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2020 | Book

Introduction Read chapter Read first chapter

Protection Principle and Technology of the VSC-Based DC Grid

Authors: Prof. Bin Li, Jiawei He

Publisher: Springer Singapore

Book Series : Power Systems

Part of: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik"

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About this book

This book discusses key techniques of protection and fault ride-through in VSC-HVDC grids, including high-speed selective protection, DC fault current limitation, converter restarting, and DCCB reclosing strategies. It investigates how high-speed transient-variable-based protection can be used to improve grids’ acting sensitivity, acting reliability, and ability to withstand high transition resistance compared with traditional protection. In addition, it discusses the applicability of the pilot protections, including the current differential protection and travelign-wave based protection, in the dc grid, as well as the improved methods. Furthermore, it proposes several DC FCL topologies, which are suitable for DC grids. Lastly, in the context of overhead line application conditions, it explores converter restarting and DCCB reclosing strategies, which not only identify the fault property, but also limit the secondary damage to the system, improving the system’s operation security and reliability. As such, the book offers a comprehensive overview of original and advanced methods and techniques for the protection of VSC-HVDC grids.

Table of Contents

Frontmatter
Chapter 1. Introduction
Abstract
When the electric power was firstly applied, it was transferred based on the direct current. However, the early dc generator at the sending end and the dc motor at the receiving end are directly connected in series, so the reliability is very poor. In addition, it is difficult to transform the voltage in dc systems, and thus cannot realize the long-distance power transmission. At the end of the 19th century, the three-phase ac generator, induction motor and ac transformer were proposed successively.
Bin Li, Jiawei He
Chapter 2. Working Principle and Basic Control Strategy of the VSC-HVDC Grid
Abstract
In the VSC-HVDC grid, the converter is the core equipment for energy conversion and control between ac side and dc side. The voltage source converter (VSC) based on the full-controlled power electronic switches has varied topologies and control strategies. According to the used modulation principles, the VSC type mainly includes the PWM based VSC (two-level VSC and three-level VSC) and the modular multilevel converter (MMC).
Bin Li, Jiawei He
Chapter 3. DC Fault Characteristics of the VSC-HVDC System
Abstract
In the dc system, the two-level VSC is widely applied, in which the typical dc fault types mainly include the pole-to-pole fault and pole-to-ground fault.
Bin Li, Jiawei He
Chapter 4. High-Speed Single-Ended DC Line Protection for the VSC-HVDC Grid
Abstract
Compared with the line commutated converter (LCC) based HVDC transmission system, the dc fault propagation speed in the VSC-HVDC grid is much faster, which will damage the whole system in a few milliseconds.
Bin Li, Jiawei He
Chapter 5. High-Speed Differential Protection for the VSC-HVDC Grid
Abstract
In the LCC-HVDC transmission system, the dc current differential protection is generally used as the backup protection for the dc line. However, a long-time delay is introduced in the detailed differential criterion, to eliminate the negative influence of the unbalanced current mainly caused by the line distributed capacitor current, and guarantee the selectivity of the protection. It leads the operation time of the dc current differential protection to be hundreds-of-milliseconds level, which cannot satisfy the requirement of the VSC-based dc grid.
Bin Li, Jiawei He
Chapter 6. Traveling-Wave Based Direction Protection for the Multi-terminal HVDC Grid
Abstract
In the dc grid, the single-ended protection, which uses local signals to identify the fault line, is generally considered as the main protection for the dc transmission line, because the communication with the opposite end of the line is not required and the acting speed can be very fast.
Bin Li, Jiawei He
Chapter 7. DC Fault Current Limiting Technique Based on the H-bridge Topology
Abstract
According to the analysis in Chap. 3, the fault current increases extremely fast after dc fault [1]. For the operation security and power supply reliability, dc faults in the dc grid should be detected and interrupted with a high level of selectivity in several milliseconds, e.g., 2–4 ms [2, 3], resulting in the challenges for both the selective protection and fault isolation.
Bin Li, Jiawei He
Chapter 8. DC Fault Current Limiting Technique Based on the Current Commutation
Abstract
In order to avoid the negative influences of the directly installed dc reactor, Chap. 7 proposed to use H-bridge FCL and H-bridge SSCB, as shown in Fig. 8.1a, b, in the dc grid. As analyzed in Chap. 7, it can avoid the negative influences of the dc reactor on system normal operation and DCCB isolating speed. However, during normal operation, the load current will flow through series diodes and IGBTs in the H-bridge topology, thus leading to additional power loss.
Bin Li, Jiawei He
Chapter 9. Restart Control Strategy for the MMC-Based HVDC System
Abstract
The conventional MMC based on the half-bridge sub-module cannot handle the dc fault, due to the existence of the freewheeling diodes in the converter [1, 2]. Therefore, at present, most of the VSC-based dc transmission systems are based on the dc cables, to reduce the fault probability, such as the Zhoushan multi-terminal VSC-HVDC project in China [3].
Bin Li, Jiawei He
Chapter 10. The DCCB Reclosing Strategy in VSC-HVDC Grid
Abstract
In the VSC-HVDC system, the design of reclosing (or restarting) strategy is highly dependent on the used dc fault isolation method. At present, there are mainly two kinds of dc fault isolation methods feasible for flexible HVDC system, i.e., the self-eliminating converter technique and the DCCB technique. The self-eliminating converter technique has been introduced in Chap. 9, and the corresponding restart strategy has also been discussed. However, the future VSC-HVDC grid will be multi-terminal, where the dc lines interconnect with each other directly via the dc bus, such as the Zhangbei DC Grid Project which is under construction in China.
Bin Li, Jiawei He
Metadata
Title
Protection Principle and Technology of the VSC-Based DC Grid
Authors
Prof. Bin Li
Jiawei He
Copyright Year
2020
Publisher
Springer Singapore
Electronic ISBN
978-981-15-6644-8
Print ISBN
978-981-15-6643-1
DOI
https://doi.org/10.1007/978-981-15-6644-8