Simultaneous feedback control of plasma rotation and stored energy on NSTX-U using neoclassical toroidal viscosity and neutral beam injection

Goumiri, Imène; Rowley, Clarence W.; Sabbagh, S.A.; Gates, D.; Boyer, Mark D.; Gerhardt, S. P.; Kolemen, Egemen; Ménard, J.

doi:10.1063/1.4976853

Cited by 16 publications

(8 citation statements)

References 42 publications

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“…Furthermore, much progress has been made on the development of new algorithms for advanced control applications (e.g. [31][32][33][34][35]), including current and rotation profile, snowflake divertor control, and power/particle exhaust handling.…”

Section: Plasma Boundary Shape Control and Realtime Equilibrium Recon...mentioning

confidence: 99%

Plasma boundary shape control and real-time equilibrium reconstruction on NSTX-U

et al. 2018

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The upgrade to the National Spherical Torus eXperiment (NSTX-U) included two main improvements: a larger center-stack, enabling higher toroidal field and longer pulse duration, and the addition of three new tangentially aimed neutral beam sources, which increase available heating and current drive, and allow for flexibility in shaping power, torque, current, and particle deposition profiles. To best use these new capabilities and meet the high-performance operational goals of NSTX-U, major upgrades to the NSTX-U control system (NCS) hardware and software have been made. Several control algorithms, including those used for real-time equilibrium reconstruction and shape control, have been upgraded to improve and extend plasma control capabilities. As part of the commissioning phase of first plasma operations, the shape control system was tuned to control the boundary in both inner-wall limited and diverted discharges. It has been used to accurately track the requested evolution of the boundary (including the size of the inner gap between the plasma and central solenoid, which is a challenge for the ST configuration), X-point locations, and strike point locations, enabling repeatable discharge evolutions for scenario development and diagnostic commissioning.

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Section: Plasma Boundary Shape Control and Realtime Equilibrium Recon...mentioning

confidence: 99%

Plasma boundary shape control and real-time equilibrium reconstruction on NSTX-U

et al. 2018

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“…While earlier efforts to implement feedback control in TRANSP relied on injecting custom run-specific FORTRAN code into TRANSP runs [15,26,[34][35][36], the new approach enables any external code to control plasma parameters during a TRANSP run through a socket connection interface. This added flexibility reduces the development time for testing control algorithms and will enable software-in-the-loop testing of plasma control algorithms.…”

Section: Closed Loop Control Simulation Frameworkmentioning

confidence: 99%

Model predictive control of KSTAR equilibrium parameters enabled by TRANSP

Boyer¹,

Yuan²,

Ahn³

et al. 2020

Nucl. Fusion

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Due to the complex behavior of tokamak plasmas and the importance of optimizing performance while avoiding instabilities and machine limits, plasma control algorithms are becoming increasingly dependent on sophisticated model-based control approaches. It is anticipated that the use of integrated modeling codes in the model-based control design process will reduce the amount of experimental time needed to implement new control algorithms by facilitating development of control-oriented models and enabling higher-fidelity closed-loop simulations. In this work, a reduced model is developed from a series of TRANSP simulations and is used to develop a model predictive control (MPC) algorithm for controlling important equilibrium parameters in KSTAR [] discharges. The control algorithm uses the KSTAR neutral beam injection system and the target plasma current and plasma boundary as actuators, and optimizes the plasma stored energy, loop voltage, and internal inductance while avoiding constraints that could lead to disruptions. Higher fidelity testing of the control algorithm is performed using a flexible framework for enabling external processes to actively control plasma parameters in TRANSP simulations. Closed-loop simulations demonstrate the ability of the control algorithm to respond to disturbances in density and confinement, handle actuator failures, and move the discharge to high non-inductive fraction conditions.

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“…Its predictive mode has been used for scenario development on NSTX-U to explore the potential equilibrium operating space of the device, including fully noninductive scenarios [29], and has been used to explore noninductive plasma current ramp up [30]. Recently, the ability to include feedback control algorithms in TRANSP simulations has been developed to study control algorithms for stored energy and plasma profiles in inductive scenarios [21][22][23]. The framework for feedback simulations in TRANSP uses the NUBEAM [31] module for calculating neutral beam heating and current drive, and the ISOLVER free-boundary equilibrium solver [32,33] to evolve the discharge shape and current distribution.…”

Section: Predictive Simulation Approachmentioning

confidence: 99%

“…Ongoing development (e.g. [21][22][23]) aims to enable current and rotation profile control, power and particle exhaust control, and edge transport barrier control, building on the successful advances made during NSTX operations [24][25][26]. This paper extends this development by examining potential approaches to active real-time control during noninductive scenarios using a framework for feedback control simulations in the integrated modeling code TRANSP [21].…”

Section: Introductionmentioning

confidence: 99%

Feedback control design for non-inductively sustained scenarios in NSTX-U using TRANSP

et al. 2017

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This paper examines a method for real-time control of non-inductively sustained scenarios in NSTX-U by using TRANSP, a time-dependent integrated modeling code for prediction and interpretive analysis of tokamak experimental data, as a simulator. The actuators considered for control in this work are the six neutral beam sources and the plasma boundary shape. To understand the response of the plasma current, stored energy, and central safety factor to these actuators and to enable systematic design of control algorithms, simulations were run in which the actuators were modulated and a linearized dynamic response model was generated. A multi-variable model-based control scheme that accounts for the coupling and slow dynamics of the system while mitigating the effect of actuator limitations was designed and simulated. Simulations show that modest changes in the outer gap and heating power can improve the response time of the system, reject perturbations, and track target values of the controlled values.

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Simultaneous feedback control of plasma rotation and stored energy on NSTX-U using neoclassical toroidal viscosity and neutral beam injection

Cited by 16 publications

References 42 publications

Plasma boundary shape control and real-time equilibrium reconstruction on NSTX-U

Plasma boundary shape control and real-time equilibrium reconstruction on NSTX-U

Model predictive control of KSTAR equilibrium parameters enabled by TRANSP

Feedback control design for non-inductively sustained scenarios in NSTX-U using TRANSP

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