Key Features:
No. of pages: 208
No. of chapters: 5
Abstract:
A Pulsewidth Modulated Voltage-Fed Inverter Vector-Controlled Permanent Magnet Synchronous Motor (PMSM) Drive based on Hysteresis Current Control (HCC) is presented in this work. A detailed conceptual dq modelling of the PMSM was undertaken in the rotor reference 26 frame for open loop studies, thereby setting the pace for the variable speed drive (VSD) of the PMSM which, inherently, is not capable of variable speed operation. Subsequently, vector control by Field Orientation Control (FOC), is used to decouple the flux and torque producing stator current components of the PMSM thereby permitting independent and precise control of flux and torque as obtainable in separately excited dc machines.
A complete closed loop control system employing an outer PI speed controller and an inner hysteresis current controller was implemented to realize this speed-controlled drive. Since torque can be made proportional to current either in the stationary or rotor reference frames and effective control of current gives effective control of torque, speed, and position, the HCC strategy is aimed at ensuring that the actual motor phase currents track their respective sinusoidal references. The HCC algorithm was developed and employed for the logical firing of the power semiconductor switches of the inverter.
The control algorithm was optimised to obtain fast speed response, while maintaining effective current and torque tracking for all practical speed inputs namely Constant, Step and RAMP reference speed inputs. The optimal control variables were identified with emphasis on effective current and torque tracking. Four quadrant operation of the PMSM was also implemented as obtains in numerous applications in industry where controlled starts and stops are required in both forward and reverse directions. Compared to the standard AC6 of MATLAB Simpower systems, the developed model achieved rise time and settling time of 0.0108 seconds and 0.0143 seconds respectively while the corresponding values for AC6 model are 0.1944 seconds and 0.1984 seconds respectively. This, clearly, shows that the developed model has an enhanced speed response.
Table of Content:
APPROVAL PAGE .......................i
CERTIFICATION PAGE .......................ii
TITLE PAGE .......................iii
DEDICATION .......................iv
ACKNOWLEDGEMENT .......................v
TABLE OF CONTENTS .......................vi
LIST OF SYMBOLS .......................xi
LIST OF ABBREVIATIONS .......................xiv
LIST OF FIGURES .......................xvi
LIST OF TABLES .......................xxiv
ABSTRACT .......................xxv
CHAPTER ONE: INTRODUCTION .......................1
1.0 Introduction .......................1
1.1 PMSM Compared to Other AC Machines .......................2
1.2 Characteristics of Permanent Magnet Materials .......................4
1.3 Classification of Permanent Magnet Motors .......................6
1.4 Classification of Permanent Magnet Synchronous Motor (PMSM) 7
1.5 Research Objectives .......................10
1.6 Thesis Arrangement .......................11
CHAPTER TWO: LITERATURE REVIEW .......................14
CHAPTER THREE: THE PERMANENT MAGNET SYNCHRONOUS MACHINE 52
3.1 D-Q Modelling of Permanent Magnet Synchronous Machine using Two Phase Machine .......................52
3.1.1 Derivation of Inductances as a function of Rotor Position .......................55
3.1.2 Transformation to Rotor Reference Frame .......................58
3.2 Three Phase Permanent Magnet Synchronous Motor Model .......................60
3.3 Development of the PMSM Power and Torque Relationships .......................63
3.4 Steady State Torque Characteristics .......................66
3.5 Equivalent Circuit Representation of PMSM .......................69
3.6 Open Loop Line-Start Permanent Magnet Synchronous Motor .......................71
3.6.1 Discussion of Results .......................74
CHAPTER FOUR: FEATURES AND CONTROL OF THE THREE PHASE VOLTAGE-FED INVERTER FOR AC DRIVES .......................78
4.1 Adjustable Speed Drives (ASD) .......................78
4.2 The Three Phase Inverter .......................80
4.2.1 Six-Step Inverter Operation .......................82
4.2.2 Sinusoidal Pulsewidth Modulation (SPWM) of Three Phase Voltage Source Inverter .......................90
4.2.3 Space Vector Representation of Voltage Source Inverter Output Voltages 96
4.3 Natural Regular Sampled Pulsewidth Modulation of Three Phase Voltage Source Inverter .......................102
4.4 Hysteresis Current Control Strategy .......................106
4.5 Four Quadrant Torque Speed Characteristics .......................109
CHAPTER FIVE: PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL 112
5.1 Vector Control in AC Machines versus Control of Separately Excited DC Machines .......................112
5.2 Vector Control for Permanent Magnet Synchronous Motor .......................112
5.2.1 Electromagnetic Torque under Vector Control .......................115
5.3 General Schematic of the Speed-Controlled Drive System .......................118
5.3.1 Description of the General Schematic of the Speed-Controlled Drive System 119
5.3.1.1 Reference Current Estimation .......................120
5.3.1.2 Inverter Switch Gating Voltage Signal Estimation .......................121
5.4 Drive Performance with Sample PMSMs .......................122
5.4.1 Drive Performance for Motor One (Rated Torque 10Nm) .......................124
5.4.2 Drive Performance for Motor Two (Rated Torque 26Nm) .......................126
5.5 Drive Performance under various Speed Reference Inputs for Sample Motor Two .......................128
5.5.1 Case One: Drive Performance with Constant Reference Speed Input (200 rpm) .......................129
5.5.1.1 Highlights on Hysteresis Current Control action and the Inverter Switching 132
5.5.2 Case Two: Drive Performance with Step Reference Speed Input (0rpm to 200rpm to 400rpm to -400rpm to -200rpm to 0rpm) .......................140
5.5.3 Case Three: Drive Performance with RAMP Reference Speed Input (0 rpm to 500 rpm to -500 rpm to 0 rpm) .......................144
5.6 Drive Performance under Step Speed Transition for Four Quadrant Operation (500 rpm to -500 rpm to 500 rpm) .......................147
5.7 Drive Speed Response Compared with Response of SIMPOWER AC6 150
CHAPTER SIX: CONCLUSION AND RECOMMENDATIONS FOR FUTURE WORK 156
6.1 Conclusion .......................156
6.2 Recommendations for Future Work .......................158
REFERENCES .......................161
Appendix 1: PMSM Parameters for Open Loop Studies .......................175
Appendix 2: Codes for Steady State Torque Characteristics .......................176
Appendix 3: Embedded MATLAB Function Block .......................177
Appendix 4: Embedded MATLAB Function Codes .......................178
Appendix 5: Six Step Inverter Model .......................179
Appendix 6: SPWM Inverter Model .......................180
Appendix 7: PMSM Ratings ....................... 181
Appendix 8: Simulink Model of the Speed-Controlled Drive System .......................182
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