First-Principles-Driven Model-Based Control of the Poloidal Magnetic Flux Profile at the DIII-D Tokamak
W. Wehner, W. Shi, E. Schuster, M.L. Walker, J.R. Ferron, T.C. Luce, D.A. Humphreys, R.D. Johnson and B.G. Penaflor
19th IFAC World Congress
Cape Town, South Africa, August 24-29, 2014
Abstract
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Efficient, high-gain operation of a tokamak device requires the
achievement of certain radial shapes for the toroidal current profile.
The evolution in time of the toroidal current profile in tokamaks is
related to the evolution of the poloidal magnetic flux profile. A
model-based control approach for the regulation of the poloidal
magnetic flux profile at the DIII-D tokamak is proposed in this work.
The model describing the poloidal flux evolution is based on a
control-oriented formulation of the magnetic diffusion equation.
Auxiliary heating and current drive (H&CD) systems including electron
cyclotron (EC) and neutral beam injection (NBI) along with the total
plasma current are used as actuators to manipulate the profile shape.
Optimal state feedback control with integral action is used to design
a controller to regulate the profile around a target while rejecting
disturbances. Combining the profile controller with control of the
plasma stored energy is found to improve tracking performance.
Simulations and experimental results are presented to demonstrate the
controllers effectiveness.