Grid Integration of Wind Energy

Preface xi

Notation xiii

1 Wind Energy Power Plants 1

1.1 Wind Turbine Structures 1

1.2 A Brief History 4

1.3 Milestones of Development 5

1.4 Functional Structures of Wind Turbines 20

References 30

2 Wind Energy Conversion Systems 31

2.1 Drive Torque and Rotor Power 31

2.1.1 Inputs and outputs of a wind turbine 31

2.1.2 Power extraction from the airstream 32

2.1.3 Determining power or driving torque by the blade element method 34

2.1.4 Simplifying the computation method 38

2.1.5 Modeling turbine characteristics 40

2.2 Turbines 46

2.2.1 Hub and turbine design 50

2.2.2 Rotor blade geometry 51

2.3 Power Control by Turbine Manipulation 57

2.3.1 Turbine yawing 57

2.3.2 Rotor blade pitch variation 67

2.3.3 Limiting power by stall control 97

2.3.4 Power control using speed variation 100

2.4 Mechanical Drive Trains 102

2.5 System Data of a Wind Power Plant 108

2.5.1 Turbine and drive train data 108

2.5.2 Machine and tower masses 110

2.5.3 Machine costs 111

References 116

3 Generating Electrical Energy from Mechanical Energy 119

3.1 Constraints and Demands on the Generator 119

3.2 Energy Converter Systems 122

3.2.1 Asynchronous generator construction 125

3.2.2 Synchronous generator construction 126

3.3 Operational Ranges of Asynchronous and Synchronous Machines 126

3.4 Static and Dynamic Torque 132

3.4.1 Static torque 133

3.4.2 Dynamic torque 147

3.5 Generator Simulation 154

3.5.1 Synchronous machines 155

3.5.2 Asynchronous machines 160

3.6 Design Aspects 161

3.6.1 Asynchronous generators 162

3.6.2 Synchronous generators for gearless plants 174

3.6.3 Multi-generator concept (Dissertation A. Ezzahraoui) 187

3.6.4 Ring generator with magnetic bearings (Dissertation K. Messol) 194

3.6.5 Compact superconductive and other new generator concepts 197

3.7 Machine Data 199

3.7.1 Mass and cost relationships 200

3.7.2 Characteristic values of asynchronous machines 202

3.7.3 Characteristic values of synchronous machines 204

References 208

4 The Transfer of Electrical Energy to the Supply Grid 210

4.1 Power Conditioning and Grid Connection 210

4.1.1 Converter systems 212

4.1.2 Power semiconductors for converters 215

4.1.3 Functional characteristics of power converters 218

4.1.4 Converter designs 222

4.1.5 Indirect converter 223

4.1.6 Electromagnetic compatibility (EMC) 236

4.1.7 Protective measures during power conditioning 237

4.2 Grid Protection 238

4.2.1 Fuses and grid disconnection 239

4.2.2 Short-circuiting power 239

4.2.3 Increase of short-circuit power 242

4.2.4 Isolated operation and rapid auto-reclosure 245

4.2.5 Overvoltages in the event of grid faults 247

4.3 Grid Effects 247

4.3.1 General compatibility and interference 247

4.3.2 Output behavior of wind power plants 248

4.3.3 Voltage response in grid supply 260

4.3.4 Harmonics and subharmonics 271

4.3.5 Voltage faults and the fault-ride-through (FRT) 279

4.4 Resonance Effects in the Grid During Normal Operation 284

4.5 Remedial Measures against Grid Effects and Grid Resonances 290

4.5.1 Filters 290

4.5.2 Filter design 292

4.5.3 Function of harmonic absorber filters and compensation units 293

4.5.4 Grid-specific filter layout 294

4.5.5 Utilizing compensating effects 297

4.6 Grid Control and Protection 300

4.6.1 Supply by wind turbines 300

4.6.2 Grid support and grid control with wind turbines and other renewable systems 301

4.6.3 Central reactive power control 305

4.6.4 System services and operation 308

4.6.5 Connection of wind turbine to the transmission grid 310

4.7 Grid Connection Rules 311

4.8 Grid Connection in the Offshore Region 317

4.8.1 Offshore wind farm properties 317

4.8.2 Stationary and dynamic behavior of offshore wind farms 319

4.8.3 Wind farm and cluster formation at sea and grid connection 319

4.8.4 Electrical energy transmission to the mainland 323

4.8.5 Reactive power requirement and reactive power provision in the offshore grid 325

4.8.6 Flexible AC transmission systems (FACTS) 330

4.9 Integration of the Wind Energy into the Grid and Provision of Energy 333

4.9.1 Grid extension 333

4.9.2 Provision of energy 335

4.9.3 Control and reserve power 337

4.9.4 Power reserve provision with wind farms (Dissertation A. J. Gesino) 338

4.9.5 Intercontinental grid connections 346

References 346

5 Control and Supervision of Wind Turbines 355

5.1 System Requirements and Operating Modes 356

5.2 Isolated Operation of Wind Turbines 358

5.2.1 Turbines without a blade pitch adjustment mechanism 359

5.2.2 Plants with a blade pitch adjustment mechanism 360

5.2.3 Plants with load management 362

5.2.4 Turbine control by means of a bypass 362

5.3 Grid Operation of Wind Turbines 363

5.4 Control Concepts 367

5.4.1 Control in isolated operation 367

5.4.2 Regulation of variable-speed turbines 371

5.4.3 Regulation of variable-slip asynchronous generators 373

5.4.4 Regulation of turbines with a rigid connection to the grid 388

5.4.5 Wind turbine control using hydrodynamic variable-speed superimposing gears 390

5.5 Controller Design 390

5.5.1 Adjustment processes and torsional moments at the rotor blades 392

5.5.2 Standardizing and linearizing the variables 395

5.5.3 Control circuits and simplified dimensioning 400

5.5.4 Improving the control characteristics 404

5.5.5 Control design for wind turbines 410

5.6 Management System 411

5.6.1 Operating states 412

5.6.2 Faults 423

5.6.3 Determining the state of system components 424

5.7 Monitoring and Safety Systems 424

5.7.1 Wind measuring devices 425

5.7.2 Oscillation monitoring 425

5.7.3 Grid surveillance and lightning protection 426

5.7.4 Surveillance computer 426

5.7.5 Fault prediction 427

5.7.6 Voltage limitation 429

References 430

6 Using Wind Energy 436

6.1 Wind Conditions and Energy Yields 436

6.1.1 Global wind conditions 436

6.1.2 Local wind conditions and annual available power from the wind 438

6.1.3 Calculation of site-specific and regional turbine yields 440

6.1.4 Wind atlas methods 444

6.2 Potential and Expansion 449

6.2.1 Wind energy use on land 449

6.2.2 Offshore wind energy use 451

6.2.3 Repowering 453

6.3 Economic Considerations 455

6.3.1 Purchase and maintenance costs 457

6.3.2 Power supply and financial yields 457

6.3.3 Blue section 460

6.3.4 Commercial calculation methods 461

6.4 Legal Aspects and the Installation of Turbines 463

6.4.1 Immission protection 464

6.4.2 Nature and landscape conservation 467

6.4.3 Building laws 468

6.4.4 Planning and planning permission 469

6.4.5 Procedure for erecting a wind turbine 470

6.4.6 Offshore utilization of wind energy 472

6.5 Ecological Balance 474

6.5.1 Contribution to climate protection 474

6.5.2 Landscape utilization 475

6.5.3 Bird strike 475

6.5.4 Bats 475

6.5.5 Recycling of wind turbines 475

6.5.6 Energetic amortization time and harvest factor 476

References 476

Index 483