications, particularly when the measurements are used to

support dynamic-response applications [6].


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Figure 1.3 shows the main components and structure of a generalized WAMPAC

system. In this system, the necessary synchronized voltage and current phasors are

produced by PMUs. The measurement data from these PMUs is transmitted through a

Wide-Area Network (WAN) and aggregated at one, or more Data Concentrators (DCs).The aggregate data is then stored locally in the DC before being transmitted to the

various Application Software or Servers (ASS) of the different utilities. The main task

performed by the DCs is alignment of the received PMU data; however, the opportunity

also exists to perform additional pre-processing tasks before forwarding the data to ASS

[6].

Utilitys

WAN

PMU_1 PMU_n

Utilitys

WAN

PMU_1 PMU_n Figure 1.3: A Generalized WAMPAC system [6].

The necessity for WAMPAC has gained worldwide acceptance [6], and a number of

WAMPAC systems have been established, or initialized, in different power utilities

throughout the world. For example, a Real Time Dynamic Monitoring System (RTDMS)has been implemented in the Eastern North American bulk power system. A wide area

inter-area oscillation monitoring and control system was established by China South

Power Grid [11]. Other countries, such as Switzerland, Sweden, Denmark, Austria, and

Japan, have developed SMT based applications to improve power system stability [12].


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1.2 Objectives of the Research

Over the coming decades, the biggest change of the GB power system is that a large

percentage of electrical energy will be generated from off-shore wind farms. Majority of

the off-shore wind farms will connect to the power grid with back-to-back HVDC link;hence, they will not provide inertia to the system. Coupled with replacement of the

conventional coal generators with the new wind farms, the inertia of the future UK

power system will be reduced. In addition, a number of Power System Stabilizers (PSSs)

installed on the synchronous generators will be out of service when conventional coal

generators will be replaced by wind farms.

The reduction of system inertia and PSSs will reduce the small signal stability of powersystems, e.g. lightly or unstable damped inter-area oscillations. Therefore, the main

objectives of this research are to propose a WAMPAC system to improve the inter-area

oscillatory stability in the future GB power system and develop solutions to overcome

the challenges that are involved in the initial stage of the GB WAMPAC project.

However, the thesis will not be focused on the assessment of future GB systems with

wind farms, e.g. the system inertia reduction caused by the high penetration of wind

farms connected to the grid over power electronic devices.

The capital investment and logistical effort necessary for the implementation of a

WAMPAC system, particularly for a network with the size and complexity of the GB

power system, mean that it is infeasible to implement it in a single step. Therefore a

well planned roadmap is necessary to ensure the proposed WAMPAC system is

developed in a logical and economic manner. The design of the roadmap should seek to

ensure that the various elements of WAMPAC functionality become available as soon

as is reasonably possible, to maximize the benefit offered to the system operator. This

requirement will lead to the roadmap being separated into multiple stages. Each stage

will focus upon making certain elements of functionality (e.g. system monitoring

applications) available to the operators, whilst ensuring that the actions taken during this

stage are not short term and will lead to needless future redundancy and waste. This

means that each stage will serve as a base for the implementation of more complex

functionality at a future stage.


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The development of such a roadmap is a significant challenge, and as such it constitutes

the primary task for this research project. As different power utilities have different

requirements of WAMPAC, a generic methodology for determining the roadmap is

required. This methodology is based upon an assessment of worldwide experience with

building WAMPAC systems and the analysis of operational challenge of power systems.

Using the roadmap developed from this research, a proposed future GB WAMPAC

system will be created. To support the implement of the proposed WAMPAC system in

the future GB power system, essential WAMPAC applications and algorithms for

improving the inter-area oscillatory stability in the future GB power system are needed

to be developed in this research. In addition, these WAMPAC applications, algorithms

and the WAMPAC systems architecture designed for serving these applications should

be tested in a software package before being implemented in a real system. Therefore,

another main aim of this research is to develop a platform in the DIgSILENT

PowerFactory software package for the evaluation of the proposed future GB

WAMPAC system. Using system models constructed in this software package, the key

factors that will influence the operation of the future GB WAMPAC can be analyzed.

The results obtained through these simulations will serve as a base for future work, e.g.

demonstration of the operation of the GB WAMPAC system in a Real Time Digital

Simulator (RTDS).

The main objectives of this research can be summarized as follows:

1) Review of existing WAMPAC solutions, from applications, system

architecture and technology point of view.

2) Developing a generic methodology for determining the roadmap for the

development of the future GB WAMPAC system.

3) Developing new WAMPAC applications and essential algorithms for

improving the inter-area oscillatory stability in the future GB power system.

4) Establishing a testing platform in DIgSILENT PowerFactory for

demonstrating and evaluating the operation of the GB Wide Area Monitoring

and Control System (WAMCS).


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1.3 Thesis Structure


This chapter briefly introduces the history of power system blackouts and summarises

the root causes of these blackouts. Based on the evaluation of existing solutions for

power system monitoring, protection and control (EMS and SIPSs), and the anticipation

of developments in future power systems, it is determined that a SMT-based WAMPAC

system is the only technology that could be used to reliably manage the next generation

of power systems. The aims of this research are detailed in this chapter along with a list

of the main contributions.

Chapter 2 Synchronized Measurement Technology

This chapter briefly introduces the concept and technology behind synchronized phasor

measurements. This includes the hardware and functionality of SMT devices such as

Phasor measurement Unit (PMU) and Data Concentrator (DC). It will conclude with the

details of major commercial PMUs and DCs.

Chapter 3 Applications and Benefits of Synchronized Measurement Technology

A study of the major applications of SMT will be provided in this chapter as well as an

evaluation of the state of the art and worldwide experience with these applications.

Chapter 4 Architecture of a WAMPAC System

This chapter introduces the architecture of a typical WAMPAC system. This covers the

core components of a WAMPAC system, i.e. the measurement devices, communication

technologies, and their connectivity. The architecture for a future GB WAMPAC

system is then constructed based on international experience with the operation of

WAMPAC.

Chapter 5 The Roadmap to the Future UK WAMPAC System

In this chapter, a methodology for designing a roadmap for the GB WAMPAC project is

introduced. This methodology takes into account the international experience with

WAMPAC project management and the practical challenges faced in a future GB

network. With this methodology, the GBs strategies (both short term and long term) for

the development of a GB WAMPAC system are devised.


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Chapter 6 The Physical Nature of Inter-area Oscillations

The strategy for a GB WAMPAC project has highlighted that a real time inter-area

oscillation monitoring and control system is an important SMT application for the future

GB system. As such, a fundamental study of inter-area oscillations is provided in this

chapter. Two classical methods are introduced to investigate the nature of inter-areaoscillations i.e., nonlinear simulations and modal analysis.

Chapter 7 Inter-area Oscillation Monitoring Using Newton Type Algorithm

In this Chapter, a new inter-area oscillation monitoring method developed for the short

term strategy of the GB WAMPAC project is presented. The core of this novel Wide

Area Monitoring System (WAMS) application is a nonlinear numerical algorithm,

Newton Type Algorithm (NTA) that processes real time oscillatory signals to estimate

the dominant inter-area oscillatory mode. Two data sets are tested using the new

algorithm, one based on simulated models and the other based on real-life data records.

Chapter 8 The Application of Power Electronic Devices for Damping Inter-area

oscillations

In this Chapter, several closed loop control schemes that use power electronics devices

i.e. HVDC, TCSC and SVC to stabilize inter-area oscillations are presented. A modal

analysis based linear control theory is used for tuning the parameters of the damping

controllers; and then these damping controllers are tested through dynamic simulation in

a typical two-area system model.

Chapter 9 Wide Area Monitoring and Control System in a future GB Power

System

In this Chapter, a proposed Wide Area Monitoring and Control System (WAMCS) for

the future GB power system is presented. This WAMCS is designed to enhance the

small signal stability of the future GB power system, i.e. , improve the damping of the

inter-area oscillatory mode between Scotland and England. The operation of the

WAMCS will be demonstrated in the DIgSILENT software package. Some key factors

that will influence the operation of the future GB WAMCS will be discussed, including

the time delay involved in the wide area data transmission, and the reactions between

the new wide area control system and conventional Power System Stabilizers (PSSs).


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Chapter 10 Conclusions and Future Work

The last chapter presents the major conclusions of this research and suggests further

directions for future research.

1.4 Main Contributions of This Research

1) Review of the state of the art of SMT applications and the worldwide experience

of the operation of WAMPAC systems.

2) Construction of an architecture prototype for the future GB WAMPAC system,

based on the international experience with WAMPAC and the likely

characteristics of the future GB power system.

3) Introduction of a methodology for designing a roadmap to implement

WAMPAC in the future GB power system.

4) Proposal of the UKs strategies (short term and long term) to guide the

development of the future GB WAMPAC system.

5) Development of a novel nonlinear numerical algorithm, Newton Type Algorithm

(NTA), for identifying dominant inter-area oscillation mode.

6) Modelling of Power electronic devices, HVDC, TCSC and SVC.

7) Proposal of a detailed procedure for the design of a wide area inter-area

oscillation damping control system using power electronic devices, i.e. HVDC,

TCSC and SVC.

8) Establishment of a testing platform in the DIgSILENT software package for

demonstrating and evaluating the operation of the GB Wide Area Monitoring

and Control System (WAMCS).


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Chapter 2 Synchronized Measurement

Technology

2.1 Introduction

The voltage phase angles at the buses in an electrical power transmission network have

always been of special interest to power system operators. It is well-known that active

power flow over a transmission line is nearly proportional to the sine of the angle

difference between the voltages at the two terminals of the transmission line. As many

of the planning and operational considerations in electrical power systems are directly

concerned with the active power flow, measuring voltage angle differences across the

transmission line has been of concern for many years [14].

Consider a pure sinusoidal signal as shown in Figure 2.1. If the observation of the signal

begins at the time t = 0 s, the signal can be represented by a complex number with a

magnitude equal to the Root Mean Square (RMS) value of the signal and with a phase

angle. In a digital measuring system, the samples of the waveform in one period are

collected, and then the fundamental frequency component of the signal can be

calculated by using the following equation [14]:

=

= N

k

N k jk e x N

X 1

/22 (2.1)

where N is the total number of samples in one period, X is the phasor representing the

sinusoidal signal, and k x is k th sample of the signal. In a real measurement system, the

signal is continuously sampled and each time a new sample is acquired a new phasor is

produced as the data window is moved to include the new sample. The most efficient

method for dealing with continuous monitoring of the input waveforms is to use a

recursive form of the phasor equation [15].


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m X

Figure 2.1: Phasor representation of a sinusoidal signal [16].

For the evaluation of the performance of a real power system, the positive sequence

voltages and currents are far more useful than the single phase quantities. Positive-

sequence voltages of a network constitute the st

wide area monitoring, protection and control in future great britain power system

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