A time-delay approach for the modeling and control of plasma instabilities in thermonuclear fusion

Emmanuel Witrant (1) , Erik Olofsson (2) , Silviu-Iulian Niculescu (3)

1 GIPSA-SLR - GIPSA - Systèmes linéaires et robustesse
2 Alvfèn lab
3 L2S - Laboratoire des signaux et systèmes

This letter presents a summary of [1], where we investigated the stability problems and control issues that occur in a reversedfield pinch (RFP) device, EXTRAP-T2R, used for research in fusion plasma physics and general plasma (ionized gas) dynamics. The plant exhibits, among other things, magnetohydrodynamic instabilities known as resistive-wall modes (RWMs), growing on a time-scale set by a surrounding non-perfectly conducting shell. We propose a new modeling approach that takes into account experimental constraints, such as the actuators dynamics and control latencies leading to a multivariable time-delay model of the system. The open-loop field-error characteristics are estimated and a stability analysis of the resulting closed-loop delay differential equation (DDE) emphasizes the importance of the delay effects. We then design an optimal PID controller (its structure being constrained by the intelligent-shell (IS) control architecture) that achieves a direct eigenvalue optimization of the corresponding DDE. The presented results are substantially based on and compared with experimental data.

Domaines: Physique des plasmas [physics.plasm-ph]; Automatique / Robotique

Emmanuel Witrant, Erik Olofsson, Silviu-Iulian Niculescu. A time-delay approach for the modeling and control of plasma instabilities in thermonuclear fusion. 2009. ⟨hal-00444540⟩