The traction power supply system plays a critical role in enabling rapid development of high-speed and heavy-haul railways. However, the conventional systems face serious challenges including neutral section passing, power quality, and limited overload capacity. The advanced co-phase traction power supply system based on power electronics established an interconnected traction network across multiple substations. This system eliminates neutral section, reduces substation capacity requirements and voltage drops, and significantly improves power supply efficiency. It also enhances grid stability by enabling mutual backup support between substations during faults. Additionally, it mitigates traditional power quality issues, including three-phase voltage unbalance, inadequate reactive power compensation, and harmonic distortions.
The advanced co-phase traction power supply system is highly suitable for next-generation high-speed railway and compatible with upgrades to existing traction networks. It also offers an innovative solution for specialized projects such as longdistance traction power supply, weak-grid high-altitude railways, and new energy grid connection. Consequently, it represents an ideal next-generation traction power supply technology. However, realizing this system urgently requires fundamental research on its core component—power electronic converters. Their topologies, operation principles, modulation schemes, and control strategies must be thoroughly analyzed and validated prior to engineering implementation to mitigate technical risks. This book will provide a detailed discussion centered on the aforementioned topics. It is divided into seven chapters:
Chapter 1: Introduction
Chapter 2: Grid-Connected Characteristic Analysis of Advanced Co-phase Traction Power Supply System
Chapter 3: Control and Modulation of Grid-Connected Three-Phase Converter
Chapter 4: Control and Modulation of Single-Phase Converter in Traction Power Supply
Chapter 5: Diode-Clamped Multilevel Three-Phase-to-Single-Phase Converter
Chapter 6: Modular Multilevel Three-Phase-to-Single-Phase Converter
Chapter 7: Analysis and Control of Two-Phase-to-Single-Phase ConverterThe author of this book, Professor Zeliang Shu, has participated in the development and implementation of next-generation traction supply system, including the world’s first Meishan co-phase power supply system in 2007, heavy-haul railways in Shanxi, and urban lines in Wenzhou. In 2011, he led three projects funded by the National Natural Science Foundation of China (NSFC) on converters and control strategies for ideal co-phase traction systems, three-phase-to-single-phase converters, and two-phase-to-single-phase power electronic transformers of advanced co-phase traction power supply system. This book constitutes a comprehensive summary of these research efforts. It has been made possible through the invaluable support of the following individuals, to whom I extend my deepest gratitude: Prof. Qunzan Li, Prof. Shaofeng Xie, Prof. Xiaoqiong He, Siyang Liu, Biao Yu, Li Zhao, Feng Chu, Han Yan, Yousong Zhou, Linghui Meng, Xufeng Zhang, Yajun Chen, Xiaodong Yin, Ziwei Zhang, Song, Shitao Wang, Jiangling Nie, Jingci Wu, Jiangpeng Yang, Shun Wang, Yuhao Deng, and others.
Owing to the inherent constraints of this work, certain omissions and inaccuracies may persist. We welcome constructive feedback and corrections from readers.
Chengdu, Sichuan, China
August 2025
Zeliang Shu
Table of Contents
1 Introduction 1
1.1 Brief Introduction to Electrification Development in Railway Transport Field 1
1.1.1 Development of Electrified Railway and High-Speed Railway 1
1.1.2 Overview of Electrified Railway Development in China 2
1.2 Brief Introduction to Research and Application of Traction Power Supply System 4
1.2.1 Overview of Traction Power Supply Technology Abroad 4
1.2.2 Overview of Traction Power Supply System in China 6
1.2.3 Existing Improvement Solutions for Traction Power Supply System 7
1.2.4 Characteristics of Ideal Traction Power Supply Systems 9
1.3 Overview of Research and Application of Co-phase Traction Power Supply 9
1.4 Overview of Research on Advanced Co-phase Traction Power Supply 11
1.5 Balance Principles for Common Types of Traction Transformers 13
1.6 Converter Topology in Advanced Co-phase Traction Power Supply System 15
1.6.1 Three-Phase-to-Single-Phase Converter Topology 16
1.6.2 Two-Phase-to-Single-Phase Converter Topology 17
1.6.3 Single-Phase-to-Single-Phase Converter Topology 18
1.6.4 Multilevel Conversion Circuit Topology 19
1.7 Summary 21
References 21
2 Grid-Connected Characteristic Analysis of Advanced Co-phase Traction Power Supply System 25
2.1 Overview 25
2.1.1 Basic Architecture of Advanced Co-phase Traction Power Supply System 25
2.1.2 Influence of Traction Network Impedance on Substation Output Voltage 28
2.1.3 Analysis of Impedance Characteristics of Traction Network 28
2.1.4 Influence of Traction Network Impedance on Converter Output Voltage 29
2.1.5 Analysis of Voltage Step-Down of Continuous Traction Network 33
2.2 Current Distribution Characteristics of Traction Network with Interconnected Substations 34
2.2.1 Analysis of Output Current Difference Between Substations Connected to Grid and Network 34
2.2.2 Automatic Current Distribution Characteristics Between Substations 35
2.3 Control Strategy of Interconnection for Continuous Feeding 39
2.3.1 Droop Control Analysis of Parallel Converters 40
2.3.2 Analysis of Droop Characteristics of Continuous Power Supply System 42
2.3.3 Improved Interconnection Control Strategy Based on Droop Characteristics 44
2.3.4 Simulation and Analysis of System with Interconnected Two Substations 49
2.3.5 Simulation and Analysis of System with Interconnected Three Substations 55
2.4 Summary 61
References 62
3 Control and Modulation of Grid-Connected Three-Phase Converter 65
3.1 Three-Phase Converter and Circuit Analysis 65
3.1.1 Three-Phase Two-Level Converter 66
3.1.2 Three-Phase Three-Level Converter 70
3.1.3 T-Type Three-Level Converter 75
3.1.4 Three-Phase Cascade Converter 78
3.2 Active and Reactive Decoupling Control of Three-Phase Interconnection Converter 81
3.2.1 Model of Three-Phase Converter in Two-Phase Static Coordinate System 81
3.2.2 Active and Reactive Decoupling Control in DQ Coordinate System 83
3.2.3 Analysis of Current Four-Quadrant Characteristics for Interconnection Converter 85
3.3 Analysis of Three-Phase Phase-Locked Loop 88
3.3.1 Basic Principle and Structure of Three-Phase Phase-Locked Loop 89
3.3.2 Influence of Voltage Distortion on Phase-Locked Loop 91
3.3.3 Simulation and Design of Three-Phase Phase-Locked Loop 94
3.4 Three-Phase SVPWM 97
3.4.1 Reference Vector Calculation and Sector Determination 98
3.4.2 Vector Decomposition of Reference Voltage and Dwell Duration Calculation 99
3.4.3 A Fast SVPWM Algorithm and Expansion in Multilevel Scenarios 101
3.4.4 FPGA Design and Implementation for Fast SVPWM Algorithm 105
3.5 Simulation and Experiment of Three-Phase Converter 109
3.6 Summary 114
References 115
4 Control and Modulation of Single-Phase Converter in Traction Power Supply 117
