Pulse-like ground motions are capable of inflicting significant damage to structures. Efficient classification of pulse-like ground motion is of great importance when performing the seismic assessment in near-fault re...Pulse-like ground motions are capable of inflicting significant damage to structures. Efficient classification of pulse-like ground motion is of great importance when performing the seismic assessment in near-fault regions. In this study, a new method for identifying the velocity pulses is proposed, based on different trends of two parameters: the short-time energy and the short-time zero crossing rate of a ground motion record. A new pulse indicator, the relative energy zero ratio(REZR), is defined to qualitatively identify pulse-like features. The threshold for pulse-like ground motions is derived and compared with two other identification methods through statistical analysis. The proposed procedure not only shows good accuracy and efficiency when identifying pulse-like ground motions but also exhibits good performance for classifying records with high-frequency noise and discontinuous pulses. The REZR method does not require a waveform formula to express and fit the potential velocity pulses;it is a purely signal-based classification method. Finally, the proposed procedure is used to evaluate the contribution of pulse-like motions to the total input energy of a seismic record, which dramatically increases the seismic damage potential.展开更多
The notions of decoupling zeros of positive discrete-time linear systems are introduced. The relationships between the decoupling zeros of standard and positive discrete-time linear systems are analyzed. It is shown t...The notions of decoupling zeros of positive discrete-time linear systems are introduced. The relationships between the decoupling zeros of standard and positive discrete-time linear systems are analyzed. It is shown that: 1) if the positive system has decoupling zeros then the corresponding standard system has also decoupling zeros, 2) the positive system may not have decoupling zeros when the corresponding standard system has decoupling zeros, 3) the positive and standard systems have the same decoupling zeros if the rank of reachability (observability) matrix is equal to the number of linearly independent monomial columns (rows) and some additional assumptions are satisfied.展开更多
文中提出一种集成可变母线的宽输入范围双有源全桥(dual active full bridge,DAB)变换器。与传统DAB变换器不同,所提变换器本质上是四开关Buck-Boost变换器与DAB变换器原边全桥进行复用,从而实现可变母线的构造与集成。通过调节可变母...文中提出一种集成可变母线的宽输入范围双有源全桥(dual active full bridge,DAB)变换器。与传统DAB变换器不同,所提变换器本质上是四开关Buck-Boost变换器与DAB变换器原边全桥进行复用,从而实现可变母线的构造与集成。通过调节可变母线的电压,可以在很宽的电压调节范围内实现电压匹配。同时辅助电感仅处理总功率的一部分并以连续导通模式工作,从而降低损耗并减小尺寸。所有开关均被证明可实现理论上的全负载范围零电压开关操作。此外,提出一种混合脉宽调制加相移调制控制策略来实现电压匹配控制并调节功率流;详细介绍其工作原理、工作特点和参数设计原则;最后,搭建一台1 k W实验室样机来验证理论分析。展开更多
提出一种基于Boost拓扑与反激拓扑有机组合思想的Boost-Flyback变换器,Boost环节与反激环节共用输入支路,使电感–变压器的漏感能量得以利用,消除了漏感损耗,并实现了开关管电压钳位,减小了开关管电压应力;Boost与反激环节的输出支路串...提出一种基于Boost拓扑与反激拓扑有机组合思想的Boost-Flyback变换器,Boost环节与反激环节共用输入支路,使电感–变压器的漏感能量得以利用,消除了漏感损耗,并实现了开关管电压钳位,减小了开关管电压应力;Boost与反激环节的输出支路串联,实现了高电压增益;Boost-Flyback变换器输入并联输出串联,进一步提高了变换器的电压增益,同时减小了输入输出电压及电流纹波。提出新拓扑的DCM-ZVS工作模式控制方法,并在开环方式下实现了输出功率的控制。详细分析拓扑的工作原理、电压增益特性及控制方法。通过230 W 30 V/380 V的实验样机验证理论分析的有效性。展开更多
基金Supported by:National Natural Science Foundation of China under Grant Nos.51378341,51427901 and 51678407National Key Research and Development Program under Grant No.2016YFC0701108
文摘Pulse-like ground motions are capable of inflicting significant damage to structures. Efficient classification of pulse-like ground motion is of great importance when performing the seismic assessment in near-fault regions. In this study, a new method for identifying the velocity pulses is proposed, based on different trends of two parameters: the short-time energy and the short-time zero crossing rate of a ground motion record. A new pulse indicator, the relative energy zero ratio(REZR), is defined to qualitatively identify pulse-like features. The threshold for pulse-like ground motions is derived and compared with two other identification methods through statistical analysis. The proposed procedure not only shows good accuracy and efficiency when identifying pulse-like ground motions but also exhibits good performance for classifying records with high-frequency noise and discontinuous pulses. The REZR method does not require a waveform formula to express and fit the potential velocity pulses;it is a purely signal-based classification method. Finally, the proposed procedure is used to evaluate the contribution of pulse-like motions to the total input energy of a seismic record, which dramatically increases the seismic damage potential.
文摘The notions of decoupling zeros of positive discrete-time linear systems are introduced. The relationships between the decoupling zeros of standard and positive discrete-time linear systems are analyzed. It is shown that: 1) if the positive system has decoupling zeros then the corresponding standard system has also decoupling zeros, 2) the positive system may not have decoupling zeros when the corresponding standard system has decoupling zeros, 3) the positive and standard systems have the same decoupling zeros if the rank of reachability (observability) matrix is equal to the number of linearly independent monomial columns (rows) and some additional assumptions are satisfied.
文摘文中提出一种集成可变母线的宽输入范围双有源全桥(dual active full bridge,DAB)变换器。与传统DAB变换器不同,所提变换器本质上是四开关Buck-Boost变换器与DAB变换器原边全桥进行复用,从而实现可变母线的构造与集成。通过调节可变母线的电压,可以在很宽的电压调节范围内实现电压匹配。同时辅助电感仅处理总功率的一部分并以连续导通模式工作,从而降低损耗并减小尺寸。所有开关均被证明可实现理论上的全负载范围零电压开关操作。此外,提出一种混合脉宽调制加相移调制控制策略来实现电压匹配控制并调节功率流;详细介绍其工作原理、工作特点和参数设计原则;最后,搭建一台1 k W实验室样机来验证理论分析。
文摘提出一种基于Boost拓扑与反激拓扑有机组合思想的Boost-Flyback变换器,Boost环节与反激环节共用输入支路,使电感–变压器的漏感能量得以利用,消除了漏感损耗,并实现了开关管电压钳位,减小了开关管电压应力;Boost与反激环节的输出支路串联,实现了高电压增益;Boost-Flyback变换器输入并联输出串联,进一步提高了变换器的电压增益,同时减小了输入输出电压及电流纹波。提出新拓扑的DCM-ZVS工作模式控制方法,并在开环方式下实现了输出功率的控制。详细分析拓扑的工作原理、电压增益特性及控制方法。通过230 W 30 V/380 V的实验样机验证理论分析的有效性。
