Hybrid model predictive control techniques for safety factor profile and stored energy regulation while incorporating NBI constraints
B. Leard, S. T. Paruchuri, Z. Wang, T. Rafiq, E. Schuster
Nuclear Fusion 64 (2024) 086052 (15pp)
Abstract
|
|
A novel hybrid Model Predictive Control (MPC) algorithm has been designed for simultaneous
safety factor (q) profile and stored energy (w) control while incorporating the
pulse-width-modulation constraints associated with the neutral beam injection (NBI) system.
Regulation of the q-profile has been extensively shown to be a key factor for improved
confinement as well as non-inductive sustainment of the plasma current. Simultaneous control
of w is necessary to prevent the triggering of pressure-driven magnetohydrodynamic instabilities
as the controller shapes the q profile. Conventional MPC schemes proposed for q-profile control
have considered the NBI powers as continuous-time signals, ignoring the discrete-time nature of
these actuators and leading in some cases to performance loss. The hybrid MPC scheme in this
work has the capability of incorporating the discrete-time actuator dynamics as additional
constraints. In nonlinear simulations, the proposed hybrid MPC scheme demonstrates improved
q-profile+w control performance for NSTX-U operating scenarios.