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Failure-Modes Identification and Redundant Postfault Operation of Rotating Thyristor Rectifiers on Brushless Dual-Star Exciters
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Hydropower)ORCID iD: 0000-0002-3656-1032
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Hydropower)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Hydropower)
2018 (English)In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. PP, no 99, p. 1-10Article in journal (Refereed) Epub ahead of print
Abstract [en]

The excitation system plays a critical role in the operation of synchronous generators. An equipment failure could impact the voltage quality for smaller grids. Further, it can lead to cost penalties and reduced production for the power plant owner. Recently, a new high-speed-response rotating brushless exciter was developed that employs remote control of the rotating thyristors on the generator shaft. This has led to new possibilities for improving the performance of brushless exciters. This contribution investigates the failure modes of a dual-star outer pole exciter that feeds two separate thyristor bridges connected in parallel during normal operation. The possibility of redundant postfault operation due to open-thyristor or open-phase faults are demonstrated using experimental testing. The system is compared with the fault performance of a conventional three-phase system. This work includes the implementation and validation of a fault-predicting double d-q exciter model. In addition, the dangerous effects of a shorted-thyristor fault are investigated. A "skip firing" protection technique is briefly demonstrated for the fast isolation of such faults, yielding nondestructive postfault recovery and redundant failure-mode operation. The evidence shows that the dual-star exciter is a competitive choice for the future development of fault-tolerant brushless exciters.

Place, publisher, year, edition, pages
2018. Vol. PP, no 99, p. 1-10
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-317775DOI: 10.1109/TIE.2018.2833044OAI: oai:DiVA.org:uu-317775DiVA, id: diva2:1082788
Available from: 2017-03-17 Created: 2017-03-17 Last updated: 2018-05-04
In thesis
1. A New Paradigm for Large Brushless Hydrogenerators: Advantages Beyond the Static System
Open this publication in new window or tab >>A New Paradigm for Large Brushless Hydrogenerators: Advantages Beyond the Static System
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The grid code, FIKS, from the Norwegian transmission system operator (TSO), Statnett, states that synchronous generators > 25MVA, must have a static excitation system. However, an improved brushless excitation system is in operation on some commercial power plants (36MVA, 93.75rpm & 52MVA, 166.67rpm) with grid-assisting performance beyond the conventional static system. The convenional diode bridge is replaced with a remote-controlled thyristor bridge on the shaft. If wireless communication is not allowed, a control signal through brushes should be employed instead. The thesis explores the expected new era for large brushless hydrogenerators. The proposed brushless system have benefits of reduced regular maintenance due to elimination of brushes and reduced unscheduled maintenance due to redundancy; causing a redused cost-of-energy. A six-phase exciter design with a hybrid-mode thyristor bridge interface leads to improved fault-tolerance, better controllability, minimized torque pulsations and reduced armature currents of the exciter. Excitation boosting (EB) capability is included in the brushless system without additional components or circuitry, contrary to the static excitation system. The brushless excitation system is made insensitive to voltage dips in the interconnected grid, causing improved fault ride-through (FRT) capability and power system stabilizer (PSS) actions. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 93
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1491
Keyword
Brushless exciters, Rotating exciters, Permanent Magnet Machines, Synchronous Generator Excitation, Thyristor Rectifiers, Chopper Rectifiers
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-317780 (URN)978-91-554-9859-7 (ISBN)
Public defence
2017-05-10, Häggsalen, Ångströmlaboratoriet, Polacksbacken, Lägerhyddsvägen 2, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2017-04-19 Created: 2017-03-17 Last updated: 2018-02-15

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