Study On AC Losses Of High Temperature Superconducting Coated Conductor

Superconducting power technology is a cutting-edge technology that plays a very important role in power industry.High temperature superconductor has characteristics of small volume and high carrying capacity.As the current carrying conductors used in large capacity or low loss transmission has a broad prospect.However,at present,the superconductor must be used in the low temperature environment.And the existence of the loss of superconductors not only will increase the cooling costs,but also reduce the stability of superconducting power equipment.So,it is very important to study the AC loss of HTS coated conductors.In this thesis,the research background and the current research status of the AC loss of HTS coated conductors are described in detail.From the theoretical aspect,the loss of the high temperature superconductor in the field of self field,DC background field and AC background is analyzed in detail.The causes and types of the losses are described and the method of reducing the AC loss of HTS coated conductors is described.On the basis of theoretical analysis,the theoretical calculation model of AC loss is listed,such as Norris model.The theoretical model is calculated,and the frequency characteristic curve of AC loss is drawn.The finite element simulation software COMSOL was used to simulate the self field loss of HTS coated conductor.The current density distribution in the strip is obtained when the AC current is transferred.The simulation value of the AC loss is obtained.The reliability and validity of the simulation is verified by comparing the theoretical value with the data of the Norris equation.The measurement method of AC loss of HTS coated conductors is described systematically.The principle of the three measurement methods is analyzed in detail,and the advantages and disadvantages of various measurement methods are compared.Based on the existing experimental conditions,the AC loss measurement platform of self field,DC background field and AC background field is built.The advantages and disadvantages of the platform are analyzed,and the error of the platform is analyzed.And an improved scheme for the existing experimental platform is proposed.In the liquid nitrogen environment(77K),the loss of Bi high Tc superconducting coated conductors and YBCO superconducting coated conductors were measured.By drawing and analyzing the experimental data,it is found that the experimental data isin good agreement with the theoretical model.The reasons of the deviation between the experimental data and the theoretical data are analyzed.The similarities and differences of the AC losses of the two kinds of superconductors are compared and analyzed,and the specific reasons are explained.The characteristics of the AC loss of HTS coated conductors and the influence of the DC background field and the AC background field are obtained.