Development of a Robust Current Profile Feedback Controller in DIII-D

Y. Ou, E. Schuster, T. C. Luce, J. R. Ferron, M. L. Walker and D. A. Humphreys, T.A. Casper, W.H. Meyer

Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)

Atlanta, Georgia, November 2-6, 2009

Abstract

Setting up a suitable current profile has been demonstrated to be a key condition for one candidate advanced tokamak scenario with improved confinement and steady-state operation. A control-oriented model of the current pro- file evolution in DIII-D was recently developed for the plasma current ramp-up and early-flattop phases [1] and used to synthesize open-loop control schemes tested both in simulations and experiments [2]. A robust closed-loop controller is proposed to regulate the current profile under the presence of model uncertainties in the plasma resistivity. Using the POD/Galerkin technique, the control-oriented PDE model is reformulated into a low-dimensional ODE model that preserves the dominant dynamics, and an H∞ controller is designed to minimize the regulation/tracking error. A Corsica-based simulation assessment is presented.

[1] Y. Ou, et al., Fusion Engin. Design 82 (2007) 1153.
[2] Y. Ou, et al., Plasma Phys. Control. Fusion 50 (2008) 115001.