Abstract
Plasma control systems (PCS) in tokamaks need to fulfill a number of control tasks to achieve the desired physics goals. In present-day devices, actuators are usually assigned to a single control task. However, in future tokamaks, only a limited set of actuators is available for multiple control tasks at the same time. The priority to perform specific control tasks may change in real-time due to unforeseen plasma events and actuator availability may change due to failure. This requires the real-time allocation of available actuators to realize the requests by the control tasks, also known as actuator management.In this paper, we analyze possible architectures to interface the control tasks with the allocation of actuators inside the PCS. Additionally, we present an efficient actuator allocation algorithm for Heating and Current Drive (H&CD) actuators. The actuator allocation problem is formulated as a Mixed-Integer Quadratic Programming optimization problem, allowing to quickly search for the best allocation option without the need to compute all allocation options. The algorithms performance is demonstrated in examples involving the full proposed ITER H&CD system, where the desired allocation behavior is successfully achieved. This work contributes to establishing integrated control routines with shared actuators on existing and future tokamaks.
Highlights
Tokamaks require a plasma control system (PCS) to control plasma quantities of interest, in order to ensure that physics goals are met while remaining within operational and machine limits
In present-day devices, actuators are usually assigned to a single control task for an entire experiment, e.g. to density control, plasma beta control or the control of Neoclassical Tearing Modes (NTMs)
It should be stressed that we do not perform a closed-loop simulation including all PCS components and a plant simulator
Summary
Tokamaks require a plasma control system (PCS) to control plasma quantities of interest, in order to ensure that physics goals are met while remaining within operational and machine limits. An actuator allocation algorithm was developed and successfully implemented for the ECRH system at ASDEX Upgrade [14,15] This algorithm computes in real-time for all possible allocation options the benefits (are control task requests achieved) minus the costs (required movements of launchers, etc.), while taking actuator availability into account. This is an excellent first demonstration of real-time actuator management. Examples involving the full planned ITER H&CD system size, including Neutral Beam Injection (NBI), Ion Cyclotron (IC) and EC H&CD systems, demonstrate the algorithm's capability to perform the actuator allocation in real-time in correspondence to the desired allocation behavior.
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