Preface xiii -- 1 Introduction to A Wind Energy Generation System 1 -- 1.1 Introduction 1 -- 1.2 Basic Concepts of a Fixed Speed Wind Turbine (FSWT) 2 -- 1.2.1 Basic Wind Turbine Description 2 -- 1.2.2 Power Control of Wind Turbines 5 -- 1.2.3 Wind Turbine Aerodynamics 7 -- 1.2.4 Example of a Commercial Wind Turbine 9 -- 1.3 Variable Speed Wind Turbines (VSWTs) 10 -- 1.3.1 Modeling of Variable Speed Wind Turbine 11 -- 1.3.2 Control of a Variable Speed Wind Turbine 15 -- 1.3.3 Electrical System of a Variable Speed Wind Turbine 22 -- 1.4 Wind Energy Generation System Based on DFIM VSWT 25 -- 1.4.1 Electrical Configuration of a VSWT Based on the DFIM 25 -- 1.4.2 Electrical Configuration of a Wind Farm 33 -- 1.4.3 WEGS Control Structure 34 -- 1.5 Grid Code Requirements 39 -- 1.5.1 Frequency and Voltage Operating Range 40 -- 1.5.2 Reactive Power and Voltage Control Capability 41 -- 1.5.3 Power Control 43 -- 1.5.4 Power System Stabilizer Function 45 -- 1.5.5 Low Voltage Ride Through (LVRT) 46 -- 1.6 Voltage Dips and LVRT 46 -- 1.6.1 Electric Power System 47 -- 1.6.2 Voltage Dips 50 -- 1.6.3 Spanish Verification Procedure 55 -- 1.7 VSWT Based on DFIM Manufacturers 57 -- 1.7.1 Industrial Solutions: Wind Turbine Manufacturers 57 -- 1.7.2 Modeling a 2.4 MW Wind Turbine 72 -- 1.7.3 Steady State Generator and Power Converter Sizing 79 -- 1.8 Introduction to the Next Chapters 83 -- Bibliography 85 -- 2 Back-to-Back Power Electronic Converter 87 -- 2.1 Introduction 87 -- 2.2 Back-to-Back Converter based on Two-Level VSC Topology 88 -- 2.2.1 Grid Side System 89 -- 2.2.2 Rotor Side Converter and dv/dt Filter 96 -- 2.2.3 DC Link 99 -- 2.2.4 Pulse Generation of the Controlled Switches 101 -- 2.3 Multilevel VSC Topologies 114 -- 2.3.1 Three-Level Neutral Point Clamped VSC Topology (3L-NPC) 116 -- 2.4 Control of Grid Side System 133 -- 2.4.1 Steady State Model of the Grid Side System 133 -- 2.4.2 Dynamic Modeling of the Grid Side System 139 -- 2.4.3 Vector Control of the Grid Side System 143.

2.5 Summary 152 -- References 153 -- 3 Steady State of the Doubly Fed Induction Machine 155 -- 3.1 Introduction 155 -- 3.2 Equivalent Electric Circuit at Steady State 156 -- 3.2.1 Basic Concepts on DFIM 156 -- 3.2.2 Steady State Equivalent Circuit 158 -- 3.2.3 Phasor Diagram 163 -- 3.3 Operation Modes Attending to Speed and Power Flows 165 -- 3.3.1 Basic Active Power Relations 165 -- 3.3.2 Torque Expressions 168 -- 3.3.3 Reactive Power Expressions 170 -- 3.3.4 Approximated Relations Between Active Powers, Torque, and Speeds 170 -- 3.3.5 Four Quadrant Modes of Operation 171 -- 3.4 Per Unit Transformation 173 -- 3.4.1 Base Values 175 -- 3.4.2 Per Unit Transformation of Magnitudes and Parameters 176 -- 3.4.3 Steady State Equations of the DFIM in p.u 177 -- 3.4.4 Example 3.1: Parameters of a 2 MW DFIM 179 -- 3.4.5 Example 3.2: Parameters of Different Power DFIM 180 -- 3.4.6 Example 3.3: Phasor Diagram of a 2 MW DFIM and p.u. Analysis 181 -- 3.5 Steady State Curves: Performance Evaluation 184 -- 3.5.1 Rotor Voltage Variation: Frequency, Amplitude, and Phase Shift 185 -- 3.5.2 Rotor Voltage Variation: Constant Voltage-Frequency (V-F) Ratio 192 -- 3.5.3 Rotor Voltage Variation: Control of Stator Reactive Power and Torque 195 -- 3.6 Design Requirements for the DFIM in Wind Energy Generation Applications 202 -- 3.7 Summary 207 -- References 208 -- 4 Dynamic Modeling of the Doubly Fed Induction Machine 209 -- 4.1 Introduction 209 -- 4.2 Dynamic Modeling of the DFIM 210 -- 4.2.1 ab Model 212 -- 4.2.2 dq Model 214 -- 4.2.3 State-Space Representation of ab Model 216 -- 4.2.4 State-Space Representation of dq Model 229 -- 4.2.5 Relation Between the Steady State Model and the Dynamic Model 234 -- 4.3 Summary 238 -- References 238 -- 5 Testing the DFIM 241 -- 5.1 Introduction 241 -- 5.2 Off-Line Estimation of DFIM Model Parameters 242 -- 5.2.1 Considerations About the Model Parameters of the DFIM 243 -- 5.2.2 Stator and Rotor Resistances Estimation by VSC 245 -- 5.2.3 Leakage Inductances Estimation by VSC 250.

5.2.4 Magnetizing Inductance and Iron Losses Estimation with No-Load Test by VSC 256 -- 5.3 Summary 262 -- References 262 -- 6 Analysis of the DFIM Under Voltage Dips 265 -- 6.1 Introduction 265 -- 6.2 Electromagnetic Force Induced in the Rotor 266 -- 6.3 Normal Operation 267 -- 6.4 Three-Phase Voltage Dips 268 -- 6.4.1 Total Voltage Dip, Rotor Open-Circuited 268 -- 6.4.2 Partial Voltage Dip, Rotor Open-Circuited 273 -- 6.5 Asymmetrical Voltage Dips 278 -- 6.5.1 Fundamentals of the Symmetrical Component Method 278 -- 6.5.2 Symmetrical Components Applied to the DFIM 281 -- 6.5.3 Single-Phase Dip 283 -- 6.5.4 Phase-to-Phase Dip 286 -- 6.6 Influence of the Rotor Currents 290 -- 6.6.1 Influence of the Rotor Current in a Total Three-Phase Voltage Dip 291 -- 6.6.2 Rotor Voltage in a General Case 294 -- 6.7 DFIM Equivalent Model During Voltage Dips 297 -- 6.7.1 Equivalent Model in Case of Linearity 297 -- 6.7.2 Equivalent Model in Case of Nonlinearity 299 -- 6.7.3 Model of the Grid 300 -- 6.8 Summary 300 -- References 301 -- 7 Vector Control Strategies for Grid-Connected DFIM Wind Turbines 303 -- 7.1 Introduction 303 -- 7.2 Vector Control 304 -- 7.2.1 Calculation of the Current References 305 -- 7.2.2 Limitation of the Current References 307 -- 7.2.3 Current Control Loops 308 -- 7.2.4 Reference Frame Orientations 311 -- 7.2.5 Complete Control System 313 -- 7.3 Small Signal Stability of the Vector Control 314 -- 7.3.1 Influence of the Reference Frame Orientation 314 -- 7.3.2 Influence of the Tuning of the Regulators 320 -- 7.4 Vector Control Behavior Under Unbalanced Conditions 327 -- 7.4.1 Reference Frame Orientation 328 -- 7.4.2 Saturation of the Rotor Converter 328 -- 7.4.3 Oscillations in the Stator Current and in the Electromagnetic Torque 328 -- 7.5 Vector Control Behavior Under Voltage Dips 331 -- 7.5.1 Small Dips 333 -- 7.5.2 Severe Dips 336 -- 7.6 Control Solutions for Grid Disturbances 340 -- 7.6.1 Demagnetizing Current 340 -- 7.6.2 Dual Control Techniques 346 -- 7.7 Summary 358.

References 360 -- 8 Direct Control of the Doubly Fed Induction Machine 363 -- 8.1 Introduction 363 -- 8.2 Direct Torque Control (DTC) of the Doubly Fed Induction Machine 364 -- 8.2.1 Basic Control Principle 365 -- 8.2.2 Control Block Diagram 371 -- 8.2.3 Example 8.1: Direct Torque Control of a 2 MW DFIM 377 -- 8.2.4 Study of Rotor Voltage Vector Effect in the DFIM 379 -- 8.2.5 Example 8.2: Spectrum Analysis in Direct Torque Control of a 2 MW DFIM 384 -- 8.2.6 Rotor Flux Amplitude Reference Generation 386 -- 8.3 Direct Power Control (DPC) of the Doubly Fed Induction Machine 387 -- 8.3.1 Basic Control Principle 387 -- 8.3.2 Control Block Diagram 390 -- 8.3.3 Example 8.3: Direct Power Control of a 2 MW DFIM 395 -- 8.3.4 Study of Rotor Voltage Vector Effect in the DFIM 395 -- 8.4 Predictive Direct Torque Control (P-DTC) of the Doubly Fed Induction Machine at Constant Switching Frequency 399 -- 8.4.1 Basic Control Principle 399 -- 8.4.2 Control Block Diagram 402 -- 8.4.3 Example 8.4: Predictive Direct Torque Control of 15kW and 2 MW DFIMs at 800 Hz Constant -- Switching Frequency 411 -- 8.4.4 Example 8.5: Predictive Direct Torque Control of a 15kW DFIM at 4 kHz Constant Switching Frequency 415 -- 8.5 Predictive Direct Power Control (P-DPC) of the Doubly Fed Induction Machine at Constant Switching Frequency 416 -- 8.5.1 Basic Control Principle 417 -- 8.5.2 Control Block Diagram 419 -- 8.5.3 Example 8.6: Predictive Direct Power Control of a 15 kW DFIM at 1 kHz Constant Switching Frequency 424 -- 8.6 Multilevel Converter Based Predictive Direct Power and Direct Torque Control of the Doubly Fed Induction Machine at Constant Switching Frequency 425 -- 8.6.1 Introduction 425 -- 8.6.2 Three-Level NPC VSC Based DPC of the DFIM 428 -- 8.6.3 Three-Level NPC VSC Based DTC of the DFIM 447 -- 8.7 Control Solutions for Grid Voltage Disturbances, Based on Direct Control Techniques 451 -- 8.7.1 Introduction 451 -- 8.7.2 Control for Unbalanced Voltage Based on DPC 452 -- 8.7.3 Control for Unbalanced Voltage Based on DTC 460.

8.7.4 Control for Voltage Dips Based on DTC 467 -- 8.8 Summary 473 -- References 474 -- 9 Hardware Solutions for LVRT 479 -- 9.1 Introduction 479 -- 9.2 Grid Codes Related to LVRT 479 -- 9.3 Crowbar 481 -- 9.3.1 Design of an Active Crowbar 484 -- 9.3.2 Behavior Under Three-Phase Dips 486 -- 9.3.3 Behavior Under Asymmetrical Dips 488 -- 9.3.4 Combination of Crowbar and Software Solutions 490 -- 9.4 Braking Chopper 492 -- 9.4.1 Performance of a Braking Chopper Installed Alone 492 -- 9.4.2 Combination of Crowbar and Braking Chopper 493 -- 9.5 Other Protection Techniques 495 -- 9.5.1 Replacement Loads 495 -- 9.5.2 Wind Farm Solutions 496 -- 9.6 Summary 497 -- References 498 -- 10 Complementary Control Issues: Estimator Structures and Start-Up of Grid-Connected DFIM 501 -- 10.1 Introduction 501 -- 10.2 Estimator and Observer Structures 502 -- 10.2.1 General Considerations 502 -- 10.2.2 Stator Active and Reactive Power Estimation for Rotor Side DPC 503 -- 10.2.3 Stator Flux Estimator from Stator Voltage for Rotor Side Vector Control 503 -- 10.2.4 Stator Flux Synchronization from Stator Voltage for Rotor Side Vector Control 506 -- 10.2.5 Stator and Rotor Fluxes Estimation for Rotor Side DPC, DTC, and Vector Control 507 -- 10.2.6 Stator and Rotor Flux Full Order Observer 508 -- 10.3 Start-up of the Doubly Fed Induction Machine Based Wind Turbine 512 -- 10.3.1 Encoder Calibration 514 -- 10.3.2 Synchronization with the Grid 518 -- 10.3.3 Sequential Start-up of the DFIM Based Wind Turbine 523 -- 10.4 Summary 534 -- References 535 -- 11 Stand-Alone DFIM Based Generation Systems 537 -- 11.1 Introduction 537 -- 11.1.1 Requirements of Stand-alone DFIM Based System 537 -- 11.1.2 Characteristics of DFIM Supported by DC Coupled Storage 540 -- 11.1.3 Selection of Filtering Capacitors 541 -- 11.2 Mathematical Description of the Stand-Alone DFIM System 544 -- 11.2.1 Model of Stand-alone DFIM 544 -- 11.2.2 Model of Stand-alone DFIM Fed from Current Source 549 -- 11.2.3 Polar Frame Model of Stand-alone DFIM 551.

11.2.4 Polar Frame Model of Stand-alone DFIM Fed from Current Source 554 -- 11.3 Stator Voltage Control 558 -- 11.3.1 Amplitude and Frequency Control by the Use of PLL 558 -- 11.3.2 Voltage Asymmetry Correction During Unbalanced Load Supply 567 -- 11.3.3 Voltage Harmonics Reduction During Nonlinear Load Supply 569 -- 11.4 Synchronization Before Grid Connection By Superior PLL 573 -- 11.5 Summary 576 -- References 577 -- 12 New Trends on Wind Energy Generation 579 -- 12.1 Introduction 579 -- 12.2 Future Challenges for Wind Energy Generation: What must be Innovated 580 -- 12.2.1 Wind Farm Location 580 -- 12.2.2 Power, Efficiency, and Reliability Increase 582 -- 12.2.3 Electric Grid Integration 583 -- 12.2.4 Environmental Concerns 583 -- 12.3 Technological Trends: How They Can be Achieved 584 -- 12.3.1 Mechanical Structure of the Wind Turbine 585 -- 12.3.2 Power Train Technology 586 -- 12.4 Summary 599 -- References 600 -- Appendix 603 -- A.1 Space Vector Representation 603 -- A.1.1 Space Vector Notation 603 -- A.1.2 Transformations to Different Reference Frames 606 -- A.1.3 Power Expressions 609 -- A.2 Dynamic Modeling of the DFIM Considering the Iron Losses 610 -- A.2.1 ab Model 611 -- A.2.2 dq Model 614 -- A.2.3 State-Space Representation of ab Model 616 -- References 618 -- Index 619 -- The IEEE Press Series on Power Engineering.