TRANSP-based Closed-loop Simulations of Current Profile Optimal Regulation in NSTX-Upgrade
Z.O. Ilhan, M.D. Boyer, E. Schuster
Fusion Engineering and Design, 146 (2019) 555–558.
Abstract
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Active control of the toroidal current density profile is critical for
the upgraded National Spherical Torus eXperiment device (NSTX-U) to
maintain operation at the desired high-performance, MHD-stable, plasma
regime. Initial efforts towards current density profile control have
led to the development of a control-oriented, physics-based, plasma-response
model, which combines the magnetic diffusion equation with empirical
correlations for the kinetic profiles and the non-inductive current
sources. The developed control-oriented model has been successfully
tailored to the NSTX-U geometry and actuators. Moreover, a series of
efforts have been made towards the design of model-based controllers,
including a linear-quadratic-integral optimal control strategy that
can regulate the current density profile around a prescribed target
profile while rejecting disturbances. In this work, the tracking
performance of the proposed current-profile optimal controller is
tested in numerical simu- lations based on the physics-oriented code
TRANSP. These high-fidelity closed-loop simulations, which are a
critical step before experimental implementation and testing, are
enabled by a flexible framework recently developed to perform feedback
control design and simulation in TRANSP.