A long-standing mystery in the study of Field-Aligned Currents(FACs) has been that: how the currents are generated and why they appear to be much stronger at high altitudes than in the ionosphere. Here we present two ...A long-standing mystery in the study of Field-Aligned Currents(FACs) has been that: how the currents are generated and why they appear to be much stronger at high altitudes than in the ionosphere. Here we present two events of magnetotail FACs observed by the Magnetospheric Multiscale Spacecraft(MMS) on 1 st July and 14 th July 2016, to show how the Substorm Current Wedges(SCW) were formed. The results show that particles were transferred heading towards the Earth during the expansion phase of substorms.The azimuthal flow formed clockwise(counter-clockwise) vortex-like motion, and then generated downward(upward) FACs on the tailward/poleward side of the distorted field with opposite vorticity on their Earthward/equatorward side. We also analyzed the Region 1 FACs observed by the Earth Explorer Swarm spacecraft on 1 st July 2016 and found that they were associated with FACs observed by MMS, although differing by a factor of 10. This difference suggests that either there was the closure of the currents at altitudes above 500 km or the currents were not strictly parallel to B and closed at longitudes away from where they were generated.展开更多
交替极永磁(consequent pole permanent magnet,CPPM)电机每对极下的气隙磁密不对称,在特定极槽配合下其反电动势(electromotive force,EMF)中存在2、4次等偶次谐波分量,引起额外的转矩脉动,降低转矩输出品质。为解决上述问题,提出一种...交替极永磁(consequent pole permanent magnet,CPPM)电机每对极下的气隙磁密不对称,在特定极槽配合下其反电动势(electromotive force,EMF)中存在2、4次等偶次谐波分量,引起额外的转矩脉动,降低转矩输出品质。为解决上述问题,提出一种注入多谐波电流产生的转矩补偿原有转矩脉动的控制策略。推导适用于任意次谐波磁链产生的转矩脉动通用解析模型;并基于此模型,给出利用谐波电流抑制转矩脉动的理论依据;提出在同步旋转坐标系下注入多次谐波电流的方法,抑制由2、4、5、7、11、13次谐波反电势引起的3、6、12次转矩脉动;并利用准-比例谐振控制器实现谐波电流的精确跟踪。最后,以一台三相9槽10极交替极永磁电机为例,通过不同工况下的转矩脉动抑制实验,验证所提控制策略的有效性。展开更多
基金Supported by National Natural Science Foundation of China(41874190,41231066)
文摘A long-standing mystery in the study of Field-Aligned Currents(FACs) has been that: how the currents are generated and why they appear to be much stronger at high altitudes than in the ionosphere. Here we present two events of magnetotail FACs observed by the Magnetospheric Multiscale Spacecraft(MMS) on 1 st July and 14 th July 2016, to show how the Substorm Current Wedges(SCW) were formed. The results show that particles were transferred heading towards the Earth during the expansion phase of substorms.The azimuthal flow formed clockwise(counter-clockwise) vortex-like motion, and then generated downward(upward) FACs on the tailward/poleward side of the distorted field with opposite vorticity on their Earthward/equatorward side. We also analyzed the Region 1 FACs observed by the Earth Explorer Swarm spacecraft on 1 st July 2016 and found that they were associated with FACs observed by MMS, although differing by a factor of 10. This difference suggests that either there was the closure of the currents at altitudes above 500 km or the currents were not strictly parallel to B and closed at longitudes away from where they were generated.
文摘交替极永磁(consequent pole permanent magnet,CPPM)电机每对极下的气隙磁密不对称,在特定极槽配合下其反电动势(electromotive force,EMF)中存在2、4次等偶次谐波分量,引起额外的转矩脉动,降低转矩输出品质。为解决上述问题,提出一种注入多谐波电流产生的转矩补偿原有转矩脉动的控制策略。推导适用于任意次谐波磁链产生的转矩脉动通用解析模型;并基于此模型,给出利用谐波电流抑制转矩脉动的理论依据;提出在同步旋转坐标系下注入多次谐波电流的方法,抑制由2、4、5、7、11、13次谐波反电势引起的3、6、12次转矩脉动;并利用准-比例谐振控制器实现谐波电流的精确跟踪。最后,以一台三相9槽10极交替极永磁电机为例,通过不同工况下的转矩脉动抑制实验,验证所提控制策略的有效性。
