Transient Stability in Low Frequency Railways with Mixed Electronic and Rotational Generation
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Transient stability concerns the ability of a power system to maintain synchronism after a large disturbance. Transient stability plays an important role in guaranteeing operational security and reliability and has been extensively studies for large 50 Hz and 60 Hz transmission systems. However, transient stability of low frequency railway grids has not been properly investigated.As low frequency railway grids operate at another frequency than the public grid, conversion of frequency is needed. This conversion is performed by Rotary Frequency Converters or by Static Frequency Converters. These two types of converters have a different impact on stability. In this thesis, the overall aim is to obtain knowledge on transient stability in low frequency railway grids, with focus on the Swedish synchronous-synchronous railway grid with a mix of Rotary and Static Frequency Converters.The transient stability problem is approached by developing a simplified model of a Static Frequency Converter that can be used for the stability studies in low frequency railways. The Static Frequency Converter is modelled as single phase generator with an equivalent inertia and damping. However as Static Frequency converters cannot handle currents much above their ratings, current limitation is implemented. The current limitation is needed to avoid unnecessary tripping of the converter during fault or other high current situations. With the model developed for a Static Frequency Converter and with a simplified model of a Rotary Frequency Converter, transient stability studies have been performed for several test systems representing the Swedish railway grid.The simulations performed shows the appearance of power oscillations after a large disturbance, between a Static Frequency Converter and a Rotary Frequency Converter when these are operating in parallel. The simulations also showed that the systems studied were stable for realistic values of the fault-clearing time.
Place, publisher, year, edition, pages
Luleå tekniska universitet, 2016.
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Research subject Electric Power Engineering
IdentifiersURN: urn:nbn:se:ltu:diva-26485Local ID: e7ab9979-b027-4d1a-b26d-46e673ed1e06ISBN: 978-91-7583-632-4ISBN: 978-91-7583-633-1 (PDF)OAI: oai:DiVA.org:ltu-26485DiVA: diva2:999647
Godkänd; 2016; 20160510 (johlau); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: John Laury Ämne: Elkraftteknik/Electric Power Engineering Uppsats: Transient Stability in Low Frequency Railways with Mixed Electronic and Rotational Generation Examinator: Professor Math Bollen, Institutionen för teknikvetenskap och matematik, Avdelning: Energiteknik, Luleå tekniska universitet. Diskutant: Docent Thorsten Schütte, STRI AB, Västerås Tid: Fredag 17 juni, 2016 kl 10.00 Plats: Skellefteå, Luleå tekniska universitet2016-09-302016-09-30Bibliographically approved