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Implementation of model predictive control for resistive wall mode stabilization on EXTRAP T2R
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.ORCID iD: 0000-0002-5259-0458
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.ORCID iD: 0000-0002-9546-4494
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. Vol. 57, no 10, 104005
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-168631DOI: 10.1088/0741-3335/57/10/104005ISI: 000366679100006Scopus ID: 2-s2.0-84940854105OAI: oai:DiVA.org:kth-168631DiVA: diva2:817582
Note

Updated from manuscript to article.

QC 20151127

Available from: 2015-06-05 Created: 2015-06-05 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Model predictive control of resistive wall modes in the reversed-field pinch
Open this publication in new window or tab >>Model predictive control of resistive wall modes in the reversed-field pinch
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:nbn:se:kth:diva-168617 (URN)978-91-7595-596-4 (ISBN)
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
2. Model based approach to resistive wall magnetohydrodynamic instability control: Experimental modeling and optimal control for the reversed-field pinch
Open this publication in new window or tab >>Model based approach to resistive wall magnetohydrodynamic instability control: Experimental modeling and optimal control for the reversed-field pinch
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The primary objective of fusion research is to realize a thermonuclear fusion power plant. The main method to confine the hot plasma is by using a magnetic field. The reversed-field pinch is a type of magnetic confinement device which suffers from variety of magnetohy- drodynamic (MHD) instabilities. A particular unstable mode that is treated in this work is the resistive wall mode (RWM), which occurs due to the current gradient in the RFP and has growth rates of the order of the magnetic diffusion time of the wall. Application of control engineering tools appears to allow a robust and stable RFP operation.A model-based approach to stabilize the RWMs is pursued in this thesis. The approach consists of empirical modeling of RWMs using a class of subspace identification methodology. The obtained model is then used as a basis for a model based controller. In particular the first experimental results of using a predictive control for RWM stabilization are obtained. It is shown that the formulation of the model based controller allows the user to incorporate several physics relevant phenomena along with the stabilization of RWM. Another use of the model is shown to estimate and compensate the inherent error field. The results are encouraging, and the methods appear to be generically useful as research tools in controlled magnetic confinement fusion.

Abstract [sv]

Fusionsforskningens primära mål är att förverkliga en ny typ av kraftverk baserade på termonukleär fusion. Den viktigaste metoden för att innesluta det heta plasmat är användandet av  magnetfält. ”Reverserat-fält pinch” (RFP) är en typ av anläggning för magnetisk inneslutning av fusionsplasma som uppvisar ett flertal magneto-hydrodynamiska instabiliteter. En specifik instabil mod som behandlas i detta arbete är”resistiv-vägg” moden (RWM). Den orsakas av strömgradienten i RFPn och tillväxer med en tidskonstant som är av samma storleksordning som magnetfältets diffusionstid i det omgivande metallskalet.  Tillämpning av verktyg från reglerteknikområdet förefaller tillåta en robust och stabil RFP drift. I detta arbete används ett modell-baserat tillvägagångssätt för kompensering av RWM. Det innefattar empirisk modellering av RWM med användning av ”subspace” system-identifieringsmetoder. Den erhållna modellen används sedan som grund för en modell-baserad regulator. De första experimentella resultaten från modell-prediktiv kompensering av RWM har erhållits.  I detta arbete har också visats att formuleringen av den modellbaserade regulatorn tillåter användaren att integrera flera relevanta fysikaliska aspekter förutom RWM. Ytterligare en användning av modellen är för att göra uppskattning och kompensering av avvikelser i anläggningens magnetfält, så kallade fält-fel. Resultaten är uppmuntrande, och det förefaller som om de undersökta metoderna är allmänt användbara som verktyg för forskning om magnetisk inneslutning av fusionsplasma.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 59 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2016:192
Keyword
magnetohydrodynamic, model based control, reversed-field pinch
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-200817 (URN)978-91-7729-228-9 (ISBN)
Public defence
2017-02-09, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Supervisors
Note

QC 20170202

Available from: 2017-02-02 Created: 2017-02-02 Last updated: 2017-02-02Bibliographically approved

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Brunsell, PerFrassinetti, Lorenzo

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