Predictive Control of the Rotation Profile using Neutral Beam Injection and Variable 3D Magnetic Fields
W.P. Wehner, M.D. Boyer, D.A. Humphreys, N.C. Logan, E. Schuster
Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)
Fort Lauderdale, FL, USA, October 21-25, 2019
Abstract
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Model predictive control (MPC) of the rotation profile using a
control-oriented momentum balance model which incorporates empirical
models of the NBI and 3D field torques has been developed for DIII-D.
Tokamak plasma rotation is widely recognized to significantly affect
the energy confinement, plasma stability, and access to high performance
operating scenarios. In this work, a generalized control capability
for aiding rotation-related physics studies is developed. To obtain a
control-oriented model, a simplified version of the momentum balance
equation is combined with empirical models of the momentum sources.
Recent progress in modeling the torque density profile driven by 3D
fields as a function of the non-axisymmetric field coil currents has
been embedded into the control design (N.C. Logan EPS 2018). MPC is
well suited to a variety of control objectives because it can explicitly
incorporate various types of constraints. For example, control of the
edge rotation to adjust the ELM suppression threshold while fixing the
stabilizing 𝑞=2 rotation. A simulation study is presented to demonstrate
the control performance and flexibility of the approach.