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

Boyer, Mark D.; André, R.; Gates, D.; Gerhardt, S. P.; Ménard, J.; Poli, F. M.

doi:10.1088/1741-4326/aa68e9

Cited by 10 publications

(12 citation statements)

References 39 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%

“…maintaining specified gaps between the plasma and PFCs) and for establishing plasma stability and evolution. For example, in [31,35], simulations with the integrated modeling code TRANSP showed that modifying the plasma shaping can be used as a virtual actuator to actively control the current profile in NSTX-U by affecting bootstrap current and beam current drive profiles.…”

Section: Plasma Shape Control System Roles and Requirementsmentioning

confidence: 99%

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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%

Section: Plasma Shape Control System Roles and Requirementsmentioning

confidence: 99%

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

et al. 2018

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“…Expert files are external coding that are linked to the main executable and that allow users to manipulate the simulations by including additional features. A direct application of expert files is for simulations dedicated to develop control algorithms and it has been applied on NSTX-U for control of the plasma performance [14,15] and of plasma rotation [16] with Neutral Beam Injection. In this respect expert files can provide valuable inputs for control requirements, diagnostic sensitivity or development of actuator power sharing control algorithms, because they allow the study of the plasma response to external perturbations in the presence of high-fidelity physics models.…”

Section: Calculation Of Ntm Stability In Transp With Simulated Ec Fementioning

confidence: 99%

Electron cyclotron power management for control of neoclassical tearing modes in the ITER baseline scenario

et al. 2017

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Time-dependent simulations are used to evolve plasma discharges in combination with a modified Rutherford equation for calculation of neoclassical tearing mode (NTM) stability in response to electron cyclotron (EC) feedback control in ITER. The main application of this integrated approach is to support the development of control algorithms by analyzing the plasma response with physics-based models and to assess how uncertainties in the detection of the magnetic island and in the EC alignment affect the ability of the ITER EC system to fulfill its purpose. Simulations indicate that it is critical to detect the island as soon as possible, before its size exceeds the EC deposition width, and that maintaining alignment with the rational surface within half of the EC deposition width is needed for stabilization and suppression of the modes, especially in the case of modes with helicity (2, 1). A broadening of the deposition profile, for example due to wave scattering by turbulence fluctuations or not well aligned beams, could even be favorable in the case of the (2, 1)−NTM, by relaxing an over-focussing of the EC beam and improving the stabilization at the mode onset. Pre-emptive control reduces the power needed for suppression and stabilization in the ITER baseline discharge to a maximum of 5 MW, which should be reserved and available to the upper launcher during the entire flattop phase. Assuming continuous triggering of NTMs, with preemptive control ITER would be still able to demonstrate a fusion gain of Q = 10.

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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%

“…The beam slowing down time and the energy confinement time (each on the order of 10-100 ms) tend to smooth the effect of the modulations. The beam modulation scheme was simulated in closed loop TRANSP simulations of NSTX-U in [35] where small oscillations in stored energy were observed since the energy confinement time and minimum on/off times were close in that case. However, the controller performance was not significantly impacted by these oscillations.…”

Section: Actuators Measurements and Disturbancesmentioning

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

Cited by 10 publications

References 39 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

Electron cyclotron power management for control of neoclassical tearing modes in the ITER baseline scenario

Model predictive control of KSTAR equilibrium parameters enabled by TRANSP

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