The free Fisher information of an operator random matrix is studied. When the covariance of a random matrix is a conditional expectation, the free Fisher information of such a matrix is the double of this conditional ...The free Fisher information of an operator random matrix is studied. When the covariance of a random matrix is a conditional expectation, the free Fisher information of such a matrix is the double of this conditional expectation’s Watatani index.展开更多
This paper studies the behavior of a reinforced concrete(RC)structural frame employing a tessellated structuralarchitectural(TeSA)shear wall as the lateral-load resisting element.TeSA walls are made of interlocking mo...This paper studies the behavior of a reinforced concrete(RC)structural frame employing a tessellated structuralarchitectural(TeSA)shear wall as the lateral-load resisting element.TeSA walls are made of interlocking modules(tiles)that provide easier repairability and replaceability.A nonlinearfinite element model of a TeSA wall with tiles interlocking in one direction(1-D interlocking)is validated using test data.An RC frame from a building is modeled with a 1-D interlocking TeSA shear wall.The effects of varying rigidity of the wall-frame connections(rigid,hinged,slotted)on the lateral strength of the system and the axial load demands of the gravity-load resisting systems are evaluated.Finally,the effect of connection details on the damage of the TeSA wall is also studied.The study shows that the lateral strength of the system is the highest with a rigid connection between the wall and the system,followed by the system with hinged connections.Slotted connections,which provided no vertical coupling between the wall and the frame result in the lowest lateral strength.TeSA wall experienced“slight damage”up to a drift ratio of 2%.The system with rigid connections between the wall and the frame experienced the most damage,followed by system with hinged and slotted connections.展开更多
为抑制模块化多电平换流器(modular multilevel converter,MMC)内部的三相环流,在MMC内部数学模型的基础上,采用二倍频负序旋转坐标变换将换流器内部的三相环流分解为2个直流分量,并设计了相应的环流抑制控制器(circulating current sup...为抑制模块化多电平换流器(modular multilevel converter,MMC)内部的三相环流,在MMC内部数学模型的基础上,采用二倍频负序旋转坐标变换将换流器内部的三相环流分解为2个直流分量,并设计了相应的环流抑制控制器(circulating current suppressing controller,CCSC),从而消除了桥臂电流中的环流分量,大大减小了桥臂电流的畸变程度,使其更逼近正弦波。最后通过PSCAD/EMTDC搭建了包含该附加控制器的MMC仿真模型,结果证明所提出的控制方法可以在不用增大桥臂电抗值的情况下,有效地抑制换流器的内部环流,同时不会对MMC外部输出的交流电压和电流产生负面影响。展开更多
控制系统对于柔性直流输电系统的运行性能起着至关重要的作用,因此对控制策略的研究有着重要的意义。推导了基于两相静止坐标系的模块化多电平换流器高压直流输电(modular multilevel converter-high voltage direct currenttransmissio...控制系统对于柔性直流输电系统的运行性能起着至关重要的作用,因此对控制策略的研究有着重要的意义。推导了基于两相静止坐标系的模块化多电平换流器高压直流输电(modular multilevel converter-high voltage direct currenttransmission,MMC-HVDC)系统的数学模型,再结合比例谐振(proportional resonant,PR)控制器的特性,提出了基于两相静止坐标系的MMC-HVDC系统稳态控制策略。该策略避免了两相旋转坐标系中的电流交叉耦合项,不需要前馈解耦,整个控制系统更加简单。在电磁暂态仿真软件PSCAD/EMTDC中对上述控制策略进行仿真研究,仿真结果验证了所提策略的正确性与有效性。展开更多
模块化多电平高压直流输电系统(modular multilevel converter-high voltage direct current,MMC-HVDC)通常采用基于比例积分(proportional integral,PI)的双闭环矢量控制,而PI调节存在响应速度慢、dq电流需要旋转解耦等问题。为此文章...模块化多电平高压直流输电系统(modular multilevel converter-high voltage direct current,MMC-HVDC)通常采用基于比例积分(proportional integral,PI)的双闭环矢量控制,而PI调节存在响应速度慢、dq电流需要旋转解耦等问题。为此文章提出在两相静止坐标下基于内模控制的MMCHVDC稳态控制方案。首先分析了两相静止坐标下的MMCHVDC数学模型,然后结合内模控制的特性,对电流内环的控制结构和参数进行设计,并将内模内环与PI外环结合构造出双闭环控制结构。最后在Matlab/Simulink中搭建了MMC-HVDC系统模型,对多种工况进行仿真。仿真结果表明,所设计的控制器能够有效抑制母线电压波动,并能对负荷变化快速响应,提高了系统的鲁棒性。展开更多
基金Supported by NSFC (10771101)NVAA Research Funding (NS2010197)
文摘The free Fisher information of an operator random matrix is studied. When the covariance of a random matrix is a conditional expectation, the free Fisher information of such a matrix is the double of this conditional expectation’s Watatani index.
基金supported by the National Science Foundation under grant numbers 1762133 and 1762899Any opinions,findings,and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.
文摘This paper studies the behavior of a reinforced concrete(RC)structural frame employing a tessellated structuralarchitectural(TeSA)shear wall as the lateral-load resisting element.TeSA walls are made of interlocking modules(tiles)that provide easier repairability and replaceability.A nonlinearfinite element model of a TeSA wall with tiles interlocking in one direction(1-D interlocking)is validated using test data.An RC frame from a building is modeled with a 1-D interlocking TeSA shear wall.The effects of varying rigidity of the wall-frame connections(rigid,hinged,slotted)on the lateral strength of the system and the axial load demands of the gravity-load resisting systems are evaluated.Finally,the effect of connection details on the damage of the TeSA wall is also studied.The study shows that the lateral strength of the system is the highest with a rigid connection between the wall and the system,followed by the system with hinged connections.Slotted connections,which provided no vertical coupling between the wall and the frame result in the lowest lateral strength.TeSA wall experienced“slight damage”up to a drift ratio of 2%.The system with rigid connections between the wall and the frame experienced the most damage,followed by system with hinged and slotted connections.
文摘控制系统对于柔性直流输电系统的运行性能起着至关重要的作用,因此对控制策略的研究有着重要的意义。推导了基于两相静止坐标系的模块化多电平换流器高压直流输电(modular multilevel converter-high voltage direct currenttransmission,MMC-HVDC)系统的数学模型,再结合比例谐振(proportional resonant,PR)控制器的特性,提出了基于两相静止坐标系的MMC-HVDC系统稳态控制策略。该策略避免了两相旋转坐标系中的电流交叉耦合项,不需要前馈解耦,整个控制系统更加简单。在电磁暂态仿真软件PSCAD/EMTDC中对上述控制策略进行仿真研究,仿真结果验证了所提策略的正确性与有效性。
文摘模块化多电平高压直流输电系统(modular multilevel converter-high voltage direct current,MMC-HVDC)通常采用基于比例积分(proportional integral,PI)的双闭环矢量控制,而PI调节存在响应速度慢、dq电流需要旋转解耦等问题。为此文章提出在两相静止坐标下基于内模控制的MMCHVDC稳态控制方案。首先分析了两相静止坐标下的MMCHVDC数学模型,然后结合内模控制的特性,对电流内环的控制结构和参数进行设计,并将内模内环与PI外环结合构造出双闭环控制结构。最后在Matlab/Simulink中搭建了MMC-HVDC系统模型,对多种工况进行仿真。仿真结果表明,所设计的控制器能够有效抑制母线电压波动,并能对负荷变化快速响应,提高了系统的鲁棒性。
