The Study Of Design And Operation Characteristics For Pulsed Magnetic Power Supplies In Tokamaks

The magnetic power supply system is an important component for a tokamak device. It is mainly used to energize magnetic coils in the tokamak device to maintain required magnetic field for plasma confinement. Hence the technologies of designing, controlling and operating the power supply system are greatly responsible for the safety, stability and efficiency of the tokamak device and future fusion reactors. J-TEXT (Joint Texas Experimental Tokamak, formerly known as TEXT-U in Texas University) is a regular medium sized tokamak device. It can provide a350kA plasma discharge within500ms. The typical operation of J-TEXT is a pulsed style, which requires all its magnetic power supplies designed and operated with the pulsed operation pattern.The manuscript presents the design and realization of a pulsed magnetic power supply system for the divertor system of J-TEXT. This power supply system also works as a fundamental to study real-time control technologies, as well as operation characteristics of power supplies of this kind. The detailed works are discussed in following contents:The design and realization of the pulsed magnetic power supply system put the emphasis on exploring guidelines in optimizing parameters of components under pulsed power conditions. The thermal circuit method and the instantaneous thermal resistance parameter are used for designing thyristor parameters, which is a main advantage of the work.A controller prototype is designed and realized according to the requirements of J-TEXT COD AC system. This prototype is based on the industrial PC hardware platform and the QNX operating system. It works with PSH in J-TEXT CODAC system, and provides successful control performance for the divertor power supply system. This prototype design has been applied to existing J-TEXT power supply controllers successfully.The state space control model for the power supply is firstly obtained, and then a simplified current feedback control strategy is proposed. This strategy introduced a linear restriction to the input parameters to simplify the state space model to a SISO model. The coupling in the model is eliminated, meanwhile the loads in different rectifiers are balanced. This control strategy is validated in experiments.The current commutation in pulsed magnetic rectifier is well studied. The complete operation characteristics are obtained with the detailed study to the commutation with the overlap angle greater than60°. The commutation concerning the ac line resistance is also discussed, and the formulas of output parameters are presented. The theories match the experiment results well.The effects of harmonics in synchronization signals of the rectifier is also studied. The harmonic analysis is performed to obtain the spectrum of arbitrarily picked synchronization signal. The distortion factor is introduced to distinguish different harmonic effects. Analysis show that the fundamental harmonic is responsible for synchronization delay, meanwhile higher harmonics may cause unpredictable synchronization shifts.This manuscript has studied the technologies for designing and operating a pulse magnetic power supply system. Then the divertor power supply system and its control system are realized. They perform well in experiments. The proposed real-time controller inherits and improves existing ITER I&C designs, and may provide a good reference for similar controller design in ITER and future fusion reactors. The study on pulsed rectifier characteristics is widely applicable in fields like parameter design, synchronization design, controller design, and operation analysis in high power rectifier applications.