检索结果-南通市图书馆

Chinese Physics B 2012年第12期21卷 161-167页

作者：王申全冯健赵青 College of Information Science and engineering Northeastern University department of electrical and Computer engineering University of Alberta

In this paper, the problem of delay-distribution-dependent stability is investigated for continuous-time recurrent neural networks （CRNNs） with stochastic delay. Different from the common assumptions on time delays, it is assumed that the probability distribution of the delay taking values in some intervals is known a priori. By making full use of the information concerning the probability distribution of the delay and by using a tighter bounding technique （the reciprocally convex combination method）, less conservative asymptotic mean-square stable sufficient conditions are derived in terms of linear matrix inequalities （LMIs）. Two numerical examples show that our results are better than the existing ones.

关键词： recurrent neural networks stochastic delay mean-square stability linear matrix inequal- ity

ON COMPLEXITY OF POWER SYSTEMS

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2003年第3期16卷 391-403页

作者： MAJin CHENGDaizhan HONGYiguang departmentofelectricalengineering TsinghuaUniversityBeijing100084China InstituteofSystemsScience AcademyofMathematicsandSystemsSciencesChineseAcademyofSciencesBeijing100080China

The power system is a classical example of complex systems. In this paper it is shown that the power industry in china is facing a tremendous challenge. The complexity in power systems is investigated as follows. First, the cascade failure in power systems is analyzed, and compared with sand-pile model. Next, we show that the agent-based modelling is a proper way for power network. Mathematically, the geometric dynamics and differential inclusion are useful tools for the stability analysis of large scale power systems. As for power market, the game theory and generalized control system model are proposed. For a complex power system, an evolutive model may be more accurate in description and analysis. Finally, certain newly developed numerical methods in the power system computation are introduced. Overall, we are convinced that the theorem of complexity, combined with modern control theory, may be the right way to answer the challenges faced by the power industry in china.

关键词： power system cascade failure diagnosis agent-based modelling complexadaptive system stabilization

A Modified General Cayley Transformation for The Calculation of critical eigenvalues of large-scale power systems with DAE models

在线全文

学校读者我要写书评

暂无评论

A Modified General Cayley Transformation for The Calculation...

2011 Chinese Control and Decision Conference（CCDC）

作者： Kefei Wang is with the department of electrical engineering Tsinghua university china.Feng Liu was with Tsinghua University,china,He is now with the department of electrical engineering De Zhang is with the electrical engineering department,Tsinghua University,Shengwei Mei is currently a Professor of the department of electrical engineering,Tsinghua University.Guangyu He is a Professor of the department of electrical engineering,Tsinghua University.

The computation of critical eigenvalues of a large-scale matrix in an efficient manner is challenging for small-signal stability analysis of power *** the generalized Cayley transformation has been used extensively for calculating the critical eigenvalues,this approach breaks the sparsity of augmented state matrix during the transformation,and subsequently degrades the computation *** this paper,a modified generalized Cayley transformation is proposed to map the critical eigenvalues to the ones with the largest *** biggest advantage of this method is that the proposed transformation can preserve the sparsity of the augmented state matrix,resulting in better performance,convergence and robustness,as compared to the conventional generalized Cayley transformation method.A rigorous proof is presented to show the accuracy and the effectiveness of the proposed *** experiments are tested on both the IEEE 118-bus system and the Hainan power grid to illustrate the validity of the proposed method.

关键词： critical eigenvalues modified generalized Cayley transformation augmented state matrix.

Study on magnetism of Pr_(0.45)(Ca_(1-x)Sr_x)_(0.55) MnO_3 samples

在线全文

cnki会议

学校读者我要写书评

暂无评论

Rare Metals 2011年第6期30卷 595-601页

作者： TANG Yonggang WANG Guiying YANG Gang MAO Qiang PENG Zhensheng Cultivating Base of Anhui Key Laboratory of Spintronics and Nano-materials Research Suzhou 234000 China department of electrical and Electromc Engmeertng Suzhou University Suzhou 234000 China Hefei National Laboratory for Microscopic Matter Sciences University of Science and Technology of China Hefei 230026 China

The polycrystalline samples of Pro.45（Ca1-xSrx）0.55MnO3 （x = 0.0, 0.2, 0.4, 0.6） were prepared by solid-state reaction. Influence of Sr2＋ substitution for Ca2＋ at A site on magnetism was studied through the measurements of X-ray diffraction （XRD） spectrum, the magnetization-temperature （M-T） curves and electron spin resonance （ESR） curves. The results show that the magnetism strengthens and charge ordering weakens gradually with the increase of Sr2＋ substitution amount, respectively. The transition of paramagnetism（PM）-antiferromagnetism（AFM） occurs below the transition temperature of charge ordering （Tco）, and there is tittle ferromagnetic phase in the antiferromagnetic background at the lower temperature, which results in complex magnetic phases of the samples. Ferromagnetic clusters appear and grow larger with the increase of substitution amount./n addition, the reentrant spin-glass behavior appears at about 41 K. The magnetism phenomenon of the samples is mainly due to the competition between double exchange and Jahn-Teller coupling. The Jahn-Teller coupling becomes weak, and the double exchange wins the advantage in the competition with the increase of substitution amount, which leads to the magnetism variation of the system.

关键词： magnetism charge ordering Sr2+ substitution reentrant spin-glass state

SR Torque Ripple Control Based on Power Spectrum Evaluation of Magnetic Flux Density of Air Gap

在线全文

学校读者我要写书评

暂无评论

SR Torque Ripple Control Based on Power Spectrum Evaluation ...

2005国际电机与系统学术会议

作者： Guangzhao Cui Xianghong Cao Hua Zhang department of Cotrol Science and engineering Huazhong University of Science and Technology Wuhan 430074 china College of electrical and Information engineering Zhengzhou Institute of Light Industry Zhengzhou 450002 china department of electrical engineering Southeast University Nanjing 210096 china

＜正＞ This paper has introduced the SR motor torque ripple control scheme based on power spectrum evaluation of magnetic flux density in air gap. We analyze the feasibility of its realization theoretically and give s...

关键词：

The fault tolerant control on a dual-channel brushless DC motor servo system

在线全文

cnki会议

学校读者我要写书评

暂无评论

The fault tolerant control on a dual-channel brushless DC mo...

11th International Conference on electrical Machines and Systems

作者： Dong Huifen~(1*) Zhou Yuanjun~2 Lin Shengjun~3 1 department of Aeronautic electrical engineering Civil Aviation University of china Tianjin china 2 department of electrical engineering Beihang University Beijing china 3 Tangshan Radio and TV University Tangshan china

＜正＞The brushless DC motor with two sets of control channels is presented in the paper,which will be used in an Electro-Mechanical Actuation（EMA）of the next generation More Electric-Aircraft（EMA）.Either of the channels is failure the motor will work in the single channel mode,***-tolerant operation *** control system needs to resolve the problems of current balance,load disturbance,and structure *** to these,a three-loop integral-fuzzy-sliding control strategy is adopted,and then the system has more robustness to parameter variations and external load *** control method of the parameters fault-tolerant rebuilding is selected in the fault tolerance operation *** simulation results show that if one channel is failure the transition time of reverting to steady operation is shorten, and steady error does not exist in the fault-tolerant operation mode,the excellent fault-tolerant control performance is attained.

关键词：

Study of Protection of Transformer from Very Fast Transient Over-voltage in 750kV GIS

在线全文

cnki会议

学校读者我要写书评

暂无评论

Study of Protection of Transformer from Very Fast Transient ...

2005国际电机与系统学术会议

作者： Q. Liu School of electrical engineering, Xi’an Jiaotong University, Xi’an 710049, china department of electrical and Control engineering, Xi’an University of Science & Tecnology, Xi’an 710054, china

Gas Insulated Switchgears, also called Gas Insulated Substation, is applied to power system widely. Running experiences have shown that switching operations will generate Very Fast Transient Over-voltage, which has steep front and is followed by high frequency oscillations. VFTO spreads out of GIS and endangers the equipments connected to GIS. The transformer is the main casualty of VFTO. In this paper a 750kV GIS system has been set up. VFTO at the transformer terminal of different running modes have been calculated using Electro-Magnetic Transient Program (EMTP). This paper has studied the protective effect of shunt resistor of the switches, MOA and R-C surge sup-presser. From a large amount of simulated calculations by Electro-Magnetic Transient Program, it can be found that the shunt resistors could accelerate the attenuation of over-voltages, so the peak and gradient reduce greatly. MOA only has effect on the peak value, whereas has no effect on the gradient. R-C surge suppresser not only could limit the peak of VFTO, but also could reduce its gradient. The effect of R-C surge suppresser is better than MOA, if the values of the resistor and the capacitor are selected suitably.

关键词：

在线全文

cnki会议

学校读者我要写书评

暂无评论

用B样条有限元法解轴对称谐振腔问题

微波学报 1996年第2期12卷 96-102页

作者：李融林倪光正俞集辉浙江大学电机系杭州310027 重庆大学电气工程系重庆630044

本文利用以双二次B样条函数为基函数的B样条有限元法求解轴对称谐振腔问题.文中首先建立了圆柱坐标系中的B样条有限元法方程,然后将方法扩展到球坐标系中以避免计算球类谐振腔问题所引起的剖分误差,最后通过对圆柱谐振腔、电子加速腔和... 详细信息

本文利用以双二次B样条函数为基函数的B样条有限元法求解轴对称谐振腔问题.文中首先建立了圆柱坐标系中的B样条有限元法方程,然后将方法扩展到球坐标系中以避免计算球类谐振腔问题所引起的剖分误差,最后通过对圆柱谐振腔、电子加速腔和球谐振腔的计算分析表明此方法的特点及实用性.

关键词：谐振腔 B样条有限元

Excitation Control Based Energy-Shaping with Direct Mechanical Damping Injection for Transient Stability Improvement of Power Systems

在线全文

学校读者我要写书评

暂无评论

Excitation Control Based Energy-Shaping with Direct Mechanic...

第25届中国控制会议

作者： Jiao Xiaohong,Sun Yuanzhang,Shen Tielong Institute of electrical engineering, Yanshan University,Qinhuangdao,066004 ,china department of electrical engineering,Tsinghua University,Beijing, 100084,china department of Mechanical engineering,Sophia University,Tokyo, 102-8554,Japan

＜正＞In this paper, a novel energy-shaping design method is provided for excitation controller of power systems, which is carried out by directly injecting the compensation damping into the mechanical damping. This design method utilizes the transient energy function with the physical properties of power system,and the adjusted parameters of the designed controller have directly corresponding relation to the physical meaning of the mechanical damping and electrical damping of power system. In addition,to further enhance the transient stability,considering the possible variation in the transmission line and uncertainties in physical parameters, an adaptive excitation controller is also designed by employing the direct mechanical damping injection. It is shown that the proposed excitation controller can make the system have better dynamic properties and large stability margin even in the case with the permanent fault on transmission line and the turbine failure. And,for illustrating the effectiveness of the proposed controller, the simulation comparison results with the traditional energy-shaping approach are presented.

关键词： Direct mechanical damping injection energy-shaping excitation control transient stability power systems

Computation of SVC based on Instantaneous Reactive Power Theory

在线全文

cnki会议

学校读者我要写书评

暂无评论

Computation of SVC based on Instantaneous Reactive Power The...

2010 The 3rd International Conference on Power Electronics and Intelligent Transportation System (PEITS 2010)

作者： Meng Qingbo department of electrical engineering,Zhengzhou Railway Vocational and Technical College Zhengzhou,Henan Province,china Zhang Zhijun department of electrical engineering,Zhengzhou Railway Vocational and Technical College Zhengzhou,Henan Province,china

The paper presents the concept of Flexible AC Transmission System and Static Var *** the example of SVC for TCR+FC type,the author expounds the elements and basic principles of the SVC,proposes the controller's *** on instantaneous reactive power theory,the paper ascertains the algorithm of compensation admittance and trigger ***,changing the trigger angle of thyristor can change the electrical admittance of SVC,change the fundamental current of system and implement the reactive power compensation *** conclusion,the paper analyses the control performance of the algorithm on accuracy and real-time.

关键词： SVC TCR+FC reactive power compensation instantaneous reactive power theory,algorithm