Influence of Saliency Ratio (Xd, Xq) on the Performance of Three-Phase Synchronous Reluctance Generators.

ABSTRACT 

In the study of the influence of saliency ratio (L /L ) on the performance of a synchronous reluctance generator (SRG), this project investigates two typical generator rotor designs: Generator with cage and without cage otherwise known as cage and cageless rotor respectively. A special attention had been paid to the possible rotor geometries of synchronous reluctance machine, SRM. This ratio can directly influence our insight into the machine’s potential abilities. From the studies of three phase SRG, a modeled direct and quadrature axes equations for both rotor configurations are presented for dynamic simulation. Basic parameters and generator performance, such as phase voltage and current build-up, output power with load current, peak voltage with load current, reactive power with load current are compared for both rotor designs. These analyses from the simulation were carried out by Embedded MATLAB Function. It was observed from capacitor selection that the capacitors ranging from 50 to 120µF produced a suitable voltage build-up in every case without exceeding the current-carrying capacity of the winding coil. Another observation from the result is that, cage-less-rotor can only be excited with much lower capacitor values, between 40 and 65µF. This indicates that cage-less-rotor produces a lower voltage, lower load current and yields lower output power. The saliency ratio obtained under rotor geometry modifications does not surpass 7, while the longitudinal magnetization reactance, X    is reduced by at least 20% with respect to value for uniform air-gap. Different values of saliency ratios were investigated through MATLAB simulation by dividing the measured quadrature axis magnetizing reactance, X    with arithmetic progressing numbers ranging from 2, 2.5, 3, 3.5 to 6.5 which mathematically increases the direct axis magnetizing reactance value, X    of saliency ratios by 2X   , 2. 5X   , 3X   , 3.5X   , to 6.5X   . The higher the saliency ratio, the higher the power factor and output power. The saliency ratio is the most importance parameter of a synchronous reluctance generator which is directly proportionally to power factor and output power.

TABLE OF CONTENTS

CONTENTS PAGES

Cover page…………………………………………………………………………………………i

Approval page……………………………………………………………………………………..ii

Title page………………………………………………………………………………………….iii

Certification……………………………………………………………………………………….iv

Dedication………………………………………………………………………………………....v

Acknowledgement………………………………………………………………………………...vi

Abstract…………………………………………………………………………………………...viii

Table of contents……………………………………………………………………………….....ix

List of Figures…………………..…...…………………………………………………………....xiv

List of Table…………………………………………………………………...…………….…...xiv

CHAPTER ONE:

INTRODUCTION

1.1 Background of the work……………………………………………………………… 1

1.2 Self excited A.C generator…………………………………………………………… 2

1.3 Saliency ratio of salient pole synchronous machine………………………………… 3

1.4 Improvement of the output power of salient pole synchronous machine………….... 5

1.5 Aims and objectives of the project…………………………………………………… 5

1.6 Motivation for the project………………………………………………….................... 5

1.7 The outline of the thesis work…………………………………………………………..5

CHAPTER TWO:

LITERATURE REVIEW

2. 1 Introduction on synchronous generator…………………………………………… 7

2.2 The rotor structure………………………………………………………………….7

2.2.1 The cylindrical rotor…………………………………………………………….... 7

2.2.2 The salient pole rotor…………………………………………………………….. 8

2.3 The stator / armature winding…………………………………………………… 9

2.3.1 Winding types……………………………………………………………………. 9

2.3.1.1 Double layer windings……………………………………………………….….. 9

2.3.2 Number of coils…………………………………………………………………..9

2.3.3 Conductor design………………………………………………………………... 10

2.3.4 Skewing…………………………………………………………………………. 10

2.4 Rating of synchronous generator (alternator)…………………………………... 10

2.5 Alternator on load……………………………………………………………….. 10

2.6 Voltage regulator……………………………………………………………..…. 11

2.7 Two-reactance concept for salient pole synchronous machine..…………….........11

2.8 Losses and efficiency………………………………………………………..….. 12

2.9 The synchronous reluctance machine……………………………………..…...... 12

2.10 Advantages of synchronous reluctance machine………………………..……… 13

2.11 The working principle of synchronous reluctance generator…………..………. 14

2.12 Saliency ratio optimization…………………………………………….………... 15

2.12.1 The conventional rotor………………………………………………..………….15

2.12.2 The segmental rotor…………………………………………………..…………. 16

2.12.3 The channel segment rotor…………………………………………..…………. 17

2.12.4 The flux barrier rotor……………………………………………….…………… 18

2.12.5 The layer type flux barrier………………………………………………………. 19

2.12.6 The axially laminated anisotropic rotor……………………….………………....... 20

2.13 The evolution of anisotropic rotor geometry and classification….……………. 21

2.14 TLA and ALA comparison…………….…………………………………………. 25

2.15 The parametric effects of saliency ratio on the SRG……………………………... 27

2.15.1 Air gap length…………………………………………………………………….. 27

2.15.1.1 Machine magnetizing inductances……………………………………………...... 28

2.15.2 Number of turns of the winding………………………………………………....... 28

2.15.3 Air gap/slot depth ratio………………………………………………………......... 29

2.15.4 Pole arc/pole pitch ratio…………………………………………………………… 29

CHAPTER THREE

MATHEMATICAL MODEL OF SYNCHRONOUS RELUCTANCE GENERATOR

3.1 Modeling of synchronous reluctance generator..………………………………… 30

3.1.1 Cageless-rotor synchronous reluctance generator…….………………………….. 30

3.1.1.1 Voltage equations………………………………………………………………….. 30

3.1.2 Load model equations of synchronous reluctance generator…………………….. 32

3.1.3 Capacitance excitation model equations of synchronous reluctance generator…. 34

3.1.4 Reference frame transformation…………………………………………………… 35

3.2 The steady state at power grid (cageless-rotor synchronous reluctance generator at standstill) …………………………………...………………………. 39

3.3 Cage-rotor synchronous reluctance generator ………………………………………. 40

3.3.1 Voltage equations …………………………………………………………………. 40

3.3.2 The d-q model of cage-rotor SRG…………………………………………………. 41

3.3.3 The steady state of cage-rotor capacitor excited synchronous reluctance generator.. 44

3.3.4 Relationship between 3-phase and orthogonal quantity in stationary and synchronous reference frame……………………………………………………….. 45

3.4 Power equation…………………………………………………………………….. 47

CHAPTER FOUR

DYNAMIC SIMULATION OF ROTOR CONFIGURATION SYNCHRONOUS

RELUCTANCE GENERATOR

4.1 Simulation tools……………………………………………………………………… 49

4.2 Simulation of cage and cageless-rotor synchronous reluctance generator using Embedded MATLAB Function Block………………………………………… 49

4.3 Simulation Results……………………………………………………...…………….. 49

4.4 Analysis of Results…………………………………………………………………… 49

CHAPTER FIVE

Conclusion and Recommendation

5.1 Conclusion and recommendation……………………………………………………. 68

 References…………………………………………………………………………… 70

 Appendix 1……………………………………………………….................................75

 Appendix 2…………………………………………………………………………….76

 Appendix 3…………………………………………………………………………….77

 Appendix 4…………………………………………………………………………….80