Simultaneous Boundary and Distributed Feedback Control of the Current Profile in H-mode Discharges on DIII-D
M.D. Boyer, J. Barton, W. Shi, W. Wehner, E. Schuster, J.R. Ferron, M.L. Walker, D.A. Humphreys, F. Turco, T.C. Luce, R.D. Johnson and B.G. Penaflor
19th IFAC World Congress
Cape Town, South Africa, August 24-29, 2014
Abstract
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Control of the current profile in tokamak plasmas has been shown to
play an important role in achieving advanced scenarios that could
enable steady-state operation. The nonlinearity and spatially
distributed nature of the current profile dynamics motivate the use of
model-based control designs. In this work, we consider a
control-oriented model of the current profile evolution in DIII-D
high-confinement (H-mode) discharges, and the problem of regulating
the current profile around a desired trajectory. The PDE model is
discretized in space with a finite difference method and a
backstepping design is applied to obtain a transformation from the
original system into a particular target system with desirable
properties. The resulting boundary condition control law is
complemented with control laws for the available distributed actuators.
The combined control strategy uses nonlinear combinations of the total
plasma current, total power, and line averaged density as actuators.
Simulation and experimental results show the ability of the controller
to track desired targets and to reject input disturbances.