Research On The Generation And Regulation Method Of Flat-top High Magnetic Field

As an extreme physical enviornment,the strong magnetic field has a wide range of applications in scientific research,medical and military industries.The flat-top pulsed high magnetic field(FPHMF)has the advantages of small field ripple and long duration of steadystate high magnetic field,and the andvantages of high strength and low operating cost of pulsed high magnetic field.Therefore,the study of the FPHMF is of great significance.In this paper,based on extensive reading of relevant literature,with the goal of improving the performance of the FPHMF,the generation and control of the FPHMF system are studied in depth.The capacitor power supply(CPS)has the advantages of high energy storage efficiency,low loss,and simple control.There fore,this paper proposes a new topology circuit that generates a FPHMF based on the CPS’s sequential discharge.This topology circuit can adjust the pulse width of the FPHMF according to how many the CPS bank are put in.Based on the established mathematical model of the power supply and magnet system,the parameter scanning method is used to optimize the FPHMF with the longest pulse width as the singletarget,and the genetic algorithm(GA)is used to optimize the FPHMF with the longest pulse width as the single-target to verify the feasibility of the algorithm.The GA is used to optimize the FPHMF with single-objective optimization with the highest accuracy as the goal,and the change of parameters to further improve the stability.In order to further increase the field strength and the pulsed width of the FPHMF,a hybrid power supply consisting of generator-retifier power supply(GRPS)and CPS was designed.Aiming at the single-coil magnet,the CPS and the GRPS are connected in parallel in a timeseries power supply mode,and the design process of the FPHMF system is elaborated in detail.The visual optimization design method of the quasi-circle mapping is introduced to carry out the many-objective optimization design of the FPHMF system.For the dual-coil magnet,a hybrid power supply method is designed.The working process is analyzed and the control strategy is optimized considering the influence of mutual inductance voltage.A FPHMF with a longer pulse width can be relized.In the research of active regulation systems,an active regulation system based on the principle of magnetic field compensation is designed to track the magnetic field ripple at the flat-top stage online and compensate for its fluctuation.The control system uses a full-bridge inverter circuit based on supercapacitors,which can achieve two-way compensation for the magnetic of the system.In order to avoid the overcompensation caused by the excessive multual inductance voltage of the control system,a smoothing inductor can be connected in series in the discharge circuit.And the experimental platform of the control system is completed.Hysteresis control and triangular carrier control are used to control the FPHMF of the capacitor power supply,which can improve the accuracy to below 100 ppm.The hybrid power single coil magnet system and the combined power double coil magney system can improve the accuracy to below in 100 ppm in single-coil magnet FPHMF system and 150 ppm in dual-coil magnet FPHMF system.