First-Principles-Driven Model-Based Optimal Control of the Current Profile in NSTX-U
Z. Ilhan, J. Barton, W. Wehner, E. Schuster, D. Gates, S. Gerhardt, E. Kolemen and J. Menard
Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)
New Orleans, Lousiana, USA, October 27-31, 2014
Abstract
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Regulation in time of the toroidal current profile is one of the main
challenges toward the realization of the next-step operational goals
for NSTX-U. A nonlinear, control-oriented, physics-based model
describing the temporal evolution of the current profile is obtained
by combining the magnetic diffusion equation with empirical
correlations obtained at NSTX-U for the electron density, electron
temperature, and non-inductive current drives. In this work, the
proposed model is embedded into the control design process to
synthesize a time-variant, linear-quadratic-integral, optimal
controller capable of regulating the safety factor profile around a
desired target profile while rejecting disturbances. Neutral beam
injectors and the total plasma current are used as actuators to shape
the current profile. The effectiveness of the proposed controller in
regulating the safety factor profile in NSTX-U is demonstrated via
closed-loop predictive simulations carried out in PTRANSP.