MASTER OF SCIENCE IN ELECTRICAL ENGINEERING
2016
HIGH PERFORMANCE OF DIRECT TORQUE CONTROL
FOR FIVE-PHASE INDUCTION MACHINE
HIGH PERFORMANCE OF DIRECT TORQUE CONTROL FOR FIVE PHASE INDUCTION MACHINE
LOGAN RAJ A/L LOURDES VICTOR RAJ
A thesis submitted
in fulfillment of the requirements for the degree ofMaster of Science in Electrical Engineering
Faculty of Electrical Engineering
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
APPROVAL
I hereby declare that I have read this dissertation/report and in my opinion this dissertation/report is sufficient in terms of scope and quality as a partial fulfillment of Master of Science in Electrical Engineering (Power Electronics and Drives).
DECLARATION
I declare that this thesis entitled “High Performance of Direct Torque Control for Five-Phase Induction Machine” is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree.
DEDICATION
To my parents,
supervisor Dr Auzani bin Jidin, and friend Sundram Rahmalingam for their support, care and patience.
ABSTRACT
ABSTRAK
ACKNOWLEDGEMENTS
I acknowledge, with gratitude, my debt of thanks to Dr. Auzani bin Jidin for his guidance, ancouragement and patience on assisting me throughout my research and towards the completion of this thesis.
I would also like to thank everyone who have contributed to this thesis particularly my friend and co-researcher Sundram Rahmalingam for their undisputed support and encouragament.
This research was fully supported by Universiti Teknikal Malaysia Melaka. I am grateful to this institution for providing me the platform and support through scholarship and sponsorship to complete this study.
Finally, I would like to thank my parents and family members for their moral support encouragement and tollerence throughout my study.
TABLE OF CONTENTS
LIST OF APPENDICES xvii
LIST OF SYMBOL xviii
LIST OF ABBREVIATIONS xx
LIST OF ACHIVEMENTS xxii
CHAPTER
1. INTRODUCTION 1
1.1 Research Background 1
1.2 Motivation of Research 5
1.3 Problem statement 5
1.3.1 Large Torque Ripple 6
1.3.2 High Switching Frequency/Losses 6 1.3.3 Slow Torque Dynamic Control 7
1.4 Objectives 7
2.2 Principle of Direct Torque Control (DTC) of Three-
Phase Induction Motors 14
2.2.1 Mathematical Modelling of Three-phase
Induction Machines. 15 2.3 Principle of Direct Torque Control with Hexagonal
Flux Control for Three-Phase Induction Motors 33 2.3.1 Hexagonal Flux Control based on the Hysteresis
Controllers 33
2.3.2 Hexagonal Flux Control based on the Modification of
Torque Error Status 37
2.4 Direct Torque Control of Five-Phase Induction Motors 48 2.4.1 Comparison of DTC and FOC 49 2.4.2 Conceptual of DTC of Five-Phase Induction Machines 53
2.5 Conclusion 69
3. RESEARCH METHODOLOGY 70
3.1 Introduction 70
3.2 Mapping of Voltage Vectors for Five-Phase Inverter 70 3.2.1 Five-Phase Voltage Source Inverter 71 3.2.2 Space Voltage Vector of Five-phase Voltage 74 3.2.3 d- and q- Components of Stator Voltage 76
3.2.4 Voltage Vectors of Five-phase Inverter on the
Voltage Vector Plane 78
3.3 An Improved Switching Strategy 80
3.3.1 Investigation on Effects of Selecting Different Switching
Voltage Vector Options on Torque Control Behaviour 80 3.3.1.1 Analysis on Torque Dynamic Control using
Torque Rate Equation 81
3.3.1.2 Analysis on Torque Control Capability based on
the Maximum Slip Angular Frequency 83 3.3.1.3 Analysis on Torque Slopes for Various Motor
Operating Conditions 86
3.3.2 Identification of Optimal Voltage Vectors 88 3.3.2.1 Improvement 1: Reduction of Switching Frequency 92 3.3.2.2 Improvement 2: Reduction of Torque Ripple 99 3.3.2.3 Improvement 3: Fast Torque Dynamic Control 105 3.4 Definition of Flux Sectors for Selecting Optimal Vectors 107 3.5 Look-up Table for Selecting Optimal Voltage Vectors 109
3.6 Proposed Control Structure 112
3.7 Simulation Model of DTC of Five-Phase Induction Machine 114 3.7.1 Five-Phase induction machine 117 3.7.2 Simulation Model of Five-Phase inverter 119 3.7.3 Simulation Model of d- and q-Components of Stator Voltage 122 3.7.4 Simulation Model of d- and q-Components of Stator Current 122 3.7.5 Simulation Model of Flux and Torque Estimation for
4.2 Performance Analysis of Torque Ripple, Switching Frequency
and Torque Dynamic Control via Simulations 138 4.2.1 Improvement 1: Reduction of Torque Ripple 140 4.2.2 Improvement 2: Minimization of Switching Frequency 147 4.2.3 Improvement 3: Fast Torque Dynamic Control 152 4.3 Verification Improvements via Experimental Results 159 4.3.1 Reduction of Torque Ripple and Switching Frequency 160 4.3.2 Improved Torque Dynamic Control 171
4.4 Conclusion 174
5. CONCLUSION AND RECOMMENDATIONS 175
5.1 Conclusions 175
5.2 Constrains and Limitations of Research 177
5.3 Future Works 178
REFERENCES 181
APPENDICES 193
LIST OF TABLES
TABLE TITLE PAGES
2.1 Selection of Voltage Vectors as Proposed in
(Takahashi and Noguchi, 1986) 30
2.2 Table 2.2 : The look up table proposed in (Toliyat and Huangsheng, 2000) (a) Longgest Voltage Vector
(b) Medium Voltage Vector (c) Shortest Voltage Vector 56
2.3 Stator Flux and Torque Variation for Different Voltage Vectors
for Sector I, as Reported in (Mythili and Thyagarajah, 2005) 58
3.1 Classification of Voltage Vectors of Five-Phase Inverter 78
3.2 Look-up table of DTC with Circular Flux Control
(Optimal Vector Selection) 110
3.3 Look-up table of DTC with Decagonal Flux Control and with
Optimal Vector Switching 111
3.4 Parameters of 5-Phase Induction Machine 136
4.1 Parameters of Five-Phase Induction Motor 139
LIST OF FIGURES
FIGURE TITLE PAGE
1.1 DTC Structure Proposed in (Takahashi and Noguchi, 1986) 2
1.2 Control Structure of DTC of Five-Phase Induction Motor 4
1.3 Flow chart of Research Methodology 10
2.1 Block Diagram of the Mathematical Modelling of an Induction
Machine 17
2.2 A Three-Phase Voltage Source Inverter 19
2.3 Voltage Vectors (including Switching States Information) on the
Voltage Vector Plane 19
2.4 Trajectory of Stator Flux Vector in DTC 21
2.5 A Decoupled Control Structure with a Look-up Table for
Establishing Simultaneous Control of Stator Flux and Torque 26
2.6 Production of Flux Error Status σ_φ and Torque Error Status σ_T using (a) 2-Level Hysteresis Comparator and (b) 3-level Hysteresis
Comparator, Respectively 27
2.7 Typical Waveforms of the Torque, the Torque Error, the Stator Flux, the Flux Error, the Torque Error Status and the Flux Error Status including Voltage Vectors Selection for Controlling the
Stator Flux and Torque in Sector III 29
2.8 Structure of Direct Torque Control (DTC) based Induction
Machine, as Proposed in (Takahashi and Noguchi, 1986) 31
2.9 Structure of Direct Self Control (DSC) based Induction
Machine, as Proposed in (Depenbrock, 1988) 35
2.10 Simulation Result of the Typical Waveforms in Direct Self Control 36
2.11 A Hexagonal Flux Shape obtained in DSC Scheme 37
2.12 Structure of DTC with Inclusion of Modification of Torque Error
Status, as Proposed in (Jidin et al., 2011a) 39
2.13 The Modification Block for Hexagonal Flux Operation 40
2.14 Modified Flux Error Status ����� for Every Sub Sector
(in Each Sector) for Hexagonal Flux Control 41
2.15 The Shrinking of Hexagonal Flux Locus 42
2.16 Flux Keeps the Increase as it Enters to Sub sector ii Until it
Reaches to the Point c. (i.e. path b-c) with the ����� = 0 43
2.17 State Diagram of Finite State Machine that Establishes the Modified Flux Error Status for Proper Hexagonal Flux Locus
Operation (as Proposed in (Jidin et al., 2011a)). 44
2.18 Effects of Selecting Different Switching under Dynamic Condition. (a) Stator Voltage Vector in Stator Flux (b) Comparison of the Load Angle, δsr generated by the Same Magnitude of Appropriate
Voltage Vectors. 47
2.19 Structure of Field Oriented Control of Five-Phase Induction
Machine 51
2.20 Structure of Direct Torque Control of Five-Phase Induction
Machine 52
2.21 A Five-Phase Voltage Source Inverter Connected to a Five-Phase
Induction Machine 54
2.22 32 Voltage Vectors (on the voltage vector plane) offered in a
Five-Phase Inverter 54
2.23 Control of Torque is Directly Influenced by the Variation of Angle δsr due to the Irregular Motion of Stator Flux Vector
(e.g. in Sector I). 58
2.24 Hysteresis Comparators for (a) Torque Controller with 7- Level
Hysteresis Band (b) Flux Controller with 2-Level Hysteresis Band 61
2.25 Simulation Results of Torque, Torque Error, Torque Error Status, Stator Currents and Phase Voltage obtained in Five-Phase DTC
(Raj et al., 2013) 62
2.26 Zoomed Images for Simulation Results of Torque and Torque Error as obtained in Fig. 2.24, for (a) Region 1, (b) Region 2
and (c) Region 3. 63
2.27 Simulation Results of Torque, Torque Error, Torque Error Status, Stator Currents and Phase Voltage obtained in Five-
Phase DTC (Raj et al., 2013), at a Sampling Time 50 �s 65
2.28 Zoomed Images for Simulation Results of Torque and Torque Error as obtained in Fig. 2.26, for (a) Region 1, (b) Region 2
and (c) Region 3 66
2.29 Torque Dynamic Control with Selection of Non-Optimal Voltage
Vectors 68
3.1 Simplified Five-Phase Inverter Connected to a Five-Phase
Induction Machine 72
3.2 Simplified Five-Phase Inverter with Consideration only for any
Phase (or �-phase) 73
3.3 Definition of Phase Vectors in (3.4). 75
3.4 Vector Units for Each Phase on the Rectangular Coordinates 77
3.5 32 Voltage Vectors (on the Voltage Vector Plane) offered in a Five- Phase Inverter, as shown in Fig. 2.20 79
3.6 Space Vectors of the Applied Voltage, the Stator Flux and the
Rotor Flux 82
3.7 Phasor Diagrams of Vectors of Stator Voltage, Ohmic Voltage Drop and Back-Emf for (a) Low Speed Operation and (b) Base
Speed Operation 87
3.8 Analysis of Torque Dynamic or Slope based on Current Changes
for Different Switching of Voltage Vectors in Sector III 90
3.9 Control of Torque using the Proposed Method (Dotted Line) and the Conventional DTC (Solid Line) at Low Speed Operations. (a) the Selection of Voltage Vectors and (b) the Variation of Torque
inthe Hysteresis Band 96
3.10 Control of Torque using the Proposed Method (Dotted Line) and the Conventional DTC (Solid Line) at Medium Speed Operations. (a) the Selection of Voltage Vectors and (b) the Variation of
Torque in the Hysteresis Band 97
3.11 Control of Torque using the Proposed Method (Dotted Line) and the Conventional DTC (Solid Line) at High Speed Operations. (a) the Selection of Voltage Vectors and (b) the Variation of
Torque in the Hysteresis Band 98
3.12 Control of Torque using the Proposed Method (Dotted Line) and the Conventional DTC (solid line) at Low Speed Operations. (a) the Torque Waveforms (b) the Torque Error Waveforms, and (c)
the Torque Error Status Waveforms 102
3.13 Control of Torque using the Proposed Method (Dotted Line) and the Conventional DTC (solid line) at Medium Speed Operations. (a) the Torque Waveforms (b) the Torque Error
Waveforms, and (c) the Torque Error Status Waveforms 103
3.14 Control of Torque using the Proposed Method (Dotted Line) and the Conventional DTC (solid line) at High Speed
Operations. (a) the Torque Waveforms (b) the Torque
Error Waveforms, and (c) the Torque Error Status Waveforms 104
3.15 Performance Comparison of Torque Dynamic Control for (a) Conventional DTC with a Circular Flux Operation (b)
Proposed DTC with a Decagonal Flux operation 106
3.16 Flux Sector Definition and Optimal Voltage Vector Selection for
Circular Flux Locus 108
3.17 Flux Sector Definition and Optimal Voltage Vector Selection for
Decagonal Flux Locus 109
3.18 Control structure of the proposed circular flux DTC 113
3.19 Control structure of the proposed decagonal flux DTC 113
3.20 Complete simulation model of proposed circular flux DTC 115
3.21 Complete simulation model of proposed decagonal flux DTC 116
3.22 Simulation model of 5-Phase induction machine 117
3.23 Detailed simulation model of 5-Phase induction machine 118
3.24 Definition of Phase Voltage and Pole Inverter Voltage (e.g.
in Phase �) based on Simplified Five-Phase Inverter 120
3.25 Simulation Model of Five-Phase Inverter 121
3.26 Simulation Model of �- and �-Component of Voltage 122
3.27 Simulation Model of �- and �-Component of Current 123
3.28 Simulation model of flux and torque estimation 124
3.29 Simulation block of sector definition 124
3.30 Flow chart of sector definition for circular flux 125
3.31 Flow chart of sector definition for decagonal flux 126
3.32 Block diagram of Experimental Setup 127
3.33 Photography of Experimental setup of DTC for 5-Phase Induction
Machine 128
3.34 FPGA Altera DE0 board 130
3.35 Waveform with time delay applied 131
3.36 Current sensor 132
3.37 Schematic diagram of current sensor 133
3.38 Schematic diagram of gate driver 134
3.40 Five Phase Induction Machine 136
4.1 Waveforms of Torque, Stator flux, Phase Stator Currents and Stator Voltage at Low-Speed for (a) the DTC2, and (b) the DTC1 143
4.2 Waveforms of Torque, Stator flux, Phase Stator Currents and Stator Voltage at Medium-Speed for (a) the DTC2, and (b)
the DTC1 144
4.3 Waveforms of Torque, Stator flux, Phase Stator Currents and Stator Voltage at High-Speed for (a) the DTC2, and (b) the DTC1 145
4.4 Mapping of Switching Vectors on the d- and q-Axis Coordinate for (a) the DTC1 at Every Different of Speed Operations, (b) the DTC2at High-Speed, (c) the DTC2 at Medium-Speed, and (d)
the DTC2 at Low-Speed 146
4.5 Comparison of Switching Frequency Performance Resulted in Torque and Currents Waveforms for (a) Low-Speed, (b) Medium-
Speed and (c) High-Speed 151
4.6 Waveforms of Torque, Stator flux and d- and q-Components of Stator Currents when a Step Change of Reference Torque is
Applied, at Low-Speed for (a) DTC1, (b) DTC3, (c) DTC4 155
4.7 Comparison of Torque Dynamic Control Performance, when a Step Change of Reference Torque is Applied, at Low-Speed for (a)
DTC1, (b) DTC3, and (c) DTC4 156
4.8 Waveforms of Torque, Stator flux and d- and q-Components of Stator Currents when a Step Change of Reference Torque is
Applied, at High-Speed for (a) DTC1 and (b) DTC3 157
4.9 Comparison of Torque Dynamic Control Performance, when a Step Change of Reference Torque is Applied, at High-Speed
for (a) DTC1, and (b) DTC3 158
4.10 Profiles of Current Components when a Step Change of Reference
Torque is Applied, at High-Speed for (a) DTC1, and (b) DTC3 158
4.11 Experimental result of Torque, Stator flux, and Stator Voltage at
Low-Speed for DTC1 and DTC2 (a) Overall, and (b) Zoomed 160
4.12 Experimental Results of Torque, Stator Flux and Stator Voltage
at Low-Speed for DTC1 and DTC3 (a) Overall and (b) Zoomed 162
4.13 Simulation Results of Torque, Stator Flux and Stator Voltage
at Low-Speed for DTC1 and DTC2 (a) Overall and (b) Zoomed 163
4.14 Simulation Results of Torque, Stator Flux and Stator Voltage
at Low-Speed for DTC1 and DTC3 (a) Overall and (b) Zoomed 164
4.15 Experimental Results of Torque, Stator Flux and Stator Voltage
at High-Speed for DTC1 and DTC2 (a) Overall and (b) Zoomed 167
4.16 Experimental Results of Torque, Stator Flux and Stator Voltage
at High-Speed for DTC1 and DTC3 (a) Overall and (b) Zoomed 168
4.17 Simulation Results of Torque, Stator Flux and Stator Voltage
at High-Speed for DTC1 and DTC2 (a) Overall and (b) Zoomed 169
4.18 Simulation Results of Torque, Stator Flux and Stator Voltage at
High -Speed for DTC1 and DTC3 (a) Overall and (b) Zoomed 170
4.19 Experimental Results of Torque, Stator Flux and Phase Voltage 172
in DTC1
4.20 Experimental Results of Torque, Stator Flux and Phase Voltage 172
in DTC3
4.21 Comparison of Torque Dynamic Control Performance Between
DTC1and DTC3 173
4.22 Trajectory of Stator Flux (a) Circular Locus in DTC1 and (b)
Decagonal Locus in DTC3 174
LIST OF APPENDICES
APPENDIX TITLE PAGE
A Matlab source code listing 192
B VHDL source code listing 202
LIST OF ABBREVIATIONS
AC - Alternating Current ADC - Analog Digital Converter DAC Digital Analog Converter
DC - Direct current DSC - Direct Self Control DSP - Digital Signal Processor
DT - Sampling period DTC - Direct Torque Control
DTC1 - Conventional DTC of Five Phase Inverter DTC2 - DTC with Optimal Voltage Vector Selection
DTC3 - DTC with Decagonal Flux and Optimal Voltage Vector Selection FPGA - Field Programmer Gate Array
FOC - Field Oriented Control
IGBT - Insulated gate bipolar transistor IM - Induction Motor
LB - Lower band
SVM - Space vector modulated UB - Upper band
