Extremum-Seeking-Based Receding-Horizon Optimal Control of Plasma
Current Profile at the DIII-D Tokamak
Y. Ou, C. Xu, E. Schuster, T. C. Luce, J. R. Ferron, M. L. Walker and D. A. Humphreys
IFAC World Congress on Automatic Control
Seoul, Korea, July 6-11, 2008
Abstract
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A key goal in the control of a magnetic fusion reactor is to maintain
current profiles that are compatible with a high fraction of
self-generated non-inductive current as well as with
magnetohydrodynamic (MHD) stability at high plasma pressure. This
enables high fusion gain and noninductive sustainment of plasma
current for steady-state operation. The approach taken toward
establishing such plasma current profiles at the DIII-D tokamak is to
create the desired profile during the plasma current ramp-up and early
flattop phases. The evolution in time of the current profile is
related to the evolution of the poloidal flux, which is modeled in
normalized cylindrical coordinates using a nonlinear partial
differential equation (PDE) usually referred to as the magnetic
diffusion equation. We propose, and test in simulations, an
extremum-seeking-based, receding-horizon, diffusivity-interior-boundary
control scheme designed to match as close as possible a desired current
profile within a prespecified time interval.