高频空间矢量磁场下超导悬浮系统应用特性研究

The lack of suitable energy storing device for the regenerative braking system is an essential crisis to the subway and light rail system, which is also important for the power saving. The high speed flywheel based on the high temperature superconductive (HTS) maglev bearing has excellent technology advantages compared with the battery and super-capacitor. Furthermore, the flywheel of HTS maglev bearing has superior immunity from interference and self-recovery ability, which is very propitious to the subway system. The alternative fluctuation and inhomogeneous disturb of applied magnetic field will induce fluxes motion and energy loss within the bulk high temperature superconductor (HTSC), which will influence the performance of HTS maglev bearing obviously. The conventional researches based on experiments of time-varying uniform magnetic field and simulation calculation cannot satisfy the requirement of engineering application in the subway system. This project has planned to set up the space vector magnetic field (SVMF) with different frequency by the permanent magnet assembly and driving system. The influence of SVMF on the application performance of bulk HTSC will be researched by the experiment system. Moreover, the particular operation conditions of subway system, such as the relationship among the high frequency SVMF, the self-recovery ability and the performance under frequent acceleration and deceleration, will also be researched by the experiment system. The simulations based on the experimental results will be used to investigate the fluxes motion and loss mechanism within the bulk HTSC deeply, which is help to propose the optimal methods to ensure the safety of subway. The researches of this project are not only the vital engineering basis for the application of HTS maglev bearing in the subway system, but also are the credible references for the high-speed application of HTS maglev system.

地铁及轻轨系统再生制动系统迫切需要合适储能装置进行电能存储，以达到节电目的。以高温磁悬浮轴承为基础的高速飞轮储能器相较于电池、超级电容具有突出技术优势，且抗干扰能力强并具备自恢复特性，非常适合地铁使用。高温超导磁悬浮轴承高速运行时的磁场交变及不均匀性扰动可能引发超导块材内部损耗并影响轴承性能。针对传统均匀时变磁场实验研究及仿真模拟无法满足地铁工程应用的情况，本课题通过特殊设计的永磁阵列组合及驱动系统得到不同波形和交变频率下的空间矢量磁场，研究真实运行条件下高温超导块材悬浮应用特性，并对高频空间矢量磁场下超导块材可恢复特性、频繁加减速特性等地铁特殊需求及关键问题开展实验研究。在实验基础上，结合仿真计算，对超导块材内部磁通运动过程和损耗机制进行深入剖析，提出改进方法，保证地铁应用安全。课题研究内容不仅是高温超导磁浮轴承地铁应用的直接工程依据，亦可为高温超导磁浮技术其它高速应用领域提供科学判据。

本项目针对高温超导磁悬浮高速应用中所面临的问题，开展了高频空间磁场作用下超导块材悬浮系统关键性能研究。采用特殊设计的永磁块阵列构建了半波型、半波-全波复合型、全波型空间矢量磁场，对不同磁场构型下超导磁悬浮系统的力学特性及温升特性进行了实验测试，包含不同交变频率、不同倾角、频繁加减速、外加铁磁性物质扰动、长时间运行等测试内容。建立了超导块材与空间矢量磁场的二维及三维计算模型，对不同磁场构型、频率、强度以及空间位置等参数影响下的块材内部损耗特征及温升机理进行了研究。研究结果表明，空间矢量磁场作用下的超导块材内部损耗及温升特征与均匀磁场作用下存在较大差异。具有磁力线闭合特征的空间磁场，在相同强度及频率下，所造成的超导块材内部损耗要高于具有磁力线发散特征的空间磁场。全波型空间矢量磁场在低频下所造成的超导块材内部损耗要远高于半波型及半波-全波复合型磁场。超导块材内部损耗会随倾角增大而降低。铁磁性扰动的引入，在不同磁场结构及测试状态下会造成不同的影响结果。相较于半波型磁场，在全波型及半波-全波复合型磁场下，需要经历更多次数的加减速过程，超导块材内部的悬浮力及温升特性才能趋于稳定。在项目使用期间，超导块材的弛豫特性，即磁通钉扎性能未发生明显改变。项目的主要科学意义在于，通过高频空间磁场的引入与研究，可以理解超导块材在高速应用状态下，磁场不均匀性对其悬浮性能的影响，相关研究具有较强普适性，可以用于直线型及旋转型应用系统。相关结果表明，磁场构型是决定空间磁场对超导块材内部损耗影响的关键因素。在低频下，全波型磁场会带来较大的损耗，造成悬浮力的大幅下降，并且需要更长的加减速过程才能使块材悬浮性能趋于稳定，因此在实际工程应用中，应当注意避免引入类似结构磁场不均匀性的引入。此外，仿真及测试结果均表明，高频空间磁场作用下的起始50 s时间内是损耗及温升增长最快的时段，在实际应用中应当予以重点关注。