Simultaneous Optimal Regulation of Kinetic+Magnetic Scalar Plasma Properties for Robust Sustainment of Advanced Scenarios in NSTX-U
H. Al Khawaldeh, S.T. Paruchuri, Z. Wang, T. Rafiq, E. Schuster
29th IAEA Fusion Energy Conference
London, UK, October 16-21, 2023
Abstract
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A control algorithm based on real time optimization has been developed for the simultaneous regulation of kinetic and
magnetic scalar parameters in NSTX-U. This active control algorithm can contribute to operation optimization in tokamaks
by regulating advanced scenarios characterized by steady-state operation, stable plasma confinement, and high-performance
plasma. Actively shaping plasma profiles such as the safety factor is key in achieving and sustaining these advanced scenarios.
However, as the number of control objectives to be addressed simultaneously increases, the profile-control problem may need
to be reduced to the regulation of the profile at a few spatial locations due to controllability limits. In this case, the control
objectives are reduced to a finite number of scalar plasma parameters, such as plasma-profile values at specific spatial points
or volume-averaged plasma properties. On the positive side, effective simultaneous regulation of these scalar parameters may
be all what is needed to achieve a desired scenario. A model-based optimal-control algorithm for simultaneous regulation of
the central and boundary values of the safety-factor (q) profile, internal inductance (li), and normalized beta (βN ) has been
developed in this work. The control algorithm has been designed based on control-oriented state models for the poloidal
magnetic flux profile (ψ) and the plasma stored energy (W ) coupled with output models for q, li and βN . Moreover, in order to
demonstrate robustness against model uncertainties, the proposed control algorithm has been tested in higher-fidelity, nonlinear
simulations using COTSIM (Control Oriented Transport SIMulator).