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Advanced Electric Drives: Analysis, Control, and Modeling Using MATLAB / Simulink

ISBN: 978-1-118-48548-4
208 pages
August 2014
Advanced Electric Drives: Analysis, Control, and Modeling Using MATLAB / Simulink (1118485483) cover image

Description

With nearly two-thirds of global electricity consumed by electric motors, it should come as no surprise that their proper control represents appreciable energy savings. The efficient use of electric drives also has far-reaching applications in such areas as factory automation (robotics), clean transportation (hybrid-electric vehicles), and renewable (wind and solar) energy resource management. Advanced Electric Drives utilizes a physics-based approach to explain the fundamental concepts of modern electric drive control and its operation under dynamic conditions. Author Ned Mohan, a decades-long leader in Electrical Energy Systems (EES) education and research, reveals how the investment of proper controls, advanced MATLAB and Simulink simulations, and careful forethought in the design of energy systems translates to significant savings in energy and dollars. Offering students a fresh alternative to standard mathematical treatments of dq-axis transformation of a-b-c phase quantities, Mohan’s unique physics-based approach “visualizes” a set of representative dq windings along an orthogonal set of axes and then relates their currents and voltages to the a-b-c phase quantities. Advanced Electric Drives is an invaluable resource to facilitate an understanding of the analysis, control, and modelling of electric machines.

• Gives readers a “physical” picture of electric machines and drives without resorting to mathematical transformations for easy visualization

• Confirms the physics-based analysis of electric drives mathematically

• Provides readers with an analysis of electric machines in a way that can be easily interfaced to common power electronic converters and controlled using any control scheme

• Makes the MATLAB/Simulink files used in examples available to anyone in an accompanying website

• Reinforces fundamentals with a variety of discussion questions, concept quizzes, and homework problems
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Table of Contents

Preface xiii

Notation xv

1 Applications: Speed and Torque Control 1

1-1 History 1

1-2 Background 2

1-3 Types of ac Drives Discussed and the Simulation Software 2

1-4 Structure of this Textbook 3

1-5 “Test” Induction Motor 3

1-6 Summary 4

References 4

Problems 4

2 Induction Machine Equations in Phase Quantities: Assisted by Space Vectors 6

2-1 Introduction 6

2-2 Sinusoidally Distributed Stator Windings 6

2-2-1 Three-Phase, Sinusoidally Distributed Stator Windings 8

2-3 Stator Inductances (Rotor Open-Circuited) 9

2-3-1 Stator Single-Phase Magnetizing Inductance Lm,1-phase 9

2-3-2 Stator Mutual-Inductance Lmutual 11

2-3-3 Per-Phase Magnetizing-Inductance Lm 12

2-3-4 Stator-Inductance Ls 12

2-4 Equivalent Windings in a Squirrel-Cage Rotor 13

2-4-1 Rotor-Winding Inductances (Stator Open-Circuited) 13

2-5 Mutual Inductances between the Stator and the Rotor Phase Windings 15

2-6 Review of Space Vectors 15

2-6-1 Relationship between Phasors and Space Vectors in Sinusoidal Steady State 17

2-7 Flux Linkages 18

2-7-1 Stator Flux Linkage (Rotor Open-Circuited) 18

2-7-2 Rotor Flux Linkage (Stator Open-Circuited) 19

2-7-3 Stator and Rotor Flux Linkages (Simultaneous Stator and Rotor Currents) 20

2-8 Stator and Rotor Voltage Equations in Terms of Space Vectors 21

2-9 Making the Case for a dq -Winding Analysis 22

2-10 Summary 25

Reference 25

Problems 26

3 Dynamic Analysis of Induction Machines in Terms of dq Windings 28

3-1 Introduction 28

3-2 dq Winding Representation 28

3-2-1 Stator dq Winding Representation 29

3-2-2 Rotor dq Windings (Along the Same dq-Axes as in the Stator) 31

3-2-3 Mutual Inductance between dq Windings on the Stator and the Rotor 32

3-3 Mathematical Relationships of the dq Windings (at an Arbitrary Speed ωd) 33

3-3-1 Relating dq Winding Variables to Phase Winding Variables 35

3-3-2 Flux Linkages of dq Windings in Terms of Their Currents 36

3-3-3 dq Winding Voltage Equations 37

3-3-4 Obtaining Fluxes and Currents with Voltages as Inputs 40

3-4 Choice of the dqWinding Speed ωd 41

3-5 Electromagnetic Torque 42

3-5-1 Torque on the Rotor d -Axis Winding 42

3-5-2 Torque on the Rotor q -Axis Winding 43

3-5-3 Net Electromagnetic Torque Tem on the Rotor 44

3-6 Electrodynamics 44

3-7 d- and q-Axis Equivalent Circuits 45

3-8 Relationship between the dq Windings and the Per-Phase Phasor-Domain Equivalent Circuit in Balanced Sinusoidal Steady State 46

3-9 Computer Simulation 47

3-9-1 Calculation of Initial Conditions 48

3-10 Summary 56

Reference 56

Problems 57

4 Vector Control of Induction-Motor Drives: A Qualitative Examination 59

4-1 Introduction 59

4-2 Emulation of dc and Brushless dc Drive Performance 59

4-2-1 Vector Control of Induction-Motor Drives 61

4-3 Analogy to a Current-Excited Transformer with a Shorted Secondary 62

4-3-1 Using the Transformer Equivalent Circuit 65

4-4 d- and q -Axis Winding Representation 66

4-5 Vector Control with d-Axis Aligned with the Rotor Flux 67

4-5-1 Initial Flux Buildup Prior to t = 0−67

4-5-2 Step Change in Torque at t = 0+68

4-6 Torque, Speed, and Position Control 72

4-6-1 The Reference Current isq t * ( ) 72

4-6-2 The Reference Current isd ( ) 73

4-6-3 Transformation and Inverse-Transformation of Stator Currents 73

4-6-4 The Estimated Motor Model for Vector Control 74

4-7 The Power-Processing Unit (PPU) 75

4-8 Summary 76

References 76

Problems 77

5 Mathematical Description of Vector Control in Induction Machines 79

5-1 Motor Model with the d-Axis Aligned Along the Rotor Flux Linkage λ r-Axis 79

5-1-1 Calculation of ωdA 81

5-1-2 Calculation of Tem 81

5-1-3 d-Axis Rotor Flux Linkage Dynamics 82

5-1-4 Motor Model 82

5-2 Vector Control 84

5-2-1 Speed and Position Control Loops 86

5-2-2 Initial Startup 89

5-2-3 Calculating the Stator Voltages to Be Applied 89

5-2-4 Designing the PI Controllers 90

5-3 Summary 95

Reference 95

Problems 95

6 Detuning Effects in Induction Motor Vector Control 97

6-1 Effect of Detuning Due to Incorrect Rotor Time Constant τr 97

6-2 Steady-State Analysis 101

6-2-1 Steady-State isd /is*d 104

6-2-2 Steady-State isq /is*q 104

6-2-3 Steady-State θerr 105

6-2-4 Steady-State Tem /Te*m 106

6-3 Summary 107

References 107

Problems 108

7 Dynamic Analysis of Doubly Fed Induction Generators and Their Vector Control 109

7-1 Understanding DFIG Operation 110

7-2 Dynamic Analysis of DFIG 116

7-3 Vector Control of DFIG 116

7-4 Summary 117

References 117

Problems 117

8 Space Vector Pulse Width-Modulated (SV-PWM) Inverters 119

8-1 Introduction 119

8-2 Synthesis of Stator Voltage Space Vector vsa 119

8-3 Computer Simulation of SV-PWM Inverter 124

8-4 Limit on the Amplitude ˆVs of the Stator Voltage Space Vectov sa 125

Summary 128

References 128

Problems 129

9 Direct Torque Control (DTC) and Encoderless Operation of Induction Motor Drives 130

9-1 Introduction 130

9-2 System Overview 130

9-3 Principle of Encoderless DTC Operation 131

9-4 Calculation of λs, λ r, Tem, and ωm 132

9-4-1 Calculation of the Stator Flux λ s 132

9-4-2 Calculation of the Rotor Flux λ r 133

9-4-3 Calculation of the Electromagnetic Torque Tem 134

9-4-4 Calculation of the Rotor Speed ωm 135

9-5 Calculation of the Stator Voltage Space Vector 136

9-6 Direct Torque Control Using dq-Axes 139

9-7 Summary 139

References 139

Problems 139

Appendix 9-A 140

Derivation of Torque Expressions 140

10 Vector Control of Permanent-Magnet Synchronous Motor Drives 143

10-1 Introduction 143

10-2 d-q Analysis of Permanent Magnet (Nonsalient-Pole) Synchronous Machines 143

10-2-1 Flux Linkages 144

10-2-2 Stator dq Winding Voltages 144

10-2-3 Electromagnetic Torque 145

10-2-4 Electrodynamics 145

10-2-5 Relationship between the dq Circuits and the Per-Phase Phasor-Domain Equivalent Circuit in Balanced Sinusoidal Steady State 145

10-2-6 dq-Based Dynamic Controller for “Brushless DC” Drives 147

10-3 Salient-Pole Synchronous Machines 151

10-3-1 Inductances 152

10-3-2 Flux Linkages 153

10-3-3 Winding Voltages 153

10-3-4 Electromagnetic Torque 154

10-3-5 dq-Axis Equivalent Circuits 154

10-3-6 Space Vector Diagram in Steady State 154

10-4 Summary 156

References 156

Problems 156

11 Switched-Reluctance Motor (SRM) Drives 157

11-1 Introduction 157

11-2 Switched-Reluctance Motor 157

11-2-1 Electromagnetic Torque Tem 159

11-2-2 Induced Back-EMF ea 161

11-3 Instantaneous Waveforms 162

11-4 Role of Magnetic Saturation 164

11-5 Power Processing Units for SRM Drives 165

11-6 Determining the Rotor Position for Encoderles Operation 166

11-7 Control in Motoring Mode 166

11-8 Summary 167

References 167

Problems 167

Index 169

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Author Information

Ned Mohan is the Oscar A. Schott Professor of Power Electronics at the University of Minnesota. A holder of numerous patents in the field, Mohan is the author of four other books published by Wiley, and is a member of the National Academy of Engineering.
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