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Impact of Reduced Share of Rotary Frequency Converters in a Low Frequency Synchronous Railway Grid: A Transient Stability Study
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.ORCID iD: 0000-0003-2109-060X
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.ORCID iD: 0000-0003-4074-9529
2019 (English)In: 2019 Joint Rail Conference, ASME Press, 2019, article id V001T09A002Conference paper, Published paper (Other academic)
Abstract [en]

Most low-frequency AC single-phase railway grids have both power-electronic based Static Frequency Converters (SFCs) and electrical-machine based Rotary Frequency Converters (RFCs) connecting them to the three-phase public grid.

Already today, in some such grids, a majority of the power conversion is from SFCs. As railway traffic (and thus power demand) increases, more SFCs are installed for capacity increase, while the number of RFCs remains (almost) constant. Thus, the share of SFCs is expected to increase, and the ratio of installed rotational inertia over installed power to decrease.

This paper investigates how different shares of SFCs affect the transient stability of low-frequency AC railway grids when having a mix of RFCs and SFCs converting three-phase AC power to single-phase AC power. Results from numerical simulations of the interactions that occur between converters when and after the grid is subject to a fault are presented.

The numerical studies show that with an increased share of SFCs there is an increased oscillatory behavior, for example in the voltage magnitude and active power after fault clearance.

Place, publisher, year, edition, pages
ASME Press, 2019. article id V001T09A002
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-71798DOI: 10.1115/JRC2019-1238Scopus ID: 2-s2.0-85083952903OAI: oai:DiVA.org:ltu-71798DiVA, id: diva2:1266645
Conference
ASME/IEEE Joint Rail Conference, 9-12 April, 2019, Snowbird, Utah, USA
Note

ISBN för värdpublikation: 978-0-7918-5852-3

Available from: 2018-11-28 Created: 2018-11-28 Last updated: 2020-05-11Bibliographically approved
In thesis
1. Stability of Low-Frequency AC Railways: Models and Transient Stability
Open this publication in new window or tab >>Stability of Low-Frequency AC Railways: Models and Transient Stability
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Low-frequency AC railway grids are unique in the sense that a only few countries around the world uses them, still however, they are an important parts of their countries infrastructures. Due to the usage of a dierent frequency than the public grid of the country, conversion of frequency is needed for the interconnection. The frequency conversion is done by machine based rotary frequency converters or power electronic based static frequency converters.

When reinforcing with new power conversion capacity, mostly static frequency converters are installed since rotary frequency converters for railways have not been manufactured for some time. As more static frequency converterare introduced, the share of rotary frequency converters is reduced. It is not well explored how the stability of low-frequency AC railways is affected with a large share of static frequency converters.

In this thesis, the main goal has been to obtain knowledge of the stability of low-frequency AC railway grids, with focus on synchronous ones. The electromechanical stability of a synchronous low-frequency AC railway is explored through numerical simulations, where the transient stability is the main focus.

The main contributions of this thesis is proposing a model of a rotary frequency converter, proposing a model of a static frequency converter, and transient stability simulations. The model of the rotary frequency converter uses established machine models, whereas the static frequency converter model has been developed with help of measurements. It can be concluded that the proposed static frequency converter model captures the main behaviour of the measurements of a static frequency converter.

The transient stability of synchronous AC railway grids is studied, through numerical simulations. The studied cases are for instance dierent railway grid congurations with dierent types rotary frequency converters and railway grids with mixes of static frequency converters and static frequency converter.

The main conclusion is that the rotary frequency converter fed synchronous railway grids studied are transiently stable, and the studied railway grids where rotary frequency converters are gradually replaced with static frequency converter are also transiently stable. However, it was found that the studied railway grids obtain a heavier oscillatory behaviour when there is a mix of rotary frequency converters and static frequency converters.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-71795 (URN)978-91-7790-292-8 (ISBN)978-91-7790-293-5 (ISBN)
Public defence
2019-02-28, Skellefteå, 10:00 (English)
Opponent
Supervisors
Available from: 2018-12-27 Created: 2018-12-13 Last updated: 2019-02-14Bibliographically approved

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Laury, JohnAbrahamsson, LarsBollen, Math

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