## Contents

Preface to the Second Edition…………………………………………………………………….. xiii

Preface to the First Edition………………………………………………………………………….. xv

Author………………………………………………………………………………………………………. xix

1 Wound-Rotor Induction Generators: Steady State

1.1 Introduction……………………………………………………………………………………………………………………….1

1.2 Construction Elements……………………………………………………………………………………………………… 3

1.2.1 Magnetic Cores ½ 4

1.2.2 Windings and Their Magnetomotive Forces……………………………………………………….. 5

1.2.3 Slip-Rings and Brushes………………………………………………………………………………………… 8

1.3 Steady-State Equations………………………………………………………………………………………………………. 9

1.4 Equivalent Circuit……………………………………………………………………………………………………………. 11

1.5 Phasor Diagrams………………………………………………………………………………………………………………13

1.6 Operation at the Power Grid……………………………………………………………………………………………..18

1.6.1 Stator Power versus Power Angle…………………………………………………………………………19

1.6.2 Rotor Power versus Power Angle…………………………………………………………………………21

1.6.3 Operation at Zero Slip (S = 0)………………………………………………………………………………21

1.7 Autonomous Operation of WRIGs………………………………………………………………………………….. 22

1.8 Operation of WRIGs in the Brushless Exciter Mode……………………………………………………….. 26

1.9 Losses and Efficiency of WRIGs………………………………………………………………………………………..31

1.10 Summary…………………………………………………………………………………………………………………………. 32

References

2 Wound-Rotor Induction Generators: Transients and Control

2.1 Introduction……………………………………………………………………………………………………………………. 37

2.2 WRIG Phase Coordinate Model……………………………………………………………………………………… 37

2.3 Space-Phasor Model of WRIG………………………………………………………………………………………….40

2.4 Space-Phasor Equivalent Circuits and Diagrams…………………………………………………………….. 42

2.5 Approaches to WRIG Transients……………………………………………………………………………………..46

2.6 Static Power Converters for WRIGs………………………………………………………………………………… 47

2.6.1 Direct AC–AC Converters…………………………………………………………………………………. 50

2.6.2 DC Voltage Link AC–AC Converters…………………………………………………………………. 52

2.7 Vector Control of WRIG at Power Grid…………………………………………………………………………… 54

2.7.1 Principles of Vector Control of Machine (Rotor)-Side Converter………………………. 54

2.7.2 Vector Control of Source-Side Converter…………………………………………………………… 57

vi Contents

2.7.3 Wind Power WRIG Vector Control at the Power Grid………………………………………. 59

2.7.3.1 Wind Turbine Model…………………………………………………………………………. 59

2.7.3.2 Supply-Side Converter Model………………………………………………………………61

2.7.3.3 Generator-Side Converter Model……………………………………………………….. 62

2.7.3.4 Simulation Results……………………………………………………………………………… 63

2.7.3.5 Three-Phase Short Circuit on the Power Grid……………………………………. 65

2.7.3.6 Mechanism to Improve Performance during Fault……………………………. 67

2.8 Direct Power Control of WRIG at Power Grid………………………………………………………………… 68

2.8.1 Concept of DPC

2.9 Independent Vector Control of Positive and Negative Sequence Currents………………………. 74

2.10 Motion-Sensorless Control……………………………………………………………………………………………… 76

2.11 Vector Control in Stand-Alone Operation………………………………………………………………………. 79

2.12 Self-Starting, Synchronization, and Loading at the Power Grid……………………………………… 80

2.13 Voltage and Current Low-Frequency Harmonics of WRIG…………………………………………….. 83

2.14 Ride-Through Control of DFIG under Unbalanced Voltage Sags……………………………………. 86

2.15 Stand-Alone DFIG Control under Unbalanced Nonlinear Loads……………………………………. 89

2.16 Summary…………………………………………………………………………………………………………………………..91

References

3 Wound-Rotor Induction Generators: Design and Testing

3.1 Introduction……………………………………………………………………………………………………………………. 95

3.2 Design Specifications: An Example………………………………………………………………………………….96

3.3 Stator Design……………………………………………………………………………………………………………………96

3.4 Rotor Design……………………………………………………………………………………………………………………103

3.5 Magnetization Current……………………………………………………………………………………………………106

3.6 Reactances and Resistances…………………………………………………………………………………………….109

3.7 Electrical Losses and Efficiency………………………………………………………………………………………. 113

3.8 Testing of WRIGs…………………………………………………………………………………………………………… 115

3.9 Summary………………………………………………………………………………………………………………………… 116

References

4 Self-Excited Induction Generators

4.1 Introduction…………………………………………………………………………………………………………………… 119

4.2 Principle of Cage-Rotor Induction Machine…………………………………………………………………… 119

4.3 Self-Excitation: A Qualitative View…………………………………………………………………………………122

4.4 Steady-State Performance of Three-Phase SEIGs…………………………………………………………….123

4.4.1 Second-Order Slip Equation Methods……………………………………………………………….124

4.4.2 SEIGs with Series Capacitance Compensation…………………………………………………..128

4.5 Performance Sensitivity Analysis……………………………………………………………………………………128

4.5.1 For Constant Speed……………………………………………………………………………………………129

4.5.2 For Unregulated Prime Movers…………………………………………………………………………130

4.6 Pole Changing SEIGs for Variable Speed Operation………………………………………………………. 131

4.7 Unbalanced Operation of Three-Phase SEIGs…………………………………………………………………133

4.8 One Phase Open at Power Grid……………………………………………………………………………………….136

4.9 Three-Phase SEIG with Single-Phase Output………………………………………………………………….138

4.10 Two-Phase SEIGs with Single-Phase Output…………………………………………………………………..142

4.11 Three-Phase SEIG Transients………………………………………………………………………………………….145

4.12 Parallel Connection of SEIGs………………………………………………………………………………………….148

4.13 Direct Connection to Grid Transients in Cage-Rotor Induction Generators…………………..150

Contents vii

4.14 More on Power Grid Disturbance Transients in Cage-Rotor Induction

Generators

4.15 Summary…………………………………………………………………………………………………………………………160

References

5 Stator-Converter-Controlled Induction Generators

5.1 Introduction……………………………………………………………………………………………………………………165

5.2 Grid-Connected SCIGs: The Control System………………………………………………………………….166

5.2.1 Machine-Side PWM Converter Control…………………………………………………………….166

5.2.1.1 State Observers for DTFC of SCIGs…………………………………………………..167

5.2.1.2 DTFC–SVM Block…………………………………………………………………………….173

5.2.2 Grid-Side Converter Control……………………………………………………………………………..176

5.3 Grid Connection and Four-Quadrant Operation of SCIGs…………………………………………….176

5.4 Stand-Alone Operation of SCIG………………………………………………………………………………………179

5.5 Parallel Operation of SCIGs…………………………………………………………………………………………….180

5.6 Static Capacitor Exciter Stand-Alone IG for Pumping Systems………………………………………. 181

5.7 Operation of SCIGs with DC Voltage-Controlled Output………………………………………………184

5.8 Stand-Alone SCIG with AC Output and Low Rating PWM Converter…………………………..187

5.9 Dual Stator Winding for Grid Applications…………………………………………………………………….187

5.10 Twin Stator Winding SCIG with 50% Rating Inverter and Diode Rectifier…………………….189

5.11 Dual Stator Winding IG with Nested Cage Rotor……………………………………………………………190

5.12 Summary…………………………………………………………………………………………………………………………190

References

6 Automotive Claw-Pole-Rotor Generator Systems

6.1 Introduction……………………………………………………………………………………………………………………195

6.2 Construction and Principle…………………………………………………………………………………………….195

6.3 Magnetic Equivalent Circuit Modeling………………………………………………………………………….200

6.4 Three-Dimensional Finite Element Method Modeling………………………………………………….. 203

6.5 Losses, Efficiency, and Power Factor……………………………………………………………………………… 208

6.6 Design Improvement Steps……………………………………………………………………………………………..210

6.6.1 Claw-Pole Geometry………………………………………………………………………………………….210

6.6.2 Booster Diode Effects………………………………………………………………………………………… 211

6.6.3 Assisting Permanent Magnets……………………………………………………………………………212

6.6.4 Increasing the Number of Poles…………………………………………………………………………213

6.6.5 Winding Tapping (Reconfiguration)…………………………………………………………………213

6.6.6 Claw-Pole Damper…………………………………………………………………………………………….216

6.6.7 Controlled Rectifier……………………………………………………………………………………………216

6.7 Lundell Starter/Generator for Hybrid Vehicles……………………………………………………………….217

6.8 IPM Claw-Pole Alternator System for More Vehicle Braking Energy Recuperation:

A Case Study 6.8.1 3D Nonlinear Magnetic Circuit Model…………………………………………………………….. 225

6.8.1.1 Evaluation Design Calibration…………………………………………………………. 226

6.8.2 Optimal Design: Method, Code, and Sample Results with Prototype

Test Results 6.8.3 3D-FEM Analysis…………………………………………………………………………………………….. 229

6.8.4 Vehicle Braking Energy Recuperation Scheme and Its Control……………………….. 232

6.8.4.1 Dynamic Model of the Proposed System…………………………………………. 233

6.8.4.2 42 VDC Storage Battery Model…………………………………………………………… 236

viii Contents

6.8.4.3 Control Strategy……………………………………………………………………………….. 237

6.8.4.4 Simulation Results……………………………………………………………………………. 238

6.8.5 Extension of IPM Alternator Utilization up to 100 kW Systems………………………..241

6.9 Summary…………………………………………………………………………………………………………………………241

References

7 Induction Starter/Alternators for Electric Hybrid Vehicles

7.1 Electric Hybrid Vehicle Configuration………………………………………………………………………….. 245

7.2 Essential Specifications………………………………………………………………………………………………….. 248

7.2.1 Peak Torque (Motoring) and Power (Generating)……………………………………………. 248

7.2.2 Battery Parameters and Characteristics…………………………………………………………… 250

7.3 Topology Aspects of Induction Starter/Alternator…………………………………………………………. 253

7.4 ISA Space-Phasor Model and Characteristics………………………………………………………………… 255

7.5 Vector Control of ISA…………………………………………………………………………………………………….. 263

7.6 DTFC of ISA…………………………………………………………………………………………………………………..264

7.7 ISA Design Issues for Variable Speed……………………………………………………………………………..266

7.7.1 Power and Voltage Derating……………………………………………………………………………..266

7.7.2 Increasing Efficiency………………………………………………………………………………………… 267

7.7.3 Increasing the Breakdown Torque…………………………………………………………………….268

7.7.4 Additional Measures for Wide Constant Power Range……………………………………. 269

7.7.4.1 Winding Reconfiguration………………………………………………………………… 270

7.8 Summary……………………………………………………………………………………………………………………….. 273

8 Permanent-Magnet-Assisted Reluctance Synchronous Starter/

Alternators for Electric Hybrid Vehicles

8.1 Introduction………………………………………………………………………………………………………………….. 279

8.2 Topologies of PM-RSM…………………………………………………………………………………………………..280

8.3 Finite Element Analysis…………………………………………………………………………………………………. 283

8.3.1 Flux Distribution……………………………………………………………………………………………… 283

8.3.2 dq Inductances

8.3.3 Cogging Torque

8.3.4 Core Losses Computation by FEM…………………………………………………………………… 289

8.4 dq Model of PM-RSM……………………………………………………………………………………………………..291

8.5 Steady-State Operation at No Load and Symmetric Short Circuit…………………………………. 297

8.5.1 Generator No-Load………………………………………………………………………………………….. 297

8.5.2 Symmetrical Short Circuit……………………………………………………………………………….. 297

8.6 Design Aspects for Wide Speed Range Constant Power Operation………………………………..299

8.7 Power Electronics for PM-RSM for Automotive Applications……………………………………….. 305

8.8 Control of PM-RSM for EHV………………………………………………………………………………………… 307

8.9 State Observers without Signal Injection for Motion Sensorless Control………………………..310

8.10 Signal Injection Rotor Position Observers………………………………………………………………………312

8.11 Initial and Low-Speed Rotor Position Tracking………………………………………………………………313

8.12 50/100 kW, 1350–7000 rpm (600 Nm Peak Torque, 40 kg) PM-Assisted Reluctance

Synchronous Motor/Generator for HEV: A Case Study

8.12.2 General Design Summary and Results………………………………………………………………318

8.12.2.1 Stator Core Geometry………………………………………………………………………..318

8.12.2.2 Number of Turns per Coil nc……………………………………………………………..319

8.12.2.3 The Stator Leakage Inductance Ls1 and Ldm/Lqm Requirements…………..319

Contents ix

8.12.2.4 Rotor Lamination Design………………………………………………………………… 320

8.12.2.5 Peak Torque Production…………………………………………………………………… 320

8.12.2.6 Slot Area/Peak Current Density/Stator Resistance Rs………………………..321

8.12.2.7 Weights of Active Materials……………………………………………………………….321

8.12.2.8 Performance at 100 kW and 7000 rpm……………………………………………… 322

8.12.2.9 Performance at 50 kW, 7000 rpm, and 1350 rpm……………………………… 323

8.12.2.10 Equivalent Circuit……………………………………………………………………………. 323

8.12.3 Optimal Design Methodology and Results………………………………………………………. 324

8.12.3.1 IPMSM—Analytical Model……………………………………………………………… 324

8.12.3.2 Optimal Design of IPMSM………………………………………………………………. 324

8.12.4 FEM Validation without and with Rotor Segmentation…………………………………… 327

8.12.5 Dynamic Model and Vector Control Performance Validation…………………………. 330

8.13 Summary…………………………………………………………………………………………………………………………333

9 Switched Reluctance Generators and Their Control

9.1 Introduction………………………………………………………………………………………………………………….. 339

9.2 Practical Topologies and Principles of Operation………………………………………………………….. 339

9.2.1 kW/Peak kVA Ratio…………………………………………………………………………………………..344

9.3 SRG(M) Modeling………………………………………………………………………………………………………….346

9.4 Flux/Current/Position Curves………………………………………………………………………………………..348

9.5 Design Issues…………………………………………………………………………………………………………………. 349

9.5.1 Motor and Generator Specifications………………………………………………………………… 350

9.5.2 Number of Phases, Stator and Rotor Poles: m, Ns, Nr…………………………………………351

9.5.3 Stator Bore Diameter Dis and Stack Length……………………………………………………….351

9.5.4 Number of Turns per Coil Wc for Motoring…………………………………………………….. 353

9.5.5 Current Waveforms for Generator Mode…………………………………………………………. 353

9.6 PWM Converters for SRGs……………………………………………………………………………………………. 356

9.7 Control of SRG(M)s……………………………………………………………………………………………………….. 358

9.7.1 Feed-Forward Torque Control of SRG(M) with Position Feedback………………….. 359

9.8 Direct Torque Control of SRG(M)………………………………………………………………………………….364

9.9 Rotor Position and Speed Observers for Motion-Sensorless Control……………………………..366

9.9.1 Signal Injection for Standstill Position Estimation……………………………………………366

9.10 Output Voltage Control in SRG……………………………………………………………………………………… 369

9.11 Double Stator SRG with Segmented Rotor…………………………………………………………………….. 370

9.12 Summary…………………………………………………………………………………………………………………………371

10 Permanent Magnet Synchronous Generator Systems

10.1 Introduction………………………………………………………………………………………………………………….. 377

10.2 Practical Configurations and Their Characterization……………………………………………………. 378

10.2.1 Distributed versus Concentrated Windings…………………………………………………….. 383

10.3 Air Gap Field Distribution, emf, and Torque…………………………………………………………………. 386

10.4 Stator Core Loss Modeling…………………………………………………………………………………………….. 394

10.4.1 FEM-Derived Core Loss Formulas…………………………………………………………………… 394

10.4.2 Simplified Analytical Core Loss Formulas……………………………………………………….. 398

10.5 Circuit Model………………………………………………………………………………………………………………….401

10.5.1 Phase Coordinate Model……………………………………………………………………………………401

10.5.2 dq Model of PMSG……………………………………………………………………………………………402

10.6 Circuit Model of PMSG with Shunt Capacitors and AC Load………………………………………..408

x Contents

10.7 Circuit Model of PMSG with Diode Rectifier Load…………………………………………………………410

10.8 Utilization of Third Harmonic for PMSG with Diode Rectifiers…………………………………….. 411

10.9 Autonomous PMSGs with Controlled Constant Speed and AC Load……………………………..415

10.10 Grid-Connected Variable-Speed PMSG System………………………………………………………………418

10.10.1 Diode Rectifier and Boost DC–DC Converter Case………………………………………….420

10.11 PM Genset with Multiple Outputs………………………………………………………………………………….422

10.12 Super-High-Speed PM Generators: Design Issues………………………………………………………….426

10.14 Design of a 42 VDC Battery-Controlled-Output PMSG System……………………………………….434

10.14.1 Design Initial Data…………………………………………………………………………………………… 435

10.14.2 Minimum Speed: nmin………………………………………………………………………………………. 435

10.14.3 Number of Poles: 2p1………………………………………………………………………………………… 437

10.14.4 Rotor Configuration………………………………………………………………………………………… 437

10.14.5 Stator Winding Type………………………………………………………………………………………… 438

10.14.6 Winding Tapping…………………………………………………………………………………………….. 439

10.14.7 PMSG Current Waveform…………………………………………………………………………………440

10.14.8 Diode Rectifier Imposes Almost Unity Power Factor……………………………………….440

10.14.9 Peak Torque-Based Sizing…………………………………………………………………………………440

10.14.10 Generator-to-DC Voltage Relationships……………………………………………………………440

10.14.11 ΨPM, Ls, and Rs

10.15.2 No-Load Generator Tests………………………………………………………………………………….447

10.15.3 Short-Circuit Generator Tests…………………………………………………………………………..448

10.15.4 Stator Leakage Inductance and Skin Effect……………………………………………………….448

10.15.5 Motor No-Load Test………………………………………………………………………………………….450

10.15.6 Generator Load Tests………………………………………………………………………………………..450

10.16 Grid to Stand-Alone Transition Motion-Sensorless Dual-Inverter Control

of PMSG with Asymmetrical Grid Voltage Sags and Harmonics Filtering:

A Case Study

10.16.1.2 Line Voltage Angle Estimation………………………………………………………… 457

10.16.2 Stand-Alone PMSG Control: Harmonic and Negative-Sequence Voltage

Compensation under Nonlinear Load

10.16.3 Seamless Switching Transfer from Stand-Alone to Grid (and Back)………………… 458

10.16.3.1 Transition from Stand-Alone to Grid-Connected Mode………………….. 459

10.16.3.2 Transition from Grid-Connected to Stand-Alone Mode…………………..460

10.16.4 PMSG Motion-Sensorless Control System………………………………………………………..460

10.16.4.1 PMSG Modeling……………………………………………………………………………….460

10.16.4.2 Active Power and Current Control…………………………………………………….461

10.16.4.3 Rotor Position and Speed Observer…………………………………………………..463

10.16.5 Test Platform and Experimental Results…………………………………………………………..464

10.16.5.1 Voltage Sags Ride-Through……………………………………………………………….464

10.16.5.2 Harmonic and Negative-Sequence Voltage Compensation

Contents xi

10.16.5.3 Transition from Stand-Alone to Grid-Connected Mode…………………..467

10.16.5.4 Transition from Grid-Connected to Stand-Alone Mode…………………..469

10.16.6 Conclusion 10.17 Note on Medium-Power Vehicular Electric Generator Systems………………………………………471

10.18 Summary……………………………………………………………………………………………………………………….. 472

11 Transverse Flux and Flux Reversal Permanent Magnet Generator Systems

11.1 Introduction………………………………………………………………………………………………………………….. 479

11.2 Three-Phase Transverse Flux Machine: Magnetic Circuit Design………………………………….485

11.2.1 Phase Inductance Ls………………………………………………………………………………………….489

11.2.2 Phase Resistance and Slot Area…………………………………………………………………………490

11.3 TFM: The dq Model and Steady State…………………………………………………………………………….. 493

11.4 Three-Phase FR-PM Generator: Magnetic and Electric Circuit Design

11.4.1 Preliminary Geometry for 200 Nm at 128 rpm via Conceptual Design…………….499

11.4.2 FEM Analysis of Pole-PM FRM at No Load……………………………………………………..500

11.4.3 FEM Analysis at Steady State on Load……………………………………………………………… 502

11.4.4 FEM Computation of Inductances…………………………………………………………………… 508

11.4.5 Inductances and the Circuit Model of FRM…………………………………………………….. 508

11.4.6 dq Model of FRM……………………………………………………………………………………………….510

11.4.7 Notes on Flux Reversal Generator Control………………………………………………………..517

11.5 High Power Factor Vernier PM Generators…………………………………………………………………….521

11.5.1 Power Factor of VPM Machine………………………………………………………………………….521

11.5.1.1 Power Factor………………………………………………………………………………………521

11.5.2 DSSA: VPM for Higher Power Factor………………………………………………………………. 523

11.6 Summary……………………………………………………………………………………………………………………….. 525

12 Linear Motion Alternators

12.1 Introduction………………………………………………………………………………………………………………….. 529

12.2 LMA Principle of Operation………………………………………………………………………………………….. 529

12.2.1 Motion Equation……………………………………………………………………………………………… 532

12.3 PM-LMA with Coil Mover………………………………………………………………………………………………533

12.4 Multipole LMA with Coil Plus Iron Mover……………………………………………………………………. 535

12.5 PM-Mover LMAs…………………………………………………………………………………………………………….541

12.6 Tubular Homopolar PM Mover Single-Coil LMA………………………………………………………….544

12.7 Flux Reversal LMA with Mover PM Flux Concentration………………………………………………. 549

12.8 PM-LMAs with Iron Mover…………………………………………………………………………………………… 555

12.9 Flux Reversal PM-LMA Tubular Configuration……………………………………………………………. 555

12.9.1 The Analytical Model………………………………………………………………………………………. 555

12.10 Control of PM-LMAs……………………………………………………………………………………………………..560

12.10.1 Electrical Control……………………………………………………………………………………………..560

12.10.2 Spark-Ignited Gasoline Linear Engine Model………………………………………………….. 562

12.10.3 Note on Stirling Engine LMA Stability…………………………………………………………….. 562

12.11 Progressive-Motion LMAs for Maglevs with Active Guideway……………………………………… 563

12.11.1 Note on Magnetohydrodynamic Linear Generators…………………………………………566

12.12 Summary………………………………………………………………………………………………………………………..566

References

Index……………………………………………………………………………………………………….. 569

## Preface to the Second Edition

The first edition of this single-author, two-book set was published in 2006. Since then, electric energy,

“produced” mostly via electric generators, has become one of the foremost activities in our global economy

world. The subject of electric generators (Synchronous Generators and Variable Speed Generators as

two books) attracted special attention worldwide both from industry and academia in the last decade.

Electric generators’ design and control may constitute a new graduate course in universities with electric

power programs.

Also, in the design and control of electric generators for applications ranging from energy conversion

to electric vehicles (transportation) and auxiliary power sources, new knowledge and developments

have been published in the last ten years. In the last ten years, in wind generators alone, the installed

power has increased from some 40,000 MW to 300,000 MW (in 2014).

In view of these developments, we decided to come up with a new edition that

• Keeps the structure of the first edition to avoid confusion for users

• Keeps the style with many numerical worked-out examples of practical interest, together with

more complete case studies

• Includes text and number corrections

• Adds quite a few new paragraphs in both books, totaling around 100 pages, to illustrate synthetically

the progress in the field in the last decade

The new additions in the second edition are

Synchronous Generators

• Chapter 2 (Section 2.9): High Power Wind Generators, with less or no PM—an overview

• Chapter 4 (Section 4.15): PM-Assisted DC-Excited Salient Pole Synchronous Generators

(Section 4.16): Multiphase Synchronous Machine Inductances via Winding Function

Method

• Chapter 6 (Section 6.17): Note on Autonomous Synchronous Generators’ Control

• Chapter 7 (Section 7.21): Optimization Design Issues

(Section 7.21.1): Optimal Design of a Large Wind Generator by Hooke–Jeeves Method

(Section 7.21.2): Magnetic Equivalent Circuit Population-Based Optimal Design of

Synchronous Generators

• Chapter 8 (Section 8.10): Online Identification of SG Parameters

(Section 8.10.1): Small-Signal Injection online Technique

(Section 8.10.2): Line Switching (On or Off) Parameter Identification for Isolated Grids

(Section 8.10.3): Synthetic Back-to-Back Load Testing with Inverter Supply

xiv Preface to the Second Edition

Variable Speed Generators

• Chapter 2 (Section 2.14): Ride-Through Control of DFIG under Unbalanced Voltage Sags

(Section 2.15): Stand-Alone DFIG Control under Unbalanced Nonlinear Loads

• Chapter 5 (Section 5.8): Stand-Alone SCIG with AC Output and Low Rating PWM Converter

(Section 5.10): Twin Stator Winding SCIG with 50% Rating Inverter and Diode Rectifier

(Section 5.11): Dual Stator Winding IG with Nested Cage Rotor

• Chapter 6 (Section 6.8): IPM Claw-Pole Alternator System for More Vehicle Braking Energy

Recuperation: A Case Study

• Chapter 8 (Section 8.12): 50/100 kW, 1350–7000 rpm (600 N m Peak Torque, 40 kg) PM-Assisted

Reluctance Synchronous Motor/Generator for HEV: A Case Study

• Chapter 9 (Section 9.11): Double Stator SRG with Segmented Rotor

• Chapter 10 (Section 10.16): Grid to Stand-Alone Transition Motion-Sensorless Dual-Inverter

Control of PMSG with Asymmetrical Grid Voltage Sags and Harmonics

Filtering: A Case Study

• Chapter 11 (Section 11.5): High Power Factor Vernier PM Generators

We hope that the second edition will be of good use to graduate students, to faculty, and, especially,

to R&D engineers in industry that deal with electric generators, design control, fabrication, testing,

commissioning, and maintenance. We look forward to the readers’ comments for their confirmation

and validation and for further improvement of the second edition of these two books: Synchronous

Generators and Variable Speed Generators.

## Preface to the First Edition

Electric energy is a key factor for civilization. Natural (fossil) fuels such as coal, natural gas, and nuclear

fuel are fired to produce heat in a combustor and then the thermal energy is converted into mechanical

energy in a turbine (prime mover). The turbine drives an electric generator to produce electric energy.

Water potential and kinetic and wind energy are also converted to mechanical energy in prime movers

(turbine) to drive an electric generator.

All primary energy resources are limited, and they have a thermal and chemical (pollutant) effect on

the environment.

Currently, much of electric energy is produced in constant-speed-regulated synchronous generators

that deliver electric energy with constant AC voltage and frequency into regional and national electric

power systems, which further transport and distribute it to consumers.

In an effort to reduce environment effects, electric energy markets have been recently made more

open, and more flexible distributed electric power systems have emerged. The introduction of distributed

power systems is leading to an increased diversity and growth of a wider range power/unit electric

energy suppliers. Stability, quick and efficient delivery, and control of electric power in such distributed

systems require some degree of power electronics control to allow lower speed for lower power in electric

generators to tap the primary fuel energy.

This is how variable-speed electric generators have come into play recently [up to 400 (300) MVA/

unit], as for example, pump storage wound-rotor induction generators/motors have been in used since

1996 in Japan and since 2004 in Germany.

This book deals in depth with both constant- and variable-speed generator systems that operate in

stand-alone and power grid modes.

Chapters have been devoted to topologies, steady-state modeling and performance characteristics,

transients modeling, control, design, and testing, and the most representative and recently proposed

standard electric generator systems.

The book contains most parameter expressions and models required for full modeling, design, and

control, with numerous case studies and results from the literature to enforce the understanding of the

art of electric generators by senior undergraduate and graduate students, faculty, and, especially, industrial

engineers who investigate, design, control, test, and exploit electric generators for higher energy

conversion ratios and better control. This 20-chapter book represents the author’s unitary view of the

multifacets of electric Â�generators with recent developments included.

Chapter 1 introduces energy resources and fundamental solutions for electric energy conversion

problems and their merits and demerits in terms of efficiency and environmental effects. In Chapter 2,

a broad classification and principles of various electric generator topologies with their power ratings

and main applications are presented. Constant-speed-synchronous generators (SGs) and variable-speed

wound-rotor induction generators (WRIGs); cage rotor induction generators (CRIGs); claw pole rotors;

induction; PM-assisted synchronous, switched reluctance generators (SRGs) for vehicular and other

xvi Preface to the First Edition

applications; PM synchronous generators (PMSGs); transverse flux (TF); and flux reversal (FR) PMSGs,

and, finally, linear motion PM alternators are all included.

Chapter 3 treats the main prime movers for electric generators from topologies to basic performance

equations and practical dynamic models and transfer functions.

Steam, gas, hydraulic, and wind turbines and internal combustion (standard, Stirling, and diesel)

engines are dealt with. Their transfer functions are used in subsequent chapters for speed control in

Â�corroboration with electric generator power flow control.

Chapters 4 through 8 deal with SGs steady state, transients, control, design, and testing with plenty of

numerical examples and sample results that cover the subject comprehensively.

This part of the book is dedicated to electric machines and power systems professionals and industries.

Chapters 9 through 11 deal with WRIGs that have a bidirectional rotor connected AC–AC partial

rating PWM converter for variable-speed operation in stand-alone and power grid modes. Steady-state

transients (Chapter 9), vector and direct power control (Chapter 10), and design and testing (Chapter 11)

are treated in detail with plenty of applications and digital simulation and test results to facilitate indepth

assessment of WRIG systems currently built from 1 MVA to 400 MVA per unit.

Chapters 12 and 13 discuss cage rotor induction generators (CRIG) in self-excited modes used as

power grid and stand-alone applications with small speed regulation by a prime mover (Chapter 12)

or with full-rating PWM converters connected to a stator and wide-variable speed (Chapter 13) with

± 100% active and reactive power control and constant (or controlled) output frequency and voltage in

both power grid and stand-alone operations.

Chapters 9 through 13 are targeted to wind, hydro, and, in general, to distributed renewable power

system professionals and industries.

Chapters 14 through 17 deal with representative electric generator systems proposed recently for

integrated starter alternators (ISAs) on automobiles and aircraft, all operating at variable speed with

full power ratings electronics control. Standard (and recently improved) claw pole rotor alternators

(Chapter 14), induction (Chapter 15), PM-assisted synchronous (Chapter 16), and switched reluctance

(Chapter 17) ISAs are discussed thoroughly. Again, with numerous applications and results, from topologies,

steady state, and transients performance, from modeling to control design and testing for the very

challenging speed range constant power requirements (up to 12 to 1) typical to ISA. ISAs have reached

the markets, used on a mass-produced (since 2004) hybrid electric vehicles (HEVs) for notably higher

mileage and less pollution, especially for urban transport.

This part of the book (Chapters 14 through 17) is targeted at automotive and aircraft professionals and

industries.

Chapter 18 deals extensively with radial and axial air gaps, surfaces, and interior PM rotor permanent

magnet synchronous generators that work at variable speed and make use of full power rating electronics

control. This chapter includes basic topologies, thorough field and circuit modeling, losses, performance

characteristics, dynamic models, and bidirectional AC–AC PWM power electronics control in

power grid and in stand-alone applications with constant DC output voltage at variable speed. Design

and testing issues are included, and case studies are treated using numerical examples and transient

performance illustrations.

This chapter is directed at professionals interested in wind and hydraulic energy conversion, generator

set (stand-alone) with power/unit up to 3–5 MW (from 10 rpm to 15 krpm) and 150 kW at 80 krpm

(or more).

Chapter 19 investigates with numerous case study designs two high-torque density PM synchronous

generators (transverse flux [TFG] and flux reversal [FRG]), introduced in the last two decades that take

advantage of non-overlapping multipole stator coils. They are characterized by lower copper losses/N m

and kg/N m and find applications in very-low-speed (down to 10 rpm or so) wind and hydraulic turbine

direct and transmission drives, and medium-speed automotive starter-alternators.

Chapter 20 investigates linear reciprocating and linear progressive motion alternators. Linear reciprocating

PMSGs (driven by Stirling free-piston engines) have been introduced (up to 350 W) and are

Preface to the First Edition xvii

currently used for NASA’s deep-mission generators that require fail-proof operation for 50,000 h. Linear

reciprocating PMSGs are also pursued aggressively as electric generators for series (full electric propulsion)

vehicles for power up to 50 kW or more; finally, they are being proposed for combined electric

(1 kW or more) and thermal energy production in residences with gas as the only prime energy provider.

The author thanks the following:

• Illustrious people that have done research, wrote papers, books, patents, and built and tested

electric generators and their control over the last decades for providing the author with “the air

beneath his wings”