Integrated Control of Individual Plasma Scalars with Simultaneous NTM Suppression
A. Pajares, E. Schuster, K.E. Thome, A.S. Welander, J.L. Barr, N.W. Eidietis, D.A. Humphreys
Nuclear Fusion 62 (2022) 036018 (22pp).
Abstract
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A novel integrated-control architecture has been tested in nonlinear,
one-dimensional simulations using the control-oriented transport simulator
(COTSIM) and in DIII-D experiments. Integrated architectures that can
perform continuous-mission control while also handling off-normal events
will be vital in future reactor-grade tokamaks. Continuous-mission
controllers for individual magnetic and kinetic scalars (thermal
stored-energy, volume-average toroidal rotation, and safety
factor profile at different spatial locations) have been integrated
in this work with event-triggered neoclassical tearing-mode (NTM)
suppression controllers by combining them into an architecture augmented
by a supervisory and exception handling (S&EH) system and an actuator
management (AM) system. The AM system, which enables the integration of
competing controllers, solves in real time a nonlinear optimization
problem that takes into account the high-level control priorities dictated
by the S&EH system. The resulting architecture offers a high level of
integration and some of the functionalities that will be required to
fulfill the advanced-control requirements anticipated for ITER. Initial
simulations using COTSIM suggest that the plasma performance and its MHD
stability may be improved under integrated feedback control. In addition,
the integrated-control architecture has been implemented in the DIII-D
plasma control system and tested experimentally for the first time ever
in DIII-D in a high-qmin scenario, which is a candidate for steady-state
operation in ITER.