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Closed-loop control and identification of resistive shell magnetohydrodynamics for the reversed-field pinch
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

It is demonstrated that control software updates for the magnetic confinement fusion experiment EXTRAP T2R can enable novel studies of plasma physics. Specifically, it is shown that the boundary radial magnetic field in T2R can be maintained at finite levels by feedback. System identification methods to measure in situ magnetohydrodynamic stability are developed and applied with encouraging results. Subsequently, results from closed-loop identification are used for retooling the T2R regulator. The track of research here pursued could possibly be relevant for future thermonuclear fusion reactors.

Place, publisher, year, edition, pages
2010. , 78 p.
Series
Trita-EE, ISSN 1653-5146 ; 2010:019
National Category
Fusion, Plasma and Space Physics Control Engineering
Identifiers
URN: urn:nbn:se:kth:diva-12794ISBN: 978-91-7415-644-7 (print)OAI: oai:DiVA.org:kth-12794DiVA: diva2:318856
Presentation
2010-05-26, E1, KTH, Lindstedtsvägen 3, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100518Available from: 2010-05-18 Created: 2010-05-11 Last updated: 2012-03-21Bibliographically approved
List of papers
1. Closed-loop direct parametric identification of magnetohydrodynamic normal modes spectra in EXTRAP-T2R reversed-field pinch
Open this publication in new window or tab >>Closed-loop direct parametric identification of magnetohydrodynamic normal modes spectra in EXTRAP-T2R reversed-field pinch
2009 (English)In: 2009 IEEE CONTROL APPLICATIONS CCA & INTELLIGENT CONTROL, 2009, 1449-1454 p.Conference paper, Published paper (Refereed)
Abstract [en]

The reversed-field pinch (RFP) EXTRAP-T2R (T2R) is a plasma physics experiment with particular relevance for magnetic confinement fusion (MCF) research. T2R is very well equipped for investigations of magnetohydrodynamic (MHD) instabilities known as resistive-wall modes (RWMs), growing on a time-scale set by a surrounding non-perfectly conducting shell. The RWM instability is also subject of intense research in tokamak experiments (another MCF configuration). Recently, multiple RWMs have been stabilized in T2R using arrays of active (current-carrying) and sensor (voltage-measuring) coils equidistributed on the shell. In this paper, the MHD normal modes dynamics is probed in the required feedback operation by simultaneously, and pseudo-randomly, exciting the spectrum in the spatial sense. Spectra are then extracted by prediction-error minimization based on an observer that tracks dynamically aliased modes and the results thus obtained are related, and compared, to established linear MHD stability theory. This pioneer study at T2R is, arguably, appealling both to plasma physicists and automatic control staff.

Series
IEEE International Conference on Control Applications, ISSN 1085-1992
Keyword
RESISTIVE WALL MODES, FEEDBACK-CONTROL, TOKAMAK PLASMA, STABILIZATION, SHELL
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-25561 (URN)000279628300245 ()2-s2.0-74049145778 (Scopus ID)978-1-4244-4601-8 (ISBN)
Conference
IEEE International Conference on Control Applications/International Symposium on Intelligent Control St Petersburg, RUSSIA, JUL 08-10, 2009
Note
QC 20110216Available from: 2010-11-18 Created: 2010-10-27 Last updated: 2011-02-16Bibliographically approved
2. Vector dither experiment design and direct parametric identification of reversed-field pinch normal modes
Open this publication in new window or tab >>Vector dither experiment design and direct parametric identification of reversed-field pinch normal modes
Show others...
2009 (English)In: Proceedings of the IEEE Conference on Decision and Control, 2009, 1348-1353 p.Conference paper, Published paper (Refereed)
Abstract [en]

Magnetic confinement fusion (MCF) research ambitiously endeavours to develop a major future energy source. MCF power plant designs, typically some variation on the tokamak, unfortunately suffer from magnetohydrodynamic (MHD) instabilities. One unstable mode is known as the resistive-wall mode (RWM) which is a macroscopically global type of perturbation that can degrade or even terminate the plasma in the reactor if not stabilized. In this work the topic of RWMs is studied for the reversed-field pinch (RFP), another toroidal MCF concept, similar to the tokamak. The problem of identifying RWM dynamics during closed-loop operation is tackled by letting physics-based parametric modeling join forces with convex programming experiment design. An established MHD normal modes description is assessed for the RFP by synthesizing a multivariable dither signal where spatial fourier modes are spectrally shaped, with regard to real experiment constraints, to yield minimum variance parameter estimates in the prediction-error framework. The dithering is applied to the real RFP plant EXTRAP-T2R, and experimental MHD spectra are obtained by an automated procedure.

Keyword
Automated procedures, Closed-loop operation, Convex programming, Dither signals, Energy source, Experiment design, Fourier modes
National Category
Control Engineering
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-12889 (URN)10.1109/CDC.2009.5400016 (DOI)000336893601138 ()2-s2.0-77950843926 (Scopus ID)978-142443871-6 (ISBN)
Conference
48th IEEE Conference on Decision and Control held jointly with 2009 28th Chinese Control Conference, CDC/CCC 2009, Shanghai, 15-18 December, 2009
Funder
Swedish Research Council, 621-2005-4345
Note

QC 20100518

Available from: 2010-05-18 Created: 2010-05-18 Last updated: 2015-06-10Bibliographically approved
3. Controlled magnetohydrodynamic mode sustainment in the reversed-field pinch: Theory, design and experiments
Open this publication in new window or tab >>Controlled magnetohydrodynamic mode sustainment in the reversed-field pinch: Theory, design and experiments
2009 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 84, no 7-11, 1455-1459 p.Article in journal (Refereed) Published
Abstract [en]

A novel control system design for magnetohydrodynamic (MHD) resistive-wall mode (RWM) stabilization is developed from the viewpoint of process control. The engineering approach assumed consists of system identification, selection of feedback interconnections, and subsequently, associated feedback gain tuning. A design for general output tracking is devised, implemented and experimentally verified to be capable of sustaining MHD modes in the reversed-field pinch (RFP) machine EXTRAP-T2R. In principle, by active feedback. the plasma column boundary is forced to 'user-specified' helicities of prescribed amplitudes and phases. Experimental success is mainly attributed to careful identification of local magnetic field diffusion time-constants, and individual actuator channel peripheral dynamics. Addition of functionality and key features of this new MHD feedback system software might provide a versatile tool for experimental plasma dynamics and innovative MHD stability research.

Keyword
Fusion plasma physics, Magnetohydrodynamics, Resistive-wall modes, Automatic control, System identification, Process control, INTELLIGENT SHELL, FEEDBACK, STABILIZATION
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-12891 (URN)10.1016/j.fusengdes.2008.11.052 (DOI)000268012700078 ()2-s2.0-67349189891 (Scopus ID)
Note
QC 20100518Available from: 2010-05-18 Created: 2010-05-18 Last updated: 2017-12-12Bibliographically approved
4. Synthesis and operation of an FFT-decouped fixed-order RFP plasma control system based on identification data
Open this publication in new window or tab >>Synthesis and operation of an FFT-decouped fixed-order RFP plasma control system based on identification data
(English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:kth:diva-12893 (URN)
Note
QC 20100518Available from: 2010-05-18 Created: 2010-05-18 Last updated: 2017-12-12Bibliographically approved

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Citation style
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