Research On Key Technologies Of Large-scale Double-Stator Superconducting Field Modulation Wind Generator

With the gradual maturity of the onshore wind power industry,the development focus of wind power is gradually shifting to the development of offshore wind energy.In order to improve the reliability and economy of offshore wind power,large-capacity direct drive has become the main development trend of offshore wind turbines.However,due to the low rated speed of the high-power direct-drive wind turbine,its volume and weight are much higher than that of the traditional non-direct-drive unit,and it faces huge challenges in machine design,manufacturing,transportation and installation.Superconducting machines are a potential solution for the industrialization of large-capacity direct-drive offshore wind turbines due to their advantages of high torque density,light weight,small size and high efficiency.However,due to the existence of rotating excitation or rotating armature windings in traditional electrically-excited superconducting synchronous machines,devices such as rotating power supply,rotating cooling or brush slip rings are inevitably introduced,which greatly increases the complexity of the machine system structure and reduces the reliability of the system.The double-stator magnetic field modulation machine has a structure without rotating windings,and the system is simple and reliable.Under this backgrounds,this paper conducts in-depth research on the key design technology of large-scale double-stator superconducting magnetic field modulation wind turbines.The main research contents and contributions are as follows:1.Aiming at the problem of rotating windings in superconducting synchronous machines,a double stator superconducting magnetic field modulation machine topology with an integer slot distributed winding structure is proposed.On this basis,the feasibility of the large-scale double-stator superconducting magnetic field modulation generator was verified,and the electromagnetic performance analysis and electromagnetic scheme design of the dual-stator superconducting magnetic field modulation generator were completed.This article firstly reviews and summarizes the structure and working principle of existing superconducting machines at home and abroad,and selects the double-stator superconducting magnetic field modulation machine as the research topology based on the comparison of the basic performance of various topologies.Secondly,based on the classical magnetic field modulation theory,an in-depth study of the working characteristics of the dual-stator magnetic field modulation machine is carried out,explaining the reason why the machine can still complete the torque output when the excitation and armature windings are stationary.In addition,the different derived topologies and armature winding structures of large-scale double-stator magnetic field modulation machines are compared in detail,and a doublestator superconducting magnetic field modulation machine topology with an integer slot distributed winding structure is proposed.At the same time,the electromagnetic design process of the topology is explained in detail,and the optimization design of the large-scale double stator magnetic field modulation machine is completed.2.Aiming at the problem of large AC loss of the double-stator superconducting magnetic field modulation machine,a combination of copper shielding layer and magnetic flux diverter was proposed to suppress the AC loss of the superconducting coil,and a good suppression effect was achieved.Firstly,through the analysis of the alternating magnetic field around the superconducting coil,the reason for the large AC loss in the superconducting coil of the machine is explained.Secondly,the anisotropy of the AC loss of the high-temperature superconducting strip is analyzed,and the main parameters that affect the AC loss are obtained.At the same time,in order to accurately and quickly calculate the AC loss of the superconducting coil in the machine,a fully coupled finite element simulation model is established.On this basis,two methods to suppress the AC loss of superconducting coils are proposed,and the suppression effect of each method is studied in detail.Finally,by adopting a combination scheme of copper shielding layer and magnetic flux diverter,the suppression of AC loss is completed.3.In response to the compact structure of the machine modular cryostat,a simple,reliable and easy-to-install cryostat structure is proposed.Based on the analysis of the AC loss of the superconducting coil and the working characteristics of the machine,the components of the cryostat are designed and analyzed.In order to facilitate the installation,an extruded support structure is proposed.Through the segmented assembly of the outer wall of the thermostat,the problem of difficult installation of the support structure of the thermostat is solved.Based on the completion of the structural design,a distributed cooling scheme was proposed,and the calculation of the cooling power of the cryostat and the evaluation of the thermal stability of the superconducting coil were completed.4.Completed the overall design plan of the 10 MW double-stator superconducting magnetic field modulation generator,including the detailed size of the machine and the weight and cost of each component.Secondly,by comparing the performance parameters of the dualstator superconducting magnetic field modulation machine with the existing 10 MW superconducting synchronous machine scheme,it proves the feasibility and application potential of large-scale double-stator superconducting magnetic field modulation wind turbines.In addition,the operating characteristics of the fan under different wind conditions and rotor speeds are studied.In summary,this article has conducted an in-depth study on the large-scale double-stator superconducting magnetic field modulation machine from theoretical analysis,electromagnetic design,AC loss suppression and cryostat design,and completed the design scheme of a 10 MW double-stator superconducting magnetic field modulation generator.Provides theoretical support and technical guidance for the development of large-scale offshore superconducting wind turbines.