OPTIMISING AC ELECTRIC RAILWAY POWER FLOWS WITH POWER ELECTRONIC CONTROL ...

304 Pages·2003·4.39 MB·English

OPTIMISING AC ELECTRIC RAILWAY POWER FLOWS
WITH POWER ELECTRONIC CONTROL

by

THANATCHAI KULWORAWANICHPONG

A thesis submitted to
The University of Birmingham
For the degree of
DOCTOR OF PHILOSOPHY

Department of Electronic, Electrical and Computer Engineering
School of Engineering
The University of Birmingham
November 2003
University of Birmingham Research Archive

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SYNOPSIS

The latest generation of AC-fed traction drives, employing high-speed switching devices, is
able to control the reactive power drawn from the overhead line by each equipment. If the
conditions at each locomotive or train could be fed back to a central control point, it is possible
for a centrally located controller to calculate optimal values for the reactive power in each drive
and to send those commands back to the individual equipment.
In this thesis, AC railway power flows are optimised in real time and the results are used
to achieve some particular system objective via control of the PWM equipment as mobile
reactive power compensators. The system voltage profile and the total power losses can be
improved while the overall power factor at the feeder substation is also made nearer to unity.
For off-line simulation purposes, high execution speeds and low storage requirements
are not generally significant with the latest computer hardware. However, this real-time control
employs on-line optimising controllers, which need embedded power solvers running many
times faster than real time. Thus, a fast and efficient algorithm for AC railway power flow
calculation was developed. The proposed scheme is compared to a conventional reactive power
compensation, e.g. SVC, and found to be less expensive to implement.
Several test cases for AC electric railway systems are examined. The centralised area
control system leads to the best improvement where an existing fleet of diode or thyristor
phase-angle controlled locomotives is partially replaced with PWM ones, compared to that
obtained without compensation or to classical track-side Var compensation methods. From
these results, the potential for PWM locomotives to improve overall system performance is
confirmed.
This thesis is dedicated to my family, KULWORAWANICHPONG, and
the memory of my grand mother
ACKNOWLEDGEMENTS

I would like to thank my supervisor, Dr Colin GOODMAN, for his guidance, and invaluable
help and advice throughout the course of study and in writing this thesis.

I would like to acknowledge financial support from the Energy Policy and Planning Office,
Ministry of Energy, The Royal Thai Government, Thailand, and Suranaree University of
Technology, Thailand, during the period of study.

I am also grateful to Dr Sarawut SUJITJORN for his encouragement and sincere help for the
last ten years. Thanks are also extended to my colleges in the Power & Control Research
Group, The University of Birmingham, UK, for their help and interest in this work.

I am eternally grateful to my parents and my family for their continually sincere support.
Finally, I would like to express my gratitude to all whom I have failed to mention here, but have
generously supported me.
TABLE OF CONTENTS

Synopsis
Acknowledgements
List of illustrations
List of tables
List of abbreviations and symbols

Chapter 1 Introduction
1.1 Background 1
1.2 Aim of research and structure of thesis 2
1.3 Arrangement of chapters 4

Chapter 2 General Review
2.1 Introduction to mainline railway electrification 6
2.2 AC railway overhead catenary feeding system 7
2.3 Conventional power flow solution method 10
2.4 Computer-based modelling and simulation 12
2.5 Power system control and reactive power compensation 14
2.6 Summary 20

PART I
AC Railway Power Flow Calculation – Theory and Application

Chapter 3 AC Railway Power Flow Analysis
3.1 Introduction 23
3.2 Modelling of AC power feeding systems 24
3.3 Newton-Raphson AC railway power flow method 31
3.4 Sequential linear power flow method 42
3.5 Convergence, memory analysis and computer programming 46
3.6 Simulation results and discussion 54
3.7 Summary 66
PART II
AC Railway Power Flow Calculation – Exploitation of Sparsity

Chapter 4 Efficient algorithm for AC railway system simulation
4.1 Introduction 69
4.2 Methods of solving a linear system 69
4.3 Sparse linear system and solution method 73
4.4 Exploitation of sparsity for AC railway power system simulation 76
4.5 Simulation results 82
4.6 Summary 93

PART III
Optimal Area Control System

Chapter 5 Optimal AC railway power flow
5.1 Introduction to AC railway power flow problems 96
5.2 Practical use of the SVC in AC railway electrification 96
5.3 PWM locomotive as a mobile reactive power compensator 98
5.4 Optimal AC railway power flow problem and its solution 114
5.5 Simulation results and discussion 120
5.6 Summary 130

Chapter 6 Optimal area control simulation

6.1 Introduction
131
6.2 Area control simulation with discrete time step
131
6.3 Multi-train simulation
133
6.4 Power network solver and network capture
141
6.5 Simulation results and discussion
143
6.6 Summary
151
PART IV
Cost Estimation and Design

Chapter 7 Cost estimation for reactive power compensation
7.1 Introduction 153
7.2 Cost estimation of reactive power compensation for AC railways 154
7.3 Cost estimation of increasing MVA capacity of PWM locomotives 156
7.4 Design of the AC railway reactive power compensation 161
7.5 Summary 173

Chapter 8 Conclusions and future works
8.1 Summary of the PhD thesis 175
8.2 Conclusions 176
8.3 Suggestions to future work 178

References 182

Appendices

Appendix A Impedance and admittance matrices for a multi-conductor

system
A.1 Multi-conductor approach for AC railways A-1
A.2 Geometrical calculation of the impedance for an AT railway power
feeding system A-3
A.3 Autotransformer model A-5
A.4 Power substation model A-7
A.5 Train or locomotive model A-9

Appendix B Newton-Raphson method for solving non-linear equations
B.1 Newton-Raphson method B-1

Appendix C AC/DC power converter C-1
Appendix D Optimisation techniques
D.1 Overview D-1
D.2 Method of steepest descent D-2

Appendix E System data for simulation
E.1 Test systems for the single-phase AC railway power flow calculation E-1
E.2 Test systems for the bi-phase AC railway power flow calculation E-6
E.3 Double-track AT railway power feeding system (Fig. 4.17) E-7
E.4 Double-track AT railway power feeding system (Fig. 5.21) E-8
E.5 Double-track AT railway power feeding system (Fig. 5.21, Second test) E-9
E.6 Double-track AC railway power feeding system (Fig. 6.12) E-9
E.7 Double-track AC railway power feeding system (Section 7.4) E-10

Appendix F Numerical results
F.1 IEEE 24-bus test system F-1
F.2 IEEE 57-bus test system F-2

Appendix G Simulation Programs
Program structure and description G-1
Programming codes G-4

Appendix H Publication H-1
LIST OF ILLUSTRATIONS

Chapter 2
Fig. 2.1 Typical feeding diagram of a double-track 25 kV railway in UK 7
Fig. 2.2 Overhead catenary feeding systems for AC railways 8
Fig. 2.3 Typical bus representation 10
Fig. 2.4 A two-machine model for an AC transmission system 15
Fig. 2.5 Three basic compensation methods 16
Fig. 2.6 SVC and TCSC circuits 18
Fig. 2.7 SPS, STATCOM and DVC circuits 19
Fig. 2.8 HVDC and UPFC circuits 20

Chapter 3
Fig. 3.1 Single-phase AC railway power feeding model 24
Fig. 3.2 Power substation model 25
Fig. 3.3 Four locomotive models for power flow calculation 26
Fig. 3.4 Model representation of the AT feeding system 28
Fig. 3.5 Power substation model for the AT system 29
Fig. 3.6 Autotransformer modelFig. 3.7: Train model 29
Fig. 3.7 Train model 30
Fig. 3.8 Flow diagram of the NRPFM 50
Fig. 3.9 Flow diagram of the SLPFM 51
Fig. 3.10 Memory requirement of the NRPFM and SLPFM 53
Fig. 3.11 The modified standard IEEE 24-bus test system 54
Fig. 3.12 The modified standard IEEE 57-bus test system 55