wind energy and control

S e c o n d E d i t i o n

ELECTRICAL MACHINES

with MATLAB*

TURAN GONEN

CRC Press Taylor & Francis Group

Boca Raton London New York

CRC Press is an imprint of the Taylor & Francis Group, an informa business

Contents Preface to the First Edition xiii Preface to the Second Edition xv Acknowledgments xvii Author xix

Chapter 1 Basic Concepts 1

1.1 Introduction 1 1.2 Distribution System 4 1.3 Impact of Dispersed Storage and Generation 5 1.4 Brief Overview of Basic Electrical Machines 7 1.5 Real and Reactive Powers in Single-Phase AC Circuits 9 Problems 14

Chapter 2 Three-Phase Circuits 17

2.1 Introduction 17 2.2 Three-Phase Systems 17

2.2.1 Ideal Three-Phase Power Sources 18 2.2.1.1 Wye-Connected Ideal Three-Phase Source 21 2.2.1.2 Delta-Connected Ideal Three-Phase Source 24

2.2.2 Balanced Three-Phase Loads 24 2.3 Unbalanced Three-Phase Loads 33 2.4 Measurement of Average Power in Three-Phase Circuits 37 2.5 Power Factor Correction 41 Problems 44

Chapter 3 Magnetic Circuits 53

3.1 Introduction 53 3.2 Magnetic Field of Current-Carrying Conductors 53 3.3 Ampere's Magnetic Circuital Law 56 3.4 Magnetic Circuits 58 3.5 Magnetic Circuit with Air Gap 66 3.6 Brief Review of Ferromagnetism 68 3.7 Magnetic Core Losses 72

3.7.1 Hysteresis Loss 72 3.7.2 Eddy-Current Loss 72

3.8 How to Determine Flux for a Given MMF 81 3.8.1 Trial-and-Error Method 82 3.8.2 Graphical Method 82 3.8.3 Magnetization Curve Method 83

3.9 Permanent Magnets 85 Problems 88

V

vi Contents

Chapter 4 Transformers 93

4.1 Introduction 93 4.2 Transformer Construction 97 4.3 Brief Review of Faraday's and Lenz's Laws of Induction 98 4.4 Ideal Transformer 101

4.4.1 Dot Convention in Transformers 104 4.4.2 Impedance Transfer through a Transformer 105 4.4.3 Relationship between Input and Output Powers of an

Ideal Transformer 107 4.5 Real Transformer 113 4.6 Approximate Equivalent Circuit of a Real Transformer 116 4.7 Determination of Equivalent-Circuit Parameters 121

4.7.1 Open-Circuit Test 121 4.7.2 Short-Circuit Test 123

4.8 Transformer Nameplate Rating 124 4.9 Performance Characteristics of a Transformer 129

4.9.1 Voltage Regulation of a Transformer 129 4.9.2 Transformer Efficiency 134

4.10 Three-Phase Transformers 138 4.11 Three-Phase Transformer Connections 140 4.12 Autotransformers 146 4.13 Three-Winding Transformers 152 4.14 Instrument Transformers 153 4.15 Inrush Current 154 Problems 156

Chapter 5 Electromechanical Energy Conversion Principles 165

5.1 Introduction 165 5.2 Fundamental Concepts 165 5.3 Electromechanical Energy Conversion 175

5.3.1 Field Energy 177 5.3.2 Magnetic Force 183 5.3.3 Energy and Coenergy 185 5.3.4 Magnetic Force in a Saturable System 185

5.4 Study of Rotating Machines 188 5.5 Singly Excited Rotating Systems 188 5.6 Multiply Excited Rotating Systems 193 5.7 Cylindrical Machines 197

5.7.1 Single-Phase Synchronous Machine 199 5.7.2 Single-Phase Induction Machine 199

5.8 Force Produced on a Conductor 200 5.9 Induced Voltage on a Conductor Moving in a Magnetic Field 202 Problems 204

Chapter 6 Induction Machines 207

6.1 Introduction 207 6.2 Construction of Induction Motors 211

Contents vii

6.3 Rotating Magnetic Field Concept 213 6.3.1 Graphical Method 214 6.3.2 Analytical Method 216

6.4 Induced Voltages 219 6.5 Concept of Rotor Slip 220 6.6 Effects of Slip on the Frequency and Magnitude of Induced

Voltage of the Rotor 222 6.7 Equivalent Circuit of an Induction Motor 225

6.7.1 Stator Circuit Model 225 6.7.2 Rotor-Circuit Model 226 6.7.3 Complete Equivalent Circuit 228 6.7.4 Approximate Equivalent Circuit 229

6.8 Performance Calculations 230 6.9 Equivalent Circuit at Start-Up 236 6.10 Determination of Power and Torque by Use of Thevenin's

Equivalent Circuit 241 6.11 Performance Characteristics 243 6.12 Control of Motor Characteristics by Squirrel-Cage Rotor Design 249 6.13 Starting of Induction Motors 251

6.13.1 Direct-on-Line Starting 252 6.13.2 Reduced-Voltage Starting 253 6.13.3 Current Limiting by Series Resistance or Impedance 254

6.14 Speed Control 259 6.15 Tests to Determine Equivalent-Circuit Parameters 260

6.15.1 No-Load Test 261 6.15.2 DC Test 261 6.15.3 Blocked-Rotor Test 262

Problems 267

Chapter 7 Synchronous Machines 273

7.1 Introduction 273 7.2 Construction of Synchronous Machines 273 7.3 Field Excitation of Synchronous Machines 276 7.4 Synchronous Speed 277 7.5 Synchronous Generator Operation 278 7.6 Equivalent Circuits 282 7.7 Synchronous Motor Operation 288 7.8 Power and Torque Characteristics 288 7.9 Stiffness of Synchronous Machines 293 7.10 Effect of Changes in Excitation 294

7.10.1 Synchronous Machine Connected to an Infinite Bus 294 7.10.2 Synchronous Generator Operating Alone 297

7.11 Use of Damper Windings to Overcome Mechanical Oscillations 298 7.12 Starting of Synchronous Motors 298 7.13 Operating a Synchronous Motor as a Synchronous Condenser 299 7.14 Operating a Synchronous Motor as a Synchronous Reactor 300 7.15 Tests to Determine Equivalent-Circuit Parameters 301

7.15.1 Open-Circuit Test 301 7.15.2 Short-Circuit Test 302

viii Contents

7.15.3 DC lest 302 7.15.4 Unsaturated Synchronous Reactance 303 7.15.5 Saturated Synchronous Reactance 304 7.15.6 Short-Circuit Ratio 304

7.16 Capability Curve of Synchronous Machine 305 7.17 Parallel Operation of Synchronous Generators 306 Problems 308

Chapter 8 Direct-Current Machines 313

8.1 Introduction 313 8.2 Constructional Features 313 8.3 Brief Review of Armature Windings 316 8.4 Elementary DC Machine 318 8.5 Armature Voltage 319 8.6 Methods of Field Excitation 323 8.7 Armature Reaction 323 8.8 Commutation 325 8.9 Compensating Windings 327 8.10 Magnetization Curve 328 8.11 DC Generators 332 8.12 Separately Excited Generator 332 8.13 Self-Excited Shunt Generator 333 8.14 Series Generator 335 8.15 Compound Generator 336 8.16 Voltage Regulation 337 8.17 Developed Power 341 8.18 Developed Torque 342 8.19 Power Flow and Efficiency 343 8.20 DC Motor Characteristics 348

8.20.1 Speed Regulation 348 8.20.2 Speed-Current Characteristic 349 8.20.3 Speed-Torque Characteristic 350 8.20.4 Torque-Current Characteristic 351 8.20.5 Internal Generated Voltage-Current Characteristic 351

8.21 Control of DC Motors 355 8.22 DC Motor Starting 358 8.23 DC Motor Braking 364 Problems 366

Chapter 9 Single-Phase and Special-Purpose Motors 371

9.1 Introduction 371 9.2 Single-Phase Induction Motors 371

9.2.1 Equivalent Circuit 374 9.2.2 Performance Analysis 374

9.3 Starting of Single-Phase Induction Motors 380 9.4 Classification of Single-Phase Induction Motors 381

9.4.1 Split-Phase Motors 381 9.4.2 Capacitor-Start Motors 382 9.4.3 Capacitor-Run Motors 383

Contents ix

9.4.4 Capacitor-Start Capacitor-Run Motors 384 9.4.5 Shaded-Pole Motors 384

9.5 Universal Motors 387 9.6 Single-Phase Synchronous Motors 390

9.6.1 Reluctance Motors 390 9.6.2 Hysteresis Motors 391 9.6.3 Stepper Motors 392

9.7 Subsynchronous Motors 394 9.8 Permanent-Magnet DC Motors 394 Problems 398

Chapter 10 Transients and Dynamics of Electric Machines 401

10.1 Introduction 401 10.2 DC Machines 401 10.3 Separately Excited DC Generator 401

10.3.1 Field-Circuit Transient 403 10.3.2 Armature-Circuit Transient 404

10.4 Separately Excited DC Motor 408 10.5 Synchronous Generator Transients 413 10.6 Short-Circuit Transients 413 10.7 Transient Stability 419 10.8 Swing Equation 420 Problems 424

Chapter 11 Renewable Energy 427

11.1 Introduction 427 11.2 Renewable Energy 428 11.3 Impact of Dispersed Storage and Generation 429 11.4 Integrating Renewables into Power Systems 429 11.5 Distributed Generation 430 11.6 Renewable Energy Penetration 431 11.7 Active Distribution Network 431 11.8 Concept of Microgrid 431 References 434

Chapter 12 Wind Energy and Wind Energy Conversion System (WECS) 435

12.1 Introduction 435 12.2 Advantages and Disadvantages of Wind Energy Conversion Systems 436

12.2.1 Advantages of a Wind Energy Conversion System 437 12.2.2 Disadvantages of a Wind Energy Conversion System 437

12.3 Categories of Wind Turbines 437 12.4 Visual Impact of Wind Turbines 441 12.5 Types of Generators Used in Wind Turbines 442 12.6 Wind Turbine Operating Systems 444

12.6.1 Constant-Speed Wind Turbines 444 12.6.2 Variable-Speed Wind Turbine System 445

12.7 Meteorology of Wind 446 12.8 Power in the Wind 449

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12.9 Effects of a Wind Force 452 12.10 Impact of Tower Height on Wind Power 453 12.11 Wind Measurements 455 12.12 Characteristics of a Wind Generator 456 12.13 Efficiency and Performance 458 12.14 Efficiency of a Wind Turbine 461

12.14.1 Generator Efficiency 461 12.14.2 Gearbox 461 12.14.3 Overall Efficiency 462

12.15 Other Factors to Define the Efficiency 462 12.16 Grid Connection 464 12.17 Some Further Issues Related to Wind Energy 465 12.18 Development of Transmission System for Wind Energy in the United

States 466 12.19 Energy Storage 466 12.20 Wind Power Forecasting 467 Problems 469 References 469

Chapter 13 Solar Energy Systems 471

13.1 Introduction 471 13.2 Crystalline Silicon 472 13.3 Effect of Sunlight on Solar Cell's Performance 476 13.4 Effects of Changing Strength of the Sun on a Solar Cell 477 13.5 Temperature's Effect on Cell Characteristics 480 13.6 Efficiency of Solar Cells 482 13.7 Interconnection of Solar Cells 483 13.8 Overall System Configuration 485 13.9 Thin-Film PV 487 13.10 Concentrating PV 488 13.11 PV Balance of Systems 488 13.12 Types of Conversion Technologies 488 13.13 Linear CSP Systems 489 13.14 Power Tower CSP Systems 489 13.15 Dish/Engine CSP Systems 489 13.16 PV Applications 490

13.16.1 Utility-Interactive PV Systems 490 13.16.2 Stand-Alone PV Systems 490

Problems 490 References 491

Chapter 14 Energy Storage Systems 493

14.1 Introduction 493 14.2 Storage Systems 493 14.3 Storage Devices 494

14.3.1 Large Hydro 494 14.3.2 Compressed-Air Storage 495 14.3.3 Pumped Hydro 495 14.3.4 Hydrogen 496

Contents xi

14.3.5 High-Power Flow Batteries 496 14.3.6 High-Power Fly wheels 497 14.3.7 High-Power Supercapacitors 497 14.3.8 Superconducting Magnetic Energy Storage 497 14.3.9 Heat or Cold Storage 498

14.4 Battery Types 499 14.4.1 Secondary Batteries 499 14.4.2 Sodium-Sulfur Batteries 499 14.4.3 Flow Battery Technology 500

14.4.3.1 Zinc-Bromine Flow Battery 501 14.4.3.2 Vanadium Redox Flow Battery 501

14.4.4 Lithium-Ion Batteries 501 14.4.4.1 Lithium Titanate Batteries 501 14.4.4.2 Lithium Iron Phosphate Batteries 501

14.4.5 Lead-Acid Batteries 501 14.4.5.1 Advanced Lead-Acid Batteries 502

14.4.6 Nickel-Cadmium Batteries 502 14.5 Operational Problems in Battery Usage 502 14.6 Fuel Cells 503

14.6.1 Types of Fuel Cells 505 14.6.1.1 Polymer Electrolyte Membrane 506 14.6.1.2 Phosphoric Acid Fuel Cell 506 14.6.1.3 Molten Carbonate Fuel Cell 507 14.6.1.4 Solid Oxide Fuel Cell 507

References 508

Chapter 15 The Smart Grid 509

15.1 Introduction 509 15.2 Need for Establishment of Smart Grid 512 15.3 Roots of the Motivation for the Smart Grid 513 15.4 Distribution Automation 516 15.5 Active Distribution Networks 517 15.6 Volt/Var Control in Distribution Networks 517

15.6.1 Traditional Approach to Volt/Var Control in the Distribution Networks 517

15.6.2 SCADA Approach to Control Volt/Var in the Distribution Networks 519

15.6.3 Integrated Volt/Var Control Optimization 521 15.7 Existing Electric Power Grid 523 15.8 Supervisory Control and Data Acquisition 524 15.9 Advanced SCADA Concepts 526 15.10 Substation Controllers 527 15.11 Advanced Developments for Integrated Substation Automation 528 15.12 Evolution of Smart Grid 531 15.13 Smart Microgrids 534 15.14 Topology of aMicrogrid 535 15.15 Topology of a Smart Grid 535 15.16 Standards of Smart Grids 535 15.17 Existing Challenges to the Application of the Concept of Smart Grids 537 References 538

xii Contents

Appendix A: Brief Review of Phasors 539

Appendix B: Per-Unit System 547

Appendix C: Salient-Pole Synchronous Machines 569

Appendix D: Unit Conversions from the English System to SI System 577

Appendix E: Unit Conversions from the SI System to English System 579

Appendix F: Stator Windings 581

Appendix G: Glossary for Electrical Machines Terminology 585

Answers to Selected Problems 615

Bibliography 619

Index 623