Speaker
Pavel Korenev
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1079.pdf
Robust plasma position, current, and shape control system
simulated on plasma evolution code for the spherical tokamak Globus-M
Y.V. Mitrishkin1,2, A.A. Prokhorov,1,2, P.S. Korenev1,2, M.I. Patrov3
1
Lomonosov Moscow State University, Faculty of Physics, Moscow, Russia
2
V.A. Trapeznikov Inst. of Control Sciences, Russian Academy of Sciences, Moscow, Russia
3
Ioffe Physical-Technical Inst. of the Russian Academy of Sciences, Saint Petersburg, Russia
To simulate plasma shape and position during tokamak discharges a new plasma evolution code
was developed in MATLAB. To obtain plasma position and coil currents the plasma motion
equation, Faraday’s law equations for PF coils, vacuum vessel and plasma circuits are
numerically solved with input voltages. Forces acting on plasma and inductance matrices are
obtained from a plasma current density distribution, which is calculated to satisfy
Grad-Shafranov equation. To design feedback controllers, linear plasma models were obtained
on the Globus-M (Ioffe Inst.) experimental data. Then these controllers were applied on the
developed plasma evolution code. The hierarchical
multi-loop control system includes cascades for
controlling the plasma position and current with
robust SISO PID controllers tuned by QFT [1]. The
outer cascade of plasma shape control incorporates a
plasma reconstruction code, which is created on
moving filaments and has sufficient accuracy and
Fig. 1. Control process of the plasma shape: Br, Bz
speed of response [2]. A plasma shape MIMO in X-point, δΨ1= ΨX‒Ψ1 , δΨ2= ΨX‒Ψ2 , ΨX is the
flux at X-point, Ψ1, Ψ2 are fluxes at the separatrix.
controller was designed by the H∞ robust
loop-shaping approach [3] for magnetic field at X-point Br, Bz and poloidal fluxes on the plasma
separatrix Ψ1, Ψ2. Full thyristor current inverter models operating in self-oscillation mode up to
3 kHz were used as original fast actuators for plasma position control [4]. The plasma shape
controller is turned on at 0.18 s of the discharge and transfers the plasma boundary to the
desired position in less than 5 ms during the divertor phase (Fig. 1). That is critically important
due to comparatively short plasma discharges on the Globus-M tokamak of about 200-250 ms.
[1] Garcia-Sanz M. Robust Contr. Eng.: Practical Quantitative Feedback Theory Solutions, CRC Press, 2017.
[2] Mitrishkin Y.V., Prohorov A.A. Korenev P.S.et al. Proc. IFAC WC, Toulouse, France, pp. 11883-11888, 2017.
[3] McFarlane D. and Glover K. IEEE Trans. Automatic Control, Vol. 37, No. 6, pp. 759-768, June 1992.
th
[4] Kuznetsov E.A., Mitrishkin Y.V., Yagnov V.A., and Shcherbitsky V.N. Proc. 11 IEEE Intern. Conf.
AICT2017, Inst. of Control Sciences, September 20-22, 2017, Moscow, Russia, pp. 485-489, 2017.
