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

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.