Novel DC/DC Chopper Used In Superconducting Magnetic Energy Storage System

During the dynamic operation of HTS magnetic energy storage,the HTS magnet is subject to high frequency pulse voltage.Because of the existence of stray capacitance and ground capacitance in the magnet,the high frequency pulse voltage will not be uniformly distributed in the magnet,and the transient overvoltage will be withstood inside the magnets.Excessive transient voltage will accelerate insulation aging and even lead to insulation breakdown,threatening the safety of the device.Therefore,the accurate evaluation of the characteristics of voltage distribution in superconducting magnets is helpful to improve the insulation design of magnets,and it is of great significance to study methods to suppress or even eliminate overvoltages,which is of great significance to improve the safety and stability of superconducting magnetic energy storage devices.On the basis of modeling and experimental analysis of transient voltage distribution characteristics of superconducting magnets,a novel DC/DC chopper topology for superconducting magnetic energy storage devices is studied and analyzed in this paper.In this new topology,superconducting magnets will no longer withstand high frequency pulse voltage,thus eliminating the problem of overvoltage.Specifically,the work carried out in this paper is as follows:(1)The lumped parameter model of superconducting magnets is established.The calculation method of circuit parameters in the model and the method of calculating the voltage distribution characteristic of superconducting magnet based on this model are analyzed.An experimental platform was set up to measure the voltage distribution characteristics of a superconducting magnet subjected to steeply rising step voltage.The characteristics of overvoltage distribution inside the magnet were demonstrated intuitively by experiments,and the validity of the established simulation model was verified.(2)The circuit topology and working principle of traditional DC/DC chopper and new DC/DC chopper used in superconducting magnetic energy storage device are analyzed,the mathematical model and small signal model are established,the control strategies of these two choppers are analyzed,and the simulation analysis is completed.The correctness of the control design is verified.(3)The hardware design,software design and prototype development of 60V/30 A DC/DC chopper are completed.The prototype can simulate the working process of the traditional DC/DC chopper and the new DC/DC chopper respectively.In both modes,the speed of charging or discharging the load magnet can be effectively controlled,and the power command can be quickly responded to.Based on the prototype,the magnets charging experiment and power exchange experiment are completed.According to the experimental results,the advantages and disadvantages of the two choppers are compared and analyzed,and the feasibility of the new DC/DC chopper topology is verified.