期刊文献+
共找到14篇文章
< 1 >
每页显示 20 50 100
基于时变相量小信号模型的逆变器并联控制系统分析与设计 被引量:14
1
作者 高范强 王平 +4 位作者 李耀华 李子欣 朱海滨 胜晓松 董贯洁 《中国电机工程学报》 EI CSCD 北大核心 2011年第33期75-84,共10页
在逆变器无线并联系统中,下垂控制器的参数会影响功率均分的动态响应和稳定性。传统的方法是利用准稳态相量的小信号模型来辅助设计下垂控制器。然而,交流信号的准稳态相量在分析动态响应较快的逆变器并联系统时会受到局限。以使用下垂... 在逆变器无线并联系统中,下垂控制器的参数会影响功率均分的动态响应和稳定性。传统的方法是利用准稳态相量的小信号模型来辅助设计下垂控制器。然而,交流信号的准稳态相量在分析动态响应较快的逆变器并联系统时会受到局限。以使用下垂控制的400 Hz逆变器并联系统为研究对象,建立该系统基于时变相量的小信号模型。理论分析表明,传统的小信号模型在设计并联系统参数时有局限性。与传统的模型相比,所建立的基于时变相量的小信号模型考虑了下垂调节的暂态过程,解释了传统模型扩大了系统参数选择范围的原因,并对并联系统的参数提供了更加精确的选择范围。仿真和实验结果验证了该小信号模型的准确性。 展开更多
关键词 时变相量 小信号模型 下垂控制 400Hz逆变 并联控制
下载PDF
基于时变相量的配电网PT铁磁谐振研究与措施分析 被引量:2
2
作者 李国成 周海全 郭维明 《山东理工大学学报(自然科学版)》 CAS 2012年第4期56-60,共5页
利用相模变换理论,建立了配电网发生绝缘放电时的故障分析模型,分析了配电网PT发生铁磁谐振的原因及稳态谐振的发生机理.根据系统的0模网络的ΔI(φL)曲线提出了加装零序PT抑制铁磁谐振的方法,以避免系统发生工频铁磁谐振.
关键词 铁磁谐振 时变相量 稳态谐振 消谐措施 0序PT
下载PDF
时变相量下基于陷波滤波算法的下垂控制方法改进
3
作者 魏卿 吕智林 +1 位作者 许柳 孟泽晨 《电测与仪表》 北大核心 2018年第13期12-18,共7页
传统下垂控制中忽略了功率测量对电压频率有差控制的重要性,功率的测量往往通过一阶低通滤波器来获得,由于低通滤波器低频极点的存在,导致带宽受到限制。因此必须在响应速度与功率纹波抑制之间做出权衡;孤岛逆变器运行系统中,下垂参数... 传统下垂控制中忽略了功率测量对电压频率有差控制的重要性,功率的测量往往通过一阶低通滤波器来获得,由于低通滤波器低频极点的存在,导致带宽受到限制。因此必须在响应速度与功率纹波抑制之间做出权衡;孤岛逆变器运行系统中,下垂参数的选取对于系统的稳定性和动态响应有着很大的影响,传统准静态相量忽略了系统中动态变化的成分,理论上稳定的控制参数可能导致实际运行系统的不稳定。基于此引入了陷波滤波算法建立了感性系统下时变相量小信号模型,给出了更为精确的参数选择范围,在分析系统动态过程的基础上解释了准静态模型下稳定区域增大的原因。陷波滤波算法改善了功率纹波抑制效果和系统响应速度,仿真和实验验证了所提出方法的合理和有效性。 展开更多
关键词 陷波滤波器 时变相量 小信号模型 下垂控制
下载PDF
基于时变相量的配电网PT过电压原因分析研究
4
作者 杜正旺 《山东大学学报(工学版)》 CAS 北大核心 2012年第2期124-129,137,共7页
在配电网中性点不接地系统中,利用相模变换理论得到系统的0模等效电路,分析了导致电压互感器(potential transformer,PT)铁磁谐振过电压发生的内在原因。基于时变相量的数学模型建立0模网络,得到系统的ΔI(φL)曲线;通过对曲线的分析,... 在配电网中性点不接地系统中,利用相模变换理论得到系统的0模等效电路,分析了导致电压互感器(potential transformer,PT)铁磁谐振过电压发生的内在原因。基于时变相量的数学模型建立0模网络,得到系统的ΔI(φL)曲线;通过对曲线的分析,可知系统中稳态谐振点的存在是导致铁磁谐振发生的主要原因;最后根据扰动的大小,基于李亚普诺夫能量函数提出了加速能量和减速能量的概念,并提出了判断系统发生稳态谐振准则——等面积法则。电力系统暂态仿真软件(alternative transient program,ATP)仿真结果验证了上述理论的正确性。此研究成果对分析配电网电压互感器(PT)烧坏事故及后续抑制铁磁谐振的研究工作提供了重要的理论依据。 展开更多
关键词 PT 铁磁谐振 过电压 时变相量
原文传递
等面积法则在铁磁谐振分析中的应用 被引量:9
5
作者 杜正旺 周海全 +2 位作者 哈恒旭 胡希同 仲崇山 《电力系统保护与控制》 EI CSCD 北大核心 2011年第7期26-31,共6页
电力系统运行经验表明,中性点不接地的电力系统中经常发生铁磁谐振现象,铁磁谐振严重影响系统的安全性、稳定和可靠性。为了有效分析电力系统中时有发生的铁磁谐振现象,将配电网系统经过相模变换将其转化0模网络,建立0模网络的数学模型... 电力系统运行经验表明,中性点不接地的电力系统中经常发生铁磁谐振现象,铁磁谐振严重影响系统的安全性、稳定和可靠性。为了有效分析电力系统中时有发生的铁磁谐振现象,将配电网系统经过相模变换将其转化0模网络,建立0模网络的数学模型。引入时变相量的概念,建立系统的时变相量数学模型,分析了系统的三个平衡点。定义了系统的稳定裕度和扰动量的计算公式,创新性地把等面积法则应用到铁磁谐振电路的分析中,并讨论了铁磁谐振的发生与故障时间有密切的关系。把对铁磁谐振的分析由以往的定性分析上升到定量分析,并通过ATP仿真验证了等面积法则在铁磁谐振中的实效性。 展开更多
关键词 铁磁谐振 平衡点 等面积法则 时变相量 稳定裕度 扰动
下载PDF
准比例谐振控制的单相逆变器并联控制技术 被引量:1
6
作者 周锦荣 王辉 周小方 《青岛科技大学学报(自然科学版)》 CAS 2015年第2期199-205,共7页
针对传统的逆变器控制策略对交流信号跟踪出现的偏差问题,在准比例谐振控制器的双环控制基础上,提出输出有功功率和无功功率与输出电压相位和幅度解耦后的新型下垂控制算法。应用时变相量法建立并联系统的小信号模型,分析下垂系数的变... 针对传统的逆变器控制策略对交流信号跟踪出现的偏差问题,在准比例谐振控制器的双环控制基础上,提出输出有功功率和无功功率与输出电压相位和幅度解耦后的新型下垂控制算法。应用时变相量法建立并联系统的小信号模型,分析下垂系数的变化对系统稳定性和动态性能的影响。仿真实验结果表明,利用准比例谐振控制器和新型下垂控制策略能有效地实现单相逆变器并联控制。 展开更多
关键词 准比例谐振控制器 双闭环并联控制 下垂控制算法 时变相量 小信号模型
下载PDF
Airborne Pollen Grains Of Afyon, Turkey 被引量:3
7
作者 Adem BICAKCI 1, Süheyla ERGUN 2, Sevcan TATLIDIL 1, Hulusi MALYER 1, Sabri ?ZYURT 2, Ahmet AKKAYA 3, Nihat SAPAN 5 Department of Biology, Faculty of Science, University of Uludag, Bursa, Turkey 2. Department of Biology, Faculty of Science, University of Afyon Kocatepe, Afyon Turkey +1 位作者 3. Department of Pulmonology, Faculty of Medicine, University of Süleyman Demirel, Isparta, Turkey 4. Division of Pediatric Allergy, Faculty of Medicine, University of Uludag, Bursa, Turkey) 《Acta Botanica Sinica》 CSCD 2002年第11期1371-1375,共5页
The airborne pollen grains of Afyon have been studied for a two_year period (1999-2000) with a Durham sampler. A total of 14 367 pollen grains belonging to 40 taxa have been identified and recorded with some unidentif... The airborne pollen grains of Afyon have been studied for a two_year period (1999-2000) with a Durham sampler. A total of 14 367 pollen grains belonging to 40 taxa have been identified and recorded with some unidentified ones. Of them, 6 732 were identified in 1999 and 7 635 in 2000. Of the total pollen grains, 69.67% were arboreal, 26.64% non_arboreal and 3.68 % unidentified. The majority of the investigated pollen grains were from Pinus, Gramineae, Cupressaceae, Platanus , Chenopodiaceae/Amaranthaceae, Quercus, Ailanthus, Moraceae, Juglans , Salix, Cedrus and Rosaceae. The highest level of pollen grains was in May. 展开更多
关键词 TURKEY Afyon pollen calendar pollen grains
下载PDF
Effect of the Interference Instant of Zeolite HY Catalyst on the Pyrolysis of Pubescens 被引量:3
8
作者 刘文武 胡常伟 +2 位作者 杨宇 祝良芳 重冬梅 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2010年第2期351-354,共4页
A laboratory reactor was designed to test the effect of the interference instant of HY on the pyrolysis of pubescens.The time instant for intermediate species from pyrolysis to contact HY was controlled by varying the... A laboratory reactor was designed to test the effect of the interference instant of HY on the pyrolysis of pubescens.The time instant for intermediate species from pyrolysis to contact HY was controlled by varying the position of the catalyst bed relative to the pyrolytic cell.It was found that the effect of the interference instant was significant on the variation of different intermediate species,and the yield and quality of the products.The results also showed that,with the increase in the distance between the pyrolytic cell and the catalyst bed,the yield of liquid and relative content of the organics such as aldehyde,phenols,etc.,decreased,while the yield of residue and relative content of acetic acid increased.The deoxygenation of the intermediate species was favored when the catalyst exerted its performance on them immediately after their formation. 展开更多
关键词 zeolite HY catalytic pyrolysis pubescens acetic acid intermediate conversion
下载PDF
Evolution of distribution and content of water in cement paste by low field nuclear magnetic resonance 被引量:11
9
作者 佘安明 姚武 袁万城 《Journal of Central South University》 SCIE EI CAS 2013年第4期1109-1114,共6页
The low field nuclear magnetic resonance (NMR), as a nondestructive and noninvasive technique, was employed to investigate the water distribution and content in cement paste with different water-to-cement ratio (w/c r... The low field nuclear magnetic resonance (NMR), as a nondestructive and noninvasive technique, was employed to investigate the water distribution and content in cement paste with different water-to-cement ratio (w/c ratio) during early and later hydration stages. From the water distribution spectrum deduced from relaxation time distribution in paste, it is suggested that the water fills in the capillary pores at initial period, and then diffuses to the mesopores and gel pores in hydration products with the hydration proceeding. The decrease of peak area in water distribution spectrum reflects the transformation from physically bound water to chemically bound water. In addition, based on the connection between relaxation time and pore size, the relative content changes of water in various states and constrained in different types of pores were also measured. The results demonstrate that it is influenced by the formation of pore system and the original water-to-cement ratio in the paste. Consequently, the relative content of capillary water is dropped to less than 2% in the paste with low w/c ratio of 0.3 when being hydrated for 1 d, while the contents are still 16% and 36% in the pastes with w/c ratios of 0.4 and 0.5, respectively. 展开更多
关键词 cement water DISTRIBUTION water-to-cement ratio PORE nuclear magnetic resonance
下载PDF
Phase Space Prediction of Chaotic Time Series with Nu-Support Vector Machine Regression 被引量:1
10
作者 YEMei-Ying WANGXiao-Dong 《Communications in Theoretical Physics》 SCIE CAS CSCD 2005年第1期102-106,共5页
A new class of support vector machine, nil-support vector machine, isdiscussed which can handle both classification and regression. We focus on nu-support vector machineregression and use it for phase space prediction... A new class of support vector machine, nil-support vector machine, isdiscussed which can handle both classification and regression. We focus on nu-support vector machineregression and use it for phase space prediction of chaotic time series. The effectiveness of themethod is demonstrated by applying it to the Henon map. This study also compares nu-support vectormachine with back propagation (BP) networks in order to better evaluate the performance of theproposed methods. The experimental results show that the nu-support vector machine regressionobtains lower root mean squared error than the BP networks and provides an accurate chaotic timeseries prediction. These results can be attributable to the fact that nu-support vector machineimplements the structural risk minimization principle and this leads to better generalization thanthe BP networks. 展开更多
关键词 chaotic time series phase space PREDICTION support vector machines
下载PDF
The identification algorithm for commensurate order linear time-invariant fractional systems
11
作者 王振滨 曹广益 朱新坚 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2005年第5期576-580,共5页
An efficient identification algorithm is given for commensurate order linear time-invariant fractional systems. This algorithm can identify not only model coefficients of the system, but also its differential order at... An efficient identification algorithm is given for commensurate order linear time-invariant fractional systems. This algorithm can identify not only model coefficients of the system, but also its differential order at the same time. The basic idea is to change the system matrix into a diagonal one through basis transformation. This makes it possible to turn the system’s input-output relationships into the summation of several simple subsystems, and after the identification of these subsystems, the whole identification system is obtained which is algebraically equivalent to the former system. Finally an identification example verifies the effectiveness of the method previously mentioned. 展开更多
关键词 fractional systems COMMENSURATE linear time-invariant state-space representation system identification
下载PDF
Wavelet matrix transform for time-series similarity measurement 被引量:2
12
作者 胡志坤 徐飞 +1 位作者 桂卫华 阳春华 《Journal of Central South University》 SCIE EI CAS 2009年第5期802-806,共5页
A time-series similarity measurement method based on wavelet and matrix transform was proposed,and its anti-noise ability,sensitivity and accuracy were discussed. The time-series sequences were compressed into wavelet... A time-series similarity measurement method based on wavelet and matrix transform was proposed,and its anti-noise ability,sensitivity and accuracy were discussed. The time-series sequences were compressed into wavelet subspace,and sample feature vector and orthogonal basics of sample time-series sequences were obtained by K-L transform. Then the inner product transform was carried out to project analyzed time-series sequence into orthogonal basics to gain analyzed feature vectors. The similarity was calculated between sample feature vector and analyzed feature vector by the Euclid distance. Taking fault wave of power electronic devices for example,the experimental results show that the proposed method has low dimension of feature vector,the anti-noise ability of proposed method is 30 times as large as that of plain wavelet method,the sensitivity of proposed method is 1/3 as large as that of plain wavelet method,and the accuracy of proposed method is higher than that of the wavelet singular value decomposition method. The proposed method can be applied in similarity matching and indexing for lager time series databases. 展开更多
关键词 wavelet transform singular value decomposition inner product transform time-series similarity
下载PDF
OPTIMAL ALLOCATION FOR ESTIMATING THE CORRELATION COEFFICIENT OF MORGENSTERN TYPE BIVARIATE EXPONENTIAL DISTRIBUTION BY RANKED SET SAMPLING WITH CONCOMITANT VARIABLE 被引量:1
13
作者 XIE Minyu XIONG Ming WU Ming 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2013年第2期249-260,共12页
Ranked set sample is applicable whenever ranking of a set of sample units can be done easily by a judgement method of the study variable or of the auxiliary variable. This paper considers ranked set sample based on th... Ranked set sample is applicable whenever ranking of a set of sample units can be done easily by a judgement method of the study variable or of the auxiliary variable. This paper considers ranked set sample based on the auxiliary variable X which is correlated with the study variable Y, where (X, Y) follows Morgenstern type bivariate exponential distribution. The authors discuss the optional allocation for unbiased estimators of the correlation coefficient p of the random variables X and Y when the auxiliary variable X is used for ranking the sample units and the study variable Y is measured for estimating the correlation coefficient. This paper first gives a class of unbiased estimators of p when the mean 0 of the study variable Y is known and obtains an essentially complete subclass of this class. Further, the optimal allocation of the unbiased estimators is found in this subclass and is proved to be Bayes, admissible, and minimax. Finally, the unbiased estimator of p under the optimal allocation in the case of known θ is reformed for estimating p in the case of unknown θ, and the reformed estimator is shown to be strongly consistent. 展开更多
关键词 Concomitants of order statistic Morgenstern type bivariate exponential distribution optimal allocation ranked set sample unbiased estimator.
原文传递
New exact solutions of the reaction-diffusion equation with variable coefficients via the mathematical computation
14
作者 Jin Hyuk Choi Hyunsoo Kim 《International Journal of Biomathematics》 SCIE 2018年第4期111-124,共14页
In this paper, we construct new exact solutions of the reaction-diffusion equation with time dependent variable coefficients by employing the mathematical computation via the Painleve test. We describe the behaviors a... In this paper, we construct new exact solutions of the reaction-diffusion equation with time dependent variable coefficients by employing the mathematical computation via the Painleve test. We describe the behaviors and their interactions of the obtained solutions under certain constraints and various variable coefficients. 展开更多
关键词 Painleve test wave transformation exact solution mathematical computa-tion.
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部