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Transient stability of rotary frequency converter fed low frequency railway grids: The Impact of Different Grid Impedances and Different Converter Station Configurations
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
2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

One method of strengthening low frequency AC railway grids is to upgrade Booster Transformer (BT) catenary systems, to Auto Transformer (AT) catenary systems. An AT catenary system has lower equivalent impedance compared to a BT system. Thus, an upgrade makes the existing converter stations electrically closer.

Converter stations may have different types of Rotary Frequency Converters (RFCs) installed in them, and it is not well explored how different RFCs behaves and interact during and after a large disturbance.

Using the Anderson-Fouad model of synchronous machines to describe the dynamics of RFCs, several case studies have been performed through numerical simulations. The studies investigate the interactions within and between converter stations constituted with different RFC types, for BT as well AT catenary systems.

The numerical studies reveal that replacing BT with AT catenary systems, results in a more oscillatory system behaviour. This is seen for example in the power oscillations between and inside converter stations, after fault clearance.

Place, publisher, year, edition, pages
American Society of Mechanical Engineers (ASME) , 2018. article id UNSP V001T09A006
Series
Proceedings of the ASME Joint Rail Conference, ISSN 1559-9531, E-ISSN 2160-1380
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-70235DOI: 10.1115/JRC2018-6247ISI: 000438662100091Scopus ID: 2-s2.0-85050882038ISBN: 978-0-7918-5097-8 (electronic)OAI: oai:DiVA.org:ltu-70235DiVA, id: diva2:1236979
Conference
ASME Joint Rail Conference (JRC 2018), Pittsburgh, PA, APR 18-20, 2018
Available from: 2018-08-07 Created: 2018-08-07 Last updated: 2021-03-22Bibliographically 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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