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Integration of Distributed Generation in the Power System

ISBN: 978-1-118-02902-2
528 pages
August 2011, Wiley-IEEE Press
Integration of Distributed Generation in the Power System (111802902X) cover image
The integration of new sources of energy like wind power, solar-power, small-scale generation, or combined heat and power in the power grid is something that impacts a lot of stakeholders: network companies (both distribution and transmission), the owners and operators of the DG units, other end-users of the power grid (including normal consumers like you and me) and not in the least policy makers and regulators.

There is a lot of misunderstanding about the impact of DG on the power grid, with one side (including mainly some but certainly not all, network companies) claiming that the lights will go out soon, whereas the other side (including some DG operators and large parks of the general public) claiming that there is nothing to worry about and that it's all a conspiracy of the large production companies that want to protect their own interests and keep the electricity price high.

The authors are of the strong opinion that this is NOT the way one should approach such an important subject as the integration of new, more environmentally friendly, sources of energy in the power grid. With this book the authors aim to bring some clarity to the debate allowing all stakeholders together to move to a solution. This book will introduce systematic and transparent methods for quantifying the impact of DG on the power grid.

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PREFACE xi

ACKNOWLEDGMENTS xiii

CHAPTER 1 INTRODUCTION 1

CHAPTER 2 SOURCES OF ENERGY 6

2.1 Wind Power 7

2.1.1 Status 7

2.1.2 Properties 7

2.1.3 Variations in Wind Speed 8

2.1.4 Variations in Production Capacity 10

2.1.5 The Weibull Distribution of Wind Speed 20

2.1.6 Power Distribution as a Function of the Wind Speed 22

2.1.7 Distribution of the Power Production 26

2.1.8 Expected Energy Production 29

2.2 Solar Power 30

2.2.1 Status 30

2.2.2 Properties 31

2.2.3 Space Requirements 32

2.2.4 Photovoltaics 33

2.2.5 Location of the Sun in the Sky 35

2.2.6 Cloud Coverage 39

2.2.7 Seasonal Variations in Production Capacity 42

2.2.8 Fast Variations with Time 46

2.3 Combined Heat-and-Power 50

2.3.1 Status 50

2.3.2 Options for Space Heating 51

2.3.3 Properties 52

2.3.4 Variation in Production with Time 53

2.3.5 Correlation Between CHP and Consumption 56

2.4 Hydropower 59

2.4.1 Properties of Large Hydro 60

2.4.2 Properties of Small Hydro 61

2.4.3 Variation with Time 61

2.5 Tidal Power 65

2.6 Wave Power 66

2.7 Geothermal Power 67

2.8 Thermal Power Plants 68

2.9 Interface with the Grid 71

2.9.1 Direct Machine Coupling with the Grid 72

2.9.2 Full Power Electronics Coupling with the Grid 73

2.9.3 Partial Power Electronics Coupling to the Grid 75

2.9.4 Distributed Power Electronics Interface 79

2.9.5 Impact of the Type of Interface on the Power System 80

2.9.6 Local Control of Distributed Generation 81

CHAPTER 3 POWER SYSTEM PERFORMANCE 84

3.1 Impact of Distributed Generation on the Power System 84

3.1.1 Changes Taking Place 84

3.1.2 Impact of the Changes 85

3.1.3 How Severe Is This? 86

3.2 Aims of the Power System 87

3.3 Hosting Capacity Approach 88

3.4 Power Quality 91

3.4.1 Voltage Quality 92

3.4.2 Current Quality 92

3.4.3 Multiple Generator Tripping 93

3.5 Voltage Quality and Design of Distributed Generation 95

3.5.1 Normal Operation; Variations 96

3.5.2 Normal Events 96

3.5.3 Abnormal Events 97

3.6 Hosting Capacity Approach for Events 98

3.7 Increasing the Hosting Capacity 100

CHAPTER 4 OVERLOADING AND LOSSES 102

4.1 Impact of Distributed Generation 102

4.2 Overloading: Radial Distribution Networks 105

4.2.1 Active Power Flow Only 105

4.2.2 Active and Reactive Power Flow 108

4.2.3 Case Study 1: Constant Production 109

4.2.4 Case Study 2: Wind Power 110

4.2.5 Case Study 3: Wind Power with Induction Generators 111

4.2.6 Case Study 4: Solar Power with a Hotel 111

4.2.7 Minimum Consumption 115

4.3 Overloading: Redundancy and Meshed Operation 116

4.3.1 Redundancy in Distribution Networks 116

4.3.2 Meshed Operation 117

4.3.3 Redundancy in Meshed Networks 119

4.4 Losses 122

4.4.1 Case Study 1: Constant Production 124

4.4.2 Case Study 2: Wind Power 125

4.5 Increasing the Hosting Capacity 126

4.5.1 Increasing the Loadability 126

4.5.2 Building New Connections 127

4.5.3 Intertrip Schemes 127

4.5.4 Advanced Protection Schemes 128

4.5.5 Energy Management Systems 131

4.5.6 Power Electronics Approach 133

4.5.7 Demand Control 136

4.5.8 Risk-Based Approaches 137

4.5.9 Prioritizing Renewable Energy 139

4.5.10 Dynamic Loadability 139

CHAPTER 5 VOLTAGE MAGNITUDE VARIATIONS 141

5.1 Impact of Distributed Generation 141

5.2 Voltage Margin and Hosting Capacity 144

5.2.1 Voltage Control in Distribution Systems 144

5.2.2 Voltage Rise Owing to Distributed Generation 146

5.2.3 Hosting Capacity 147

5.2.4 Induction Generators 149

5.2.5 Measurements to Determine the Hosting Capacity 150

5.2.6 Estimating the Hosting Capacity Without Measurements 151

5.2.7 Choosing the Overvoltage Limit 153

5.2.8 Sharing the Hosting Capacity 156

5.3 Design of Distribution Feeders 156

5.3.1 Basic Design Rules 156

5.3.2 Terminology 157

5.3.3 An Individual Generator Along a Medium-Voltage Feeder 158

5.3.4 Low-Voltage Feeders 163

5.3.5 Series and Shunt Compensation 166

5.4 A Numerical Approach to Voltage Variations 168

5.4.1 Example for Two-stage Boosting 168

5.4.2 General Expressions for Two-Stage Boosting 170

5.4.3 Single-Stage Boosting 171

5.4.4 Microgeneration 171

5.5 Tap Changers with Line-Drop Compensation 174

5.5.1 Transformer with One Single Feeder 174

5.5.2 Adding a Generator 175

5.5.3 Calculating the Hosting Capacity 177

5.5.4 Multiple Feeders from the Same Transformer 178

5.6 Probabilistic Methods for Design of Distribution Feeders 181

5.6.1 Need for Probabilistic Methods 181

5.6.2 The System Studied 181

5.6.3 Probability Density and Distribution Functions 182

5.6.4 Distributions of Functions of Random Variables 182

5.6.5 Mean and Standard Deviation 183

5.6.6 Normal Distributions 184

5.6.7 Stochastic Calculations Using Measurements 185

5.6.8 Generation with Constant Production 190

5.6.9 Adding Wind Power 191

5.7 Statistical Approach to Hosting Capacity 192

5.8 Increasing the Hosting Capacity 197

5.8.1 New or Stronger Feeders 198

5.8.2 Alternative Methods for Voltage Control 199

5.8.3 Accurate Measurement of the Voltage Magnitude Variations 200

5.8.4 Allowing Higher Overvoltages 201

5.8.5 Risk-Based Approach to Overvoltages 202

5.8.6 Overvoltage Protection 203

5.8.7 Overvoltage Curtailment 204

5.8.8 Dynamic Voltage Control 209

5.8.9 Compensating the Generator’s Voltage Variations 210

5.8.10 Distributed Generation with Voltage Control 211

5.8.11 Coordinated Voltage Control 218

5.8.12 Increasing the Minimum Load 221

CHAPTER 6 POWER QUALITY DISTURBANCES 223

6.1 Impact of Distributed Generation 223

6.2 Fast Voltage Fluctuations 225

6.2.1 Fast Fluctuations in Wind Power 226

6.2.2 Fast Fluctuations in Solar Power 228

6.2.3 Rapid Voltage Changes 228

6.2.4 Very Short Variations 230

6.2.5 Spread of Voltage Fluctuations 233

6.3 Voltage Unbalance 237

6.3.1 Weaker Transmission System 237

6.3.2 Stronger Distribution System 238

6.3.3 Large Single-Phase Generators 240

6.3.4 Many Single-Phase Generators 242

6.4 Low-Frequency Harmonics 247

6.4.1 Wind Power: Induction Generators 248

6.4.2 Generators with Power Electronics Interfaces 250

6.4.3 Synchronous Generators 251

6.4.4 Measurement Example 252

6.4.5 Harmonic Resonances 254

6.4.6 Weaker Transmission Grid 266

6.4.7 Stronger Distribution Grid 267

6.5 High-Frequency Distortion 270

6.5.1 Emission by Individual Generators 271

6.5.2 Grouping Below and Above 2 kHz 274

6.5.3 Limits Below and Above 2 kHz 275

6.6 Voltage Dips 278

6.6.1 Synchronous Machines: Balanced Dips 279

6.6.2 Synchronous Machines: Unbalanced Dips 282

6.6.3 Induction Generators and Unbalanced Dips 287

6.7 Increasing the Hosting Capacity 291

6.7.1 Strengthening the Grid 292

6.7.2 Emission Limits for Generator Units 292

6.7.3 Emission Limits for Other Customers 293

6.7.4 Higher Disturbance Levels 294

6.7.5 Passive Harmonic Filters 296

6.7.6 Power Electronics Converters 296

6.7.7 Reducing the Number of Dips 297

6.7.8 Broadband and High-Frequency Distortion 298

CHAPTER 7 PROTECTION 299

7.1 Impact of Distributed Generation 299

7.2 Overcurrent Protection 303

7.2.1 Upstream and Downstream Faults 303

7.2.2 Hosting Capacity 304

7.2.3 Fuse–Recloser Coordination 305

7.2.4 Inverse-Time Overcurrent Protection 308

7.3 Calculating the Fault Currents 310

7.3.1 Upstream Faults 310

7.3.2 Downstream Faults 320

7.3.3 Induction Generators, Power Electronics, and Motor Load 325

7.4 Calculating the Hosting Capacity 326

7.5 Busbar Protection 333

7.6 Excessive Fault Current 334

7.7 Generator Protection 336

7.7.1 General Requirements 336

7.7.2 Insufficient Fault Current 337

7.7.3 Noncontrolled Island Operation 340

7.7.4 Islanding Detection 342

7.7.5 Harmonic Resonance During Island Operation 354

7.7.6 Protection Coordination 357

7.8 Increasing the Hosting Capacity 358

7.8.1 Dedicated Feeder 359

7.8.2 Increased Generator Impedance 360

7.8.3 Generator Tripping 360

7.8.4 Time-Current Setting 361

7.8.5 Adding an Additional Circuit Breaker 362

7.8.6 Directional Protection 362

7.8.7 Differential or Distance Protection 363

7.8.8 Advanced Protection Schemes 363

7.8.9 Islanding Protection 365

CHAPTER 8 TRANSMISSION SYSTEM OPERATION 367

8.1 Impact of Distributed Generation 367

8.2 Fundamentals of Transmission System Operation 371

8.2.1 Operational Reserve and (N – 1) Criterion 372

8.2.2 Different Types of Reserve 373

8.2.3 Automatic or Manual Secondary Control 375

8.3 Frequency Control, Balancing, and Reserves 376

8.3.1 The Need for Reserves 376

8.3.2 Primary Control and Reserves 377

8.3.3 Secondary Control and Reserves 382

8.3.4 Tertiary Control and Reserves 389

8.3.5 Impact of Decay in Production on Reserves 393

8.4 Prediction of Production and Consumption 398

8.5 Restoration after a Blackout 403

8.6 Voltage Stability 405

8.6.1 Short-Term Voltage Stability 406

8.6.2 Long-Term Voltage Stability 410

8.7 Kinetic Energy and Inertia Constant 417

8.8 Frequency Stability 422

8.9 Angular Stability 425

8.9.1 One Area Against the Infinite Grid 425

8.9.2 Impact of Distributed Generation: Before the Fault 429

8.9.3 Impact of Distributed Generation: During the Fault 430

8.9.4 Impact of Distributed Generation: Critical Fault-Clearing Time 431

8.9.5 Impact of Distributed Generation: After the Fault 435

8.9.6 Impact of Distributed Generation: Importing Area 436

8.10 Fault Ride-Through 437

8.10.1 Background 437

8.10.2 Historical Cases 439

8.10.3 Immunity Requirements 440

8.10.4 Achieving Fault Ride-Through 445

8.11 Storage 447

8.12 HVDC and Facts 451

8.13 Increasing the Hosting Capacity 457

8.13.1 Alternative Scheduling of Reserves 457

8.13.2 Increasing the Transfer Capacity 458

8.13.3 Large-Scale Energy Storage 458

8.13.4 Distributed Generation as Reserve 459

8.13.5 Consumption as Reserve 460

8.13.6 Requirements on Distributed Generation 461

8.13.7 Reactive Power Control 461

8.13.8 Probabilistic Methods 462

8.13.9 Development of Standard Models for Distributed Generation 464

CHAPTER 9 CONCLUSIONS 465

BIBLIOGRAPHY 471

INDEX 497

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MATH H.J. BOLLEN, PhD, is Senior Specialist with STRI AB, Gothenburg, Sweden; Professor in Electric Power Engineering at Luleå University of Technology, Skellefteå, Sweden; and a technical expert with the Energy Markets Inspectorate in Eskilstuna, Sweden. He is a Fellow of the IEEE.

FAINAN HASSAN, PhD, is with the Alstom Grid (previously Areva T&D), Research & Technology Centre, Stafford, United Kingdom. A member of the IEEE, she has also worked as a seniorengineer for STRI AB, Gothenburg, Sweden.

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The author’s organization of the book is superb, and the write-up with appropriate examples is very clear.  The book will be useful to those who have good prior knowledge in power engineering including power electronics and renewable energy sources.  The book offers a very comprehensive discussion of modern power system operation with distributed generation by  renewable energy sources.  It describes sources of energy, power system performance, overloading and losses, voltage variations, power quality disturbances, faults and protection, and transmission  with distributed generation. Many examples are given with emphasis of European system. It is an excellent reference book for modern power engineers.
—Dr. Bimal K. Bose, Condra Chair of Excellence/Emeritus in Power Electronics, University of Tennessee
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