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Special Issue "Protection of Future Multi-Terminal HVDC Grids"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A: Electrical Engineering".

Deadline for manuscript submissions: closed (30 June 2021) | Viewed by 2695

Special Issue Editor

Prof. Dr. Athula D. Rajapakse
E-Mail Website
Guest Editor
Department of Electrical and Computer Engineering, University of Manitoba, Manitoba, Canada
Interests: power systems protection; power grids; distributed power generation; renewable energy; microgrids; fault diagnosis

Special Issue Information

Dear colleagues,

Multi-Terminal HVDC (MT-HVDC) grids are expected to play a key role in future electricity delivery systems. The main drivers for the development of MT-HVDC grids are the large-scale integration of renewable energy resources, particularly off-shore wind farms, and the promotion of international energy markets through the concept of super-grids. The voltage source converter (VSC) technology, practically implemented as modular multilevel converters (MMCs) based on half-bridge or full bridge submodules, enables the realization of MT-HVDC grids by offering flexibility to change the power flow direction and the possibility of connecting to weak AC systems. This Special Issue covers both MT-HVDC grids comprising more than two terminals and meshed DC paths and MT-HVDC systems comprising more than two terminals but no meshed DC paths. There are a few MMC based MT-HVDC systems in operation while the world’s first large-scale MT-HVDC grid, the Zhangbei four-terminal HVDC grid in China, is expected to be operational in 2022.

The protection of MT-HVDC grids is of utmost important to ensure the safety of equipment, preserve the stability of the AC grids they are connected to, and attain the full reliability benefits of MT-HVDC grids. The protection should prevent faults in an AC system that result in the loss of generation or load in a MT-HVDC grid, impacting the other AC systems via the MT-HVDC grid. Similarly, a fault inside a converter station should not result in complete shutdown of a MT-HVDC grid. The faults on the DC side lines, cables, or busbars are the most challenging, as all converters contribute to the fault current, causing a sudden reduction in the voltage of DC buses, severely restricting the power flow, and risking the shutdown of the entire HVDC grid. DC side fault currents can rise very rapidly, peaking well above the steady state fault current due to discharge of converter capacitance and stored energy in inductive and capacitive elements in the fault current paths. A DC side fault is reflected on the AC side as a three-phase short circuit, and a MMC based on half-bridge submodules is unable to block the steady state fault current contribution from the AC side. On the other hand, limitations of the DC circuit breaker technology, both technical and economic, make the problem even more challenging. Therefore, the protection of MT-HVDC grids has recently become a subject of intense research.

This Special Issue of Energies aims to discuss the challenges and solutions to the problem of the protection of future MT-HVDC grids. The topics of interest include, but are not limited to

  • Fault detection and discrimination techniques for MT-HVDC grids;
  • Identification of faults inside converter stations;
  • Developments in DC circuit breaker technology and practical testing;
  • Fast and sensitive protection techniques for submarine cables and mixed transmission system with both cables and overhead lines;
  • Impacts of different grid configurations and grounding schemes on fault discrimination and protection;
  • Fault current limiters and their impacts on the protection of MT-HVDC grids;
  • Impact of fault tolerant converters on the protection of MT-HVDC grids;
  • Co-ordinating strategies for fault handling;
  • Temporary fault clearing strategies;
  • Methodologies for specifying MT-HVDC grid protection requirements and testing;
  • Analytical models for fault current characterization and fault location.

Prof. Dr. Athula D. Rajapakse
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • DC Fault Clearing in HVDC Grids
  • Multi-terminal HVDC Grids
  • Protection of HVDC Grids
  • DC Fault Detection and Discrimination
  • HVDC Circuit Breakers
  • HVDC Fault Current Limiters
  • HVDC Grid Fault Analysis
  • Fault Tolerant Converters
  • HVDC Grid Grounding
  • DC Cable Protection

Published Papers (3 papers)

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Research

Article
Circuit Breaker Failure Protection Strategy for HVDC Grids
Energies 2021, 14(14), 4326; https://doi.org/10.3390/en14144326 - 18 Jul 2021
Cited by 1 | Viewed by 641
Abstract
HVDC grids demand the fast and reliable operation of the protection system. The failure of any protection element should initialize a backup protection almost immediately in order to assure the system’s stability. This paper proposes a novel backup strategy that covers the failure [...] Read more.
HVDC grids demand the fast and reliable operation of the protection system. The failure of any protection element should initialize a backup protection almost immediately in order to assure the system’s stability. This paper proposes a novel backup strategy that covers the failure of the primary protection including the malfunctioning of the HVDC circuit breaker. Only local voltage measurements are employed in the proposed backup protection and the voltage derivative is calculated at both sides of the limiting inductor. Consequently, the speed and reliability of the protection system are enhanced, since no communication channel is needed. This paper contains a thorough specification of the proposed protection strategy. This strategy is validated in a four-terminal HVDC grid with various fault case scenarios, including high-resistance fault cases. The operation of the backup protection is reliable and remarkably fast. Full article
(This article belongs to the Special Issue Protection of Future Multi-Terminal HVDC Grids)
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Article
Design and Performance Analysis of a Saturated Iron-Core Superconducting Fault Current Limiter for DC Power Systems
Energies 2020, 13(22), 6090; https://doi.org/10.3390/en13226090 - 20 Nov 2020
Cited by 8 | Viewed by 872
Abstract
A saturated iron-core superconducting fault current limiter (SI-SFCL) can significantly limit the magnitude of the fault current and reduce the stress on circuit breakers in direct current (DC) power systems. The SI-SFCL consists of three main parts: one magnetic iron-core, one normal conductive [...] Read more.
A saturated iron-core superconducting fault current limiter (SI-SFCL) can significantly limit the magnitude of the fault current and reduce the stress on circuit breakers in direct current (DC) power systems. The SI-SFCL consists of three main parts: one magnetic iron-core, one normal conductive primary coil (CPC), and one superconducting secondary coil (SSC). This paper deals with the design options for the coil system of the SI-SFCL and confirms their operating characteristics through a physical experiment. The electromagnetic characteristics and operational features of the SI-SFCL was analyzed by a 3D finite element method simulation model. The design of the SSC was based on shape, wire types, required fault current limit and protection aspects. In the CPC, the bobbin was designed based on material selection, cost, structural design, and the effects of the SI-SFCL on the fault current limit. Based on these simulation results, a laboratory-scale SI-SFCL was developed, specifically fabricated to operate on a 500 V, 50 A direct current (DC) power system. In the experiment, the operating characteristics of each coil were analyzed, and the fault current limit of the SI-SFCL according to the operating currents of the SSC and bobbin design of the CPC were confirmed. Finally, the cost analysis of the SI-SFCL with the proposed design options of the coil system was implemented. The results obtained through this study can be effectively used to large-scale SI-SFCL development studies for high-voltage direct current (HVDC) power systems. Full article
(This article belongs to the Special Issue Protection of Future Multi-Terminal HVDC Grids)
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Article
A Selective Fault Clearing Scheme for a Hybrid VSC-LCC Multi-Terminal HVdc System
Energies 2020, 13(14), 3554; https://doi.org/10.3390/en13143554 - 10 Jul 2020
Cited by 1 | Viewed by 763
Abstract
A selective fault clearing scheme is proposed for a hybrid voltage source converter (VSC)-line commutated converter (LCC) multi-terminal high voltage direct current (HVdc) transmission structure in which two small capacity VSC stations tap into the main transmission line of a high capacity LCC-HVdc [...] Read more.
A selective fault clearing scheme is proposed for a hybrid voltage source converter (VSC)-line commutated converter (LCC) multi-terminal high voltage direct current (HVdc) transmission structure in which two small capacity VSC stations tap into the main transmission line of a high capacity LCC-HVdc link. The use of dc circuit breakers (dc CBs) on the branches connecting to VSCs at the tapping points is explored to minimize the impact of tapping on the reliability of the main LCC link. This arrangement allows clearing of temporary faults on the main LCC line as usual by force retardation of the LCC rectifier. The faults on the branches connecting to VSC stations can be cleared by blocking insulated gate bipolar transistors (IGBTs) and opening ac circuit breakers (ac CB), without affecting the main line’s performance. A local voltage and current measurement based fault discrimination scheme is developed to identify the faulted sections and pole(s), and trigger appropriate fault recovery functions. This fault discrimination scheme is capable of detecting and discriminating short circuits and high resistances faults in any branch well before 2 ms. For the test grid considered, 6 kA, 2 ms dc CBs can easily facilitate the intended fault clearing functions and maintain the power transfer through healthy pole during single-pole faults. Full article
(This article belongs to the Special Issue Protection of Future Multi-Terminal HVDC Grids)
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