島田 勝弘; 寺門 恒久; 山内 邦仁; 松川 誠; Baulaigue, O.*; Coletti, R.*; Coletti, A.*; Novello, L.*
Plasma Science and Technology, 15(2), p.184 - 187, 2013/02
In JT-60SA, the four thyristor converters in poloidal field coil (PFC) power supplies are used for plasma initiation. In this case, the large reactive power fluctuation induced by the "Booster PS" is the cause of large voltage fluctuation across the terminals of the motor-generator. To minimize the reactive power fluctuation during plasma initiation, an asymmetric control method and a sequential timing control to start/stop each "Booster PS" are foreseen. To evaluate the effectiveness of above control methods for the "Booster PS", the reactive power has been simulated by using "PSCAD/EMTDC" code. From the simulation it results that the reactive power induced by the four units of the "Booster PS" can be dramatically reduced. In addition, the voltage fluctuation of the motor-generator connected to the "Booster PS" is expected to be suppressed to less than 10%, which ensures the stable control of JT-60SA magnet power supplies.
山内 邦仁; 島田 勝弘; 寺門 恒久; 松川 誠; Coletti, R.*; Lampasi, A.*; Gaio, E.*; Coletti, A.*; Novello, L.*
Plasma Science and Technology, 15(2), p.148 - 151, 2013/02
One of the most essential issues for designing a power supply system of superconducting coil is to avoid any overvoltage. Here, the most concerned overvoltage can appear between turns due to the transiently concentrated voltage distribution inside the coil, which is mainly caused by parasitic capacitances and high dv/dt. For this reason, the coil power supply, especially fast high voltage generation circuit, should equip proper snubber(s) in order to suppress the dv/dt. However, it is too complicated to accurately evaluate the transient voltage in the coil because of the distributed parameters of the mutual inductance between turns and the capacitance between adjacent conductors. In this study, such a complicated system is modeled with reasonably detailed circuit network with lumped ones, and is integrated into the overall simulation model of JT-60SA PF coil circuit. Then a detailed circuit analysis is conducted in order to evaluate the possible voltage transient in the coil circuit. As a result, appropriate circuit parameters in the coil power supply including the snubbers are obtained.
島田 勝弘; Baulaigue, O.*; Cara, P.*; Coletti, A.*; Coletti, R.*; 松川 誠; 寺門 恒久; 山内 邦仁
Fusion Engineering and Design, 86(6-8), p.1427 - 1431, 2011/10
In the initial research phase of JT-60SA, the plasma heating operation of 30MW-60s or 20MW-100s is planned for 5.5 MA single null divertor plasmas. To achieve this operation, AC power source of the medium voltage of 18 kV and 7 GJ has to be provided in total to the poloidal field coil power supplies and additional heating devices such as Neutral Beam Injection (NBI) and Electron Cyclotron Radio Frequency (ECRF). In this paper, the proposed AC power supply system in JT-60SA was estimated from the view point of available power, and harmonic currents based on the standard plasma operation scenario during the initial research phase. This AC power supply system consists of the reused JT-60 power supply facilities including motor generators with flywheel, AC breakers, and harmonic filters, etc. to make it cost effective. In addition, the conceptual design of the upgraded AC power supply system for the ultimate heating power of 41MW-100s in the extended research phase is also described.
Coletti, A.*; Baulaigue, O.*; Cara, P.*; Coletti, R.*; Ferro, A.*; Gaio, E.*; 松川 誠; Novello, L.*; Santinelli, M.*; 島田 勝弘; et al.
Fusion Engineering and Design, 86(6-8), p.1373 - 1376, 2011/10
JT-60SA is a joint international research and development project involving Japan and Europe, in the frame of the "Broader Approach Agreement", for the construction and operation of a new tokamak intended to prepare and support ITER operation. JT-60SA is to be built in Naka, Japan, using existing infrastructures and subsystems of the former JT-60U experiment, as much as possible. SA, as "super advanced", refers to the use of Superconducting Coils Magnets (SCM) and to the study of advanced modes in plasma operation. The SCM system includes Toroidal and Poloidal Field Coils (TFC and PFC respectively). In addition the machine features a number of normal conducting coils: Fast Plasma Control Coils (FPCC), a Resistive Wall Mode Control Coils and the Error Field Correction Coils. The paper describes the main features of the JT-60SA SCM Power Supply System (SCMPS) with special regard to coil current regulation mode and SCM protection.
島田 勝弘; 寺門 恒久; 松川 誠; Cara, P.*; Baulaigue, O.*; Gaio, E.*; Coletti, R.*; Candela, G.*; Coletti, A.*
Journal of Plasma and Fusion Research SERIES, Vol.9, p.163 - 168, 2010/08
This paper describes the stable coil current control method of back-to-back thyristor converters as a design study. The back-to-back thyristor converter is applied to "Base PS" which is low-voltage power supply for PF coil in JT-60SA. This converter has six arms of anti-parallel connected thyristor devices to enable to operate with 4 quadrant operation. The dead beat control method is applied on the current feedback control algorithm. In addition, the non-interacting control method is adopted between coil current and circulating current among converters, which is necessary for smooth reversing of the coil current polarity. The rate limiter for control angles of thyristor converter is introduced to suppress the excessive current unbalance between converters. To estimate the proposed coil current control method, the real "Base PS" models are simulated by "PSCAD/EMTDC" code. From the simulation results, the stable control capability was obtained.
山内 邦仁; 島田 勝弘; 寺門 恒久; 松川 誠; Cara, P.*; Gaio, E.*; Santinelli, M.*; Coletti, R.*; Coletti, A.*
Journal of Plasma and Fusion Research SERIES, Vol.9, p.220 - 225, 2010/08
High current of about 500 kA will be induced in the passive structures such as vacuum vessel and stabilizing plate at plasma initiation in JT-60SA, because the total resistance of the passive structure is approximately 16 and the breakdown electric field of 0.5 V/m is expected for stable plasma initiation from the experiments of JT-60U. Therefore, a precise evaluation of the magnetic field performance using the accurate circuit analysis model has to be conducted to obtain stable plasma breakdown and for designing the detail of power supply system. In this paper, the preparation procedure of the analysis model will be presented. Then, some circuit analysis results of plasma breakdown will be given using ideal power supply and actual thyristor converter model for comparison. The delay effect of converter voltage control and the discrepancy of current control would be summarized as the first achievement. The voltage fluctuation of generator (H-MG, 400 MVA) at plasma initiation will be also described, because large reactive power fluctuation may cause large voltage fluctuation and sudden phase shift of the AC source voltage of thyristor converter.
松川 誠; 寺門 恒久; 山内 邦仁; 島田 勝弘; Cara, P.*; Gaio, E.*; Novello, L.*; Ferro, A.*; Coletti, R.*; Santinelli, M.*; et al.
Journal of Plasma and Fusion Research SERIES, Vol.9, p.264 - 269, 2010/08
Reliable plasma initiation is very important in the nuclear fusion devices especially in superconducting tokamaks. Applicable breakdown electric field would be limited up to level of 0.5 V/m to suppress large AC losses in the superconducting magnet. Furthermore, induced current in the passive structure such as vacuum vessel and stabilizing plate would increased easily to the comparable level of plasma current with several hundred kA even in the case of ECH assist breakdown. Therefore, optimization of the applied voltage to the poloidal field coil is necessary for stable plasma initiation. In this paper, the rationalized plasma initiation scenario using cost effectively designed power supply system will be provided.
松川 誠; 菊池 満; 藤井 常幸; 藤田 隆明; 林 孝夫; 東島 智; 細金 延幸; 池田 佳隆; 井手 俊介; 石田 真一; et al.
Fusion Engineering and Design, 83(7-9), p.795 - 803, 2008/12
山内 邦仁; Baulaigue, O.*; Coletti, A.*; Coletti, R.*; Ferro, A.*; Gaio, E.*; Lampasi, A.*; 松川 誠; Novello, L.*; 島田 勝弘; et al.
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The JT-60SA tokamak device consists of superconducting toroidal field (TF) and poloidal field (PF) coils, and some in-vessel coils. All of 18 TF coils are connected in series and powered by a low-voltage unidirectional DC power supply (PS), while three Quench Protection Circuits (QPCs) are inserted for every six TF coils. Meanwhile, each PF coil circuit is independent from the others, and a bidirectional DC current is driven for plasma current ramp-up and sustainment by series-connected Base PS, and Switching Network Unit or Booster PS. TF coils are energized by commercial electric power grid directly, but the rest of the coils are planned to be powered by the existing motor-generator of JT-60. This paper describes the key features and the expected performances of the main PS system for the superconducting magnets in JT-60SA.