Influence of Saliency Ratio (Xd/Xq) on the Performance of Three-phase Synchronous Reluctance Generators
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 equation 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.
TABLE OF CONTENTS
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
INTRODUCTION
Electrical machines are devices that convert electrical energy to mechanical energy and vice versa. There are two major types of electrical machines by operation: Electric motors and generators. Electric motors convert electrical energy to mechanical energy while electric generators convert mechanical energy to electrical energy.
Electric generators can be classified into two: Alternating current (A.C) generators also known as “alternator” and direct current (D.C) generators.
A.C generator (alternator) can further be classified into two: Induction and synchronous generators. The synchronous generator is one of the first and most well-known synchronous machine types.
It was in the beginning common in MW-size power range, but is nowadays mainly used for different power range machines. Induction generators need no excitation equipment, as it can be driven from the grid. They are classified as self-excited generators.
The synchronous machines have still a number of important advantages which makes them very interesting. To this counts high efficiency, robustness and good controllability. In the upper power range, they are the only option. It can therefore be expected that the synchronous generator will continue to play an important role, also in the future.
High speed synchronous generator driven by steam turbines differ considerably in their construction from the slow engine driven machines and are often described as “flywheel-type”.
There are two basic constructions: Machines with a cylindrical rotor and machines with a salient-pole rotor. For mechanical reasons, the cylindrical rotor is preferred for two poles machines because of the large centrifugal forces that arise.
The salient-pole rotor is usually the more efficient solution for machines with four poles and upwards, both for cost reasons and performance reasons. The rotor can be made of either laminated xxi steel or solid iron.
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CSN Team.
