Optimal Design Of High Temperature Superconducting Magnetic Energy Storage Magnet

High-temperature superconducting magnetic energy storage(HTS-SMES)system has unique advantage in improving power supply quality and power system stability due to its high energy storage density,high power density,strong power compensation capability and low refrigeration cost.The hightemperature superconducting energy storage magnet is the core component of HTS-SMES.Its electromagnetic optimization design is beneficial to increase the total energy storage and energy storage density of the magnet,and increase the economic and rationality of the design.Therefore,electromagnetic optimization of the SMES magnet is particularly important.Bi-based superconducting materials have more mature applications in HTS-SMES,but their obvious electromagnetic anisotropy makes their irreversible field low,and the critical current is susceptible to magnetic fields.Compared with Bi-based superconducting materials,YBCO has good high-temperature magnetic field characteristics,high critical current density characteristics and weak electromagnetic anisotropy,so it is the better choice for designing high-temperature superconducting energy storage magnets.Single solenoid magnets,parallel multisolenoid magnets and ring magnets are three basic structures for SMES magnet design.Single solenoid magnets are chosen as the structure for SMES magnets due to the advantages of high material utilization and high energy storage density.In this paper,the structural parameters of a single solenoid SMES magnet,the volume energy density,and the simulated annealing genetic algorithm are used as the design variables,the optimization target and the optimization algorithm,respectively.The LiveLink for MATLAB data interface of COMSOL software is used to establish the joint optimization based on MATLAB and COMSOL.The algorithm is used to calculate the optimal geometric parameters of a single solenoid superconducting magnet under a given 500 m superconducting tapes at 77 K operating temperature.According to the magnetic field distribution of the single solenoid SMES magnet,the stepped-section magnet structure is adopted to change the flux line path of the magnet,thereby the maximum radial magnetic field is reduced and the critical current and volume energy density of the magnet is increased.Compared with the single solenoid superconducting magnet,the volume energy density of the magnet with the outer step-shaped cross section,the inner-shaped cross section and the inner and outer step-shaped cross section increased by 4.623%,6.868% and 9.713%,respectively.Therefore,the magnet with inner and outer step-shaped cross section has a better effect in increasing volumetric energy density.According to the radial magnetic field distribution of the magnet with inner and outer step-shaped cross section,the maximum current allowed to enter at different step heights is calculated and a step current is applied.The volume energy density of the magnet with inner and outer step-shaped cross section with different step currents increased by 8.459% with the same magnet structure.