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Comparison of Thyristor Rectifier Configurations for a Six-Phase Rotating Brushless Outer Pole PM Exciter
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)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Hydropower)
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(English)In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948Article in journal (Refereed) Epub ahead of print
Abstract [en]

Recent technological developments have caused a renewed interest in the brushless excitation system. With the application of wireless communication, the conventional diode bridge has been replaced with fully controllable thyristors on the shaft. It offers the same dynamic performance as the conventional static excitation system. The thyristor bridge of the conventional three- phase exciter needs to be controlled with a high firing angle in normal operation in order to fulfill a requirement of both a high ceiling voltage and a high ceiling current. A high firing angle causes high torque ripple to be absorbed by the exciter stator and a low power factor results in a low utilization of the designed exciter. In this contribution we present a strategy that solves this problem by looking into combinations of thyristor configurations of a double- star six-phase connection of the exciter. Experimental results are used to verify the circuit models implemented for this investigation. A hybrid-mode 12-pulse thyristor bridge configuration seems to be a good solution for implementations in commercial apparatus. An additional switch interconnects two separate thyristor bridges from parallel- to series-connection at the rectifier output, and utilizes the advantages of both topologies.

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-317774DOI: 10.1109.TIE.2017.2726963OAI: oai:DiVA.org:uu-317774DiVA: diva2:1082786
Available from: 2017-03-17 Created: 2017-03-17 Last updated: 2017-07-16
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. 93 p.
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: 2017-04-19

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