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Fast-response rotating brushless exciters for improved stability of synchronous generators
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Hydro Power)
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The Norwegian Network Code FIKS from the Norwegian Transmission System Operator (TSO) Statnett, states that synchronous generators ≥ 25 MVA must have a static excitation system. It also includes requirements on the step time response and the available field winding ceiling voltage of the excitation system. An improved brushless excitation system is in operation in some pilot power plants. A rotating thyristor bridge is controlled via Bluetooth. The step time response is as fast as conventional static excitation systems. However, a ceiling voltage factor of 2 requires the thyristor bridge to operate at firing angles about 60 degrees. High torque pulsations, low power factor and low utilization of the exciter is the end result. New power electronic interfaces on the shaft results in a betterutilization of the designed exciter and improves the mechanical performance as well as the controllability of the generator field winding. Permanent magnet rotating exciters increase the field forcing strength of the synchronous generator, yielding improved transient stability (Fault Ride-Through req.). Brushless exciters also reduces regular maintenance of the generator. The thesis includes experiments on a state of the art synchronous generator test setup including constructed PM exciter and different power electronic solutions. Some investigations has been done on industrial power plants as well.

Place, publisher, year, edition, pages
Uppsala: Institutionen för teknikvetenskaper , 2016.
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; 347-16L
Keyword [en]
synchronous generators, permanent magnet machines, excitation systems, power electronic interfaces
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-292835OAI: oai:DiVA.org:uu-292835DiVA: diva2:926767
Presentation
2016-06-13, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2016-07-07 Created: 2016-05-09 Last updated: 2016-07-07Bibliographically approved
List of papers
1. Comparison of Thyristor-Controlled Rectification Topologies for a Six-Phase Rotating Brushless Permanent Magnet Exciter
Open this publication in new window or tab >>Comparison of Thyristor-Controlled Rectification Topologies for a Six-Phase Rotating Brushless Permanent Magnet Exciter
2016 (English)In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 31, no 1, 314-322 p.Article in journal (Refereed) Published
Abstract [en]

The thyristor bridge rectifier has proven to be a reliable solution regarding control of excitation equipment for synchronous generators. However, in rotating brushless exciters, the diode rectifier is the dominant topology on the shaft. In order to improve the step response of rotating exciters, one could put a thyristor bridge rectifier on the rotating part and control the firing angle remotely from a stationary controller. This paper compares different multiphase configurations of permanent magnet synchronous machines as a rotating exciter and discusses the possibility to reduce the torque ripple by selecting the appropriate rectification topology. The paper also explains the implications of the self and mutual inductances of the armature windings for the performance of the exciter.

Keyword
brushless exciters, rotating exciters, controlled excitation, permanent magnet machines, synchronous generators, voltage stabiliy
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-269214 (URN)10.1109/TEC.2015.2480884 (DOI)000372024100030 ()
Available from: 2015-12-15 Created: 2015-12-15 Last updated: 2017-12-01Bibliographically approved
2. Step time response evaluation of different synchronous generator excitation systems
Open this publication in new window or tab >>Step time response evaluation of different synchronous generator excitation systems
2016 (English)In: Step time response evaluation of different synchronous generator excitation systems, IEEE Xplore, 2016Conference paper, Published paper (Refereed)
Abstract [en]

A fast step response of an excitation system is critical for a synchronous generator in order to maintain stability under disturbances in the interconnected power grid. This is the main reason that the static excitation system has been preferred for large synchronous generators. Some transmission system operators even have requirements that the excitation system should be static for synchronous generators above a certain size. The requirement is set in order to fulfill a certain goal for the step time response. As technology progresses forward, the static excitation system will not any longer be the only option for a fast controllable excitation system. New brushless rotating excitation systems, with wireless control interfaces, can be even faster than the static excitation system. They also reduce the need of maintenance of the synchronous generator. With permanent magnet exciters, the excitation system can be independent from the grid, maintaining the excitation response under voltage dips in the power grid. This paper evaluates the dynamic performance of the static excitation system compared with different types of brushless rotating excitation systems.

Place, publisher, year, edition, pages
IEEE Xplore: , 2016
Keyword
synchronous generator modelling
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-292792 (URN)10.1109/ENERGYCON.2016.7513956 (DOI)000390822900086 ()9781467384636 (ISBN)
Conference
IEEE International Energy Conference 2016 (ENERGYCON'16)
Available from: 2016-05-09 Created: 2016-05-09 Last updated: 2017-03-17Bibliographically approved
3. Design and characterization of a rotating brushless PM exciter for a synchronous generator test setup
Open this publication in new window or tab >>Design and characterization of a rotating brushless PM exciter for a synchronous generator test setup
Show others...
2016 (English)In: Design and characterization of a rotating brushless PM exciter for a synchronous generator test setup / [ed] IEEE Xplore, 2016, 259-265 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper deals with the characterization and construction of a rotating brushless PM exciter intended for synchronous generator excitation purposes. Traditionally, PM exciters are used as pre-exciters in synchronous generator excitations systems. In order to reduce the number of components and to increase the step time response of the system, a PM exciter is designed as an outer pole PM machine, with permanent magnets on the stator and armature windings on the rotor. The exciter was constructed electrically and mechanically to be fitted into an in-house synchronous generator test setup. A finite element model of the exciter was validated with no-load measurements of voltages and magnetic flux densities. The exciter was then characterized with unsaturated and saturated parameters.

Keyword
Brushless exciters, rotating exciters, permanent magnet machines, machine design, voltage measurement
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-292798 (URN)10.1109/ICELMACH.2016.7732536 (DOI)000390884900037 ()9781509025381 (ISBN)
Conference
International Conference on Electrical Machines 2016 (ICEM'16), Lausanne, SWITZERLAND, SEP 04-07, 2016
Available from: 2016-05-09 Created: 2016-05-09 Last updated: 2017-11-20Bibliographically approved
4. Evaluation of different power electronic interfaces for control of a rotating brushless PM exciter
Open this publication in new window or tab >>Evaluation of different power electronic interfaces for control of a rotating brushless PM exciter
Show others...
2016 (English)In: Evaluation of different power electronic interfaces for control of a rotating brushless PM exciter / [ed] IEEE Xplore, 2016Conference paper, Published paper (Refereed)
Abstract [en]

This paper investigates the performance of different power electronic interfaces for a rotating brushless permanent magnet exciter, designed for a synchronous generator test setup. A passive rotating diode bridge is commonly used as the rotating interface in conventional brushless excitation systems. Those systems are known to be slow dynamically, since they cannot control the generator field voltage directly. Including active switching components on the rotating shaft, like thyristors or transistors, brushless excitation systems can be comparable to static excitation systems. Brushless excitation systems has the benefit of less regular maintenance. With permanent magnets on the stator of the designed exciter, the excitation system improves its field forcing capability. Results show that modern power electronic interfaces utilize the exciter machine optimally, increase the power factor, reduce the torque pulsations, maintain the available field winding ceiling voltage and improve the field winding controllability.

Keyword
power electronic interfaces
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-292801 (URN)10.1109/IECON.2016.7794011 (DOI)978-1-5090-3474-1 (ISBN)
Conference
Annual Conference on of the IEEE Industrial Electronics Society 2016 (IECON'16)
Available from: 2016-05-09 Created: 2016-05-09 Last updated: 2017-03-17

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