Design And Analysis Of Power Supply And Magnet Protection System Of CFETR CS Model Coil

Nuclear fusion energy is the ideal new energy in the future.At present,research on the development of fusion energy has made breakthroughs in tokamak type magnetic confinement experimental devices.China Fusion Engineering Experimental Reactor(CFETR),which has a fully superconducting tokamak type,is a new fusion engineering experimental reactor independently designed by China.It will lay the foundation for the construction of a prototype fusion power station in China.The central solenoid(CS)coil is the key component of the CFETR magnet system.Its maximum magnetic field during operation is 12T,and its maximum variation rate of the magnetic field reaches to 1.5T/s.In order to develop the key engineering technologies for large-scale superconducting magnets,we developed the CS model coil and established a large-scale low-temperature test platform.When the CS model coil is manufactured,a series of experiments will be conducted to study and evaluate the performance of the coil.As an important part of the test platform,the power supply system will provide the required test current for the coil and provide conditions for the performance test of the coil.At the same time,the energy stored in the CS model coil is about 407MJ.If the energy in the coil was not released quickly when a quench occurred,it would damage the superconducting coil and the experimental device,which would be incalculable loss.Therefore,the quench protection system is an important part of the power supply system.The design and development of the quench protection system is of great significance for the safe and reliable operation of the CS model coils.Firstly,this paper analyzes the characteristics of the test current waveform.The ITER DC test platform rectifier and PF converter are used as the experimental power supply,and the topology of the main circuit of the power supply system is designed to meet the test requirements,high current(47.65kA)and rapid change of current(5.96kA/s),of the CS model coil.For the different operating modes of the power supply,corresponding control strategies are proposed,and a MATLAB/Simulink simulation model is built to simulate the main circuit to verify the feasibility of the main circuit design.The main components such as the commutation resistor of the switching network unit in the main circuit are calculated.Through analysis and comparison,the two-stage commutating current technology is used to solve the technical difficulties that the circuit breaker cannot directly break the high DC current.The commutating process of the breaker to the fuse is analyzed in theory.And the factors that affect the commutation are analyzed.Secondly,according to the parameters of the quench protection system of the CS model coil,the system design is carried out,and the key components in the quenchprotection system are analyzed,designed and implemented.A 50kA DC rapid circuit breaker is developed as the quench protection breaker,and its basic structure,working principle and performance test are introduced.Through theoretical analysis and calculation,the size of the high-powered resistor is calculated,the material of it is selected,and the structural design and implementation of the resistor is completed.As for the fuse,the parameter calculation,structure design and manufacture of it are completed,and at the same time the diode's parameter calculation,selection and procurement are also completed.Then,a safe and reliable quench protection control system is designed.The reliability of the electronic circuit of the hardware protection system is qualitatively and quantitatively analyzed by fault tree and reliability block diagram.The design provides theoretical guidance and basis for the reliability design and implementation of the hardware protection system.Finally,the experimental study of the quench protection breaker is conducted.The thermal stability and breaking performance test schemes were designed,and the overheating phenomenon during the thermal stability experiment of the quench protection breaker under the current of 30 kA is analyzed.The improvement measures were proposed.These measures can effectively improve the thermal stability of the quench protection switch,which will be verified through follow-up experiments.