| In controlled nuclear fusion research based on tokamak,because the tearing mode(TM)can lead to mode locking and major disruption,which will affect the device’s stable operation,the control of the TM is one of popular studies in today’s fusion field.It has been found that real-time feedback controlling the TM via magnetic perturbation can accelerate and stabilize the TM.This method requires that the magnetic perturbation should be applied in the fixed phase interval of the TM in real time.It also requires the power supply to generate required magnetic perturbation should have rapid rising and falling edges,and the frequency and duty cycle can be variable at any time to achieve real-time tracking of the TM’s phase.In order to verify the new method of controlling the TM on the J-TEXT device,a current-pulsed power supply(CPPS)for the magnetic perturbation coils is developed to generate the magnetic perturbation which satisfies the physical experiment requirements.Based on the demand of TM real-time feedback control experiment on the J-TEXT tokamak,and combined with the working principle of stochastic field experiment power supply and classical buck chopper circuit,the main circuit topology of CPPS with rapid rising and falling edges is raised.The topology makes use of the charged large inductance and its freewheeling circuit to form a current source,and the rapid rising edge of current can be realized by the fast switching of the IGBT.It builds the discharge branch with very small discharge time constant to realize the rapid falling edge of the current.The working principle of the power supply is analyzed in four stages.For the development of the high power resistance with small parasitic inductance,the optimization from the nichrome resistance to the graphite resistance is successfully realized.To absorb the IGBT’s turn-off spike voltage caused by parasitic inductance in the actual circuit,thick-film resistors,thin-film capacitors and schottky diode with ultrafast recovery time are applied in the RCD snubber circuit whose structure and parameter are also designed.In order to provide a stable DC voltage,a scheme of DC power supply based on the capacitor energy storage is chosen.The realization of the power supply is divided into two stages,in the early attempt stage of power supply,the consistency of the MATLAB/Simulink simulation results and power supply test results has verified the validity and feasibility of the design of CPPS;during the upgrade stage of the power supply,IGBT’s turn-off peak voltage is declined from 2500 V before upgrading to 1600 V,and the power supply’s frequency is increased from3 kHz before upgrading to 6kHz.Eventually,the power supply has been put into the formal physical experiment of feedback control TM on the J-TEXT tokamak,the power supply can run safely and stably.And it has successfully output current pulses with the frequency that range from 1kHzto 6kHz,amplitude that reaches 1kA,duty cycle that range from20% to 50%,the rising time of 60μs and the falling time of 50μs.It is proved by several physical experiments that the power supply can respond to the rotation of the magnetic island quickly,and the synchronous cooperation between the power supply and the magnetic island can be realized.As expected,the design goals have been reached,and the typical experimental phenomena,such as accelerating and decelerating the magnetic island when the magnetic perturbation is applied in the different phase interval,have also been obtained. |
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