Accessibility and Reproducibility of Stable High-qmin Steady-State Scenarios by q-profile+βN Model Predictive Control
E. Schuster, W. Wehner, C.T. Holcomb, B. Victor, J.R. Ferron and T.C. Luce
Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)
San Jose, CA, USA, October 31 - November 4, 2016
Abstract
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The capability of combined q-profile and βN control to enable access
to and repeatability of steady-state scenarios for qmin>1.4
discharges has been assessed in DIII-D experiments. To steer the
plasma to the de- sired state, model predictive control (MPC) of both
the q-profile and βN numerically solves successive optimization
problems in real time over a receding time horizon by exploiting
efficient quadratic programming techniques. A key advantage of this
control approach is that it allows for explicit incorporation of
state/input constraints to prevent the controller from driving the
plasma outside of stability/performance limits and obtain, as closely
as possible, steady state conditions. The enabler of this
feedback-control approach is a control-oriented model capturing the
dominant physics of the q-profile and βN responses to the available
actuators. Experiments suggest that control-oriented model-based
scenario planning in combination with MPC can play a crucial role in
exploring stability limits of scenarios of interest.