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Model predictive control of resistive wall modes in the reversed-field pinch
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The reversed-field pinch (RFP) is a magnetic confinement fusion (MCF) device. It exhibits a variety of unstable modes that can be explained by magnetohydrodynamic (MHD) theory. A particular unstable mode that is treated in this work is the resistive wall mode (RWM), which occurs when the shell of the device has finite conductivity. Application of control engineering tools appears to be important for the operation of the RFP. A model-based control approach is pursued to stabilize the RWM. The approach consists of experimental modeling of RWM using a class of system identification techniques. The obtained model is then used as a basis for Mode Predictive Control (MPC) design. The MPC employs the model to build predictions of the system and find a control input that optimizes the predicted behavior of the system. It is shown that the formulation of the MPC allows the user to incorporate several physics relevant phenomena aside from RWMs. The results are encouraging for MPC to be a useful tool for future MCF operation.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , v, 38 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2015:027
National Category
Fusion, Plasma and Space Physics Control Engineering
Identifiers
URN: urn:nbn:se:kth:diva-168617ISBN: 978-91-7595-596-4 (print)OAI: oai:DiVA.org:kth-168617DiVA: diva2:817533
Presentation
2015-06-12, Alfvénlab seminarierum (1419), Teknikringen 31, KTH, Stockholm, 13:15 (English)
Opponent
Supervisors
Note

QC 20150605

Available from: 2015-06-05 Created: 2015-06-05 Last updated: 2015-06-05Bibliographically approved
List of papers
1. Implementation of model predictive control for resistive wall mode stabilization on EXTRAP T2R
Open this publication in new window or tab >>Implementation of model predictive control for resistive wall mode stabilization on EXTRAP T2R
2015 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 57, no 10, 104005Article in journal (Refereed) Published
Abstract [en]

A model predictive control (MPC) method for stabilization of the resistive wall mode (RWM) in the EXTRAP T2R reversed-field pinch is presented. The system identification technique is used to obtain a linearized empirical model of EXTRAP T2R. MPC employs the model for prediction and computes optimal control inputs that satisfy performance criterion. The use of a linearized form of the model allows for compact formulation of MPC, implemented on a millisecond timescale, that can be used for real-time control. The design allows the user to arbitrarily suppress any selected Fourier mode. The experimental results from EXTRAP T2R show that the designed and implemented MPC successfully stabilizes the RWM.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-168631 (URN)10.1088/0741-3335/57/10/104005 (DOI)000366679100006 ()2-s2.0-84940854105 (Scopus ID)
Note

Updated from manuscript to article.

QC 20151127

Available from: 2015-06-05 Created: 2015-06-05 Last updated: 2017-12-04Bibliographically approved
2. Design and operation of fast model predictive controller for stabilization of magnetohydrodynamic mode in a fusion device
Open this publication in new window or tab >>Design and operation of fast model predictive controller for stabilization of magnetohydrodynamic mode in a fusion device
(English)Manuscript (preprint) (Other academic)
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-168632 (URN)
Note

QS 2015

Available from: 2015-06-05 Created: 2015-06-05 Last updated: 2015-06-05Bibliographically approved
3. A method for the estimate of the wall diffusion for non-axisymmetric fields using rotating external fields
Open this publication in new window or tab >>A method for the estimate of the wall diffusion for non-axisymmetric fields using rotating external fields
Show others...
2013 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 55, no 8, 084001- p.Article in journal (Refereed) Published
Abstract [en]

A new method for the estimate of the wall diffusion time of non-axisymmetric fields is developed. The method based on rotating external fields and on the measurement of the wall frequency response is developed and tested in EXTRAP T2R. The method allows the experimental estimate of the wall diffusion time for each Fourier harmonic and the estimate of the wall diffusion toroidal asymmetries. The method intrinsically considers the effects of three-dimensional structures and of the shell gaps. Far from the gaps, experimental results are in good agreement with the diffusion time estimated with a simple cylindrical model that assumes a homogeneous wall. The method is also applied with non-standard configurations of the coil array, in order to mimic tokamak-relevant settings with a partial wall coverage and active coils of large toroidal extent. The comparison with the full coverage results shows good agreement if the effects of the relevant sidebands are considered.

Keyword
Resistive-Wall, Feedback Stabilization, Active Control, DIII-D, Modes, Pinch, Device
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-127495 (URN)10.1088/0741-3335/55/8/084001 (DOI)000322702700002 ()2-s2.0-84881511440 (Scopus ID)
Conference
17th Annual Workshop on Magnetohydrodynamic (MHD) Stability Control - Addressing the Disruption Challenge for ITER, NOV 05-07, 2012, New York, NY
Note

QC 20130902

Available from: 2013-09-02 Created: 2013-08-30 Last updated: 2017-12-06Bibliographically approved
4. Resistive Wall Mode Studies utilizing External Magnetic Perturbations
Open this publication in new window or tab >>Resistive Wall Mode Studies utilizing External Magnetic Perturbations
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-168633 (URN)
Note

QS 2015

Available from: 2015-06-05 Created: 2015-06-05 Last updated: 2015-06-05Bibliographically approved

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