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1.
准同步采样及其在常用电工参数数字化测量中的应用   总被引:4,自引:0,他引:4  
王石记  司锡才 《应用科技》2003,30(12):10-12
介绍了一种新的采样算法,即准同步采样,其采样周期不要求与信号周期严格同步.并将准同步采样算法应用于电工参数数字化测量中,具有良好的效果,与同步采样具有相当的准确度.计算的精确度和AD的位数有关,AD位数越高,计算也就越精确,通常,若AD的位数为16位,在工程中测量的精度可达万分之二.先介绍了准同步算法的理论依据,然后介绍了准同步系数的推导,最后介绍了如何在DSP中实现准同步算法.  相似文献   

2.
在非同步采样情况下快速傅立叶变化存在较大的误差,特别是相位的误差,无法直接用于电力系统谐波分析.为了减小非同步采样对快速傅立叶变换的影响,提高电力系统中的谐波分析精度,文中通过加窗和插值对原算法进行了改进.仿真结果表明,改进后的算法在非同步采样时,分析精度有显著提高.  相似文献   

3.
提高介质损耗因数监测准确度的算法   总被引:5,自引:0,他引:5  
为解决在电气设备介质损耗因数的计算中必须严格满足同步采样条件和计算分辨率低的问题,基于Hilbert变换和复三角函数运算,提出了一种提高介质损耗因数监测准确度的数字化算法,并给出了算法的理论基础。仿真结果表明:该算法在电网频率存在波动以及采样数据长度为非整数周期等情况时具有良好的应用特性,较好地解决了实际信号量测中存在的非同步采样问题。该算法对电网电压中谐波含量的存在并不敏感,当谐波含量在10%以下时,可获得小于1%的计算准确度。  相似文献   

4.
离散傅立叶变换(DFT)在数字信号处理、数字图象处理等许多领域起着重要作用,九长度DFT的快速计算是任意长度DFT快速算法的基础及重要组成部分,传统的素数长度DFT快速算法效率较低,且具有程序过于复杂,子进程调度较多等许多不利因素,很难在问题中得到应用,本文采用了一种傅里叶技术--算术傅立叶变换(AFT)来计算DFT〈该方法乘法计算量仅O(N),当用于计算素数长度DFT时,其效率比传统的方法高,一  相似文献   

5.
在非同步采样以及非整数周期截断情况下,快速傅里叶变换会产生频谱泄露和栅栏效应,使计算结果存在较大误差,无法得到准确参数。常用窗函数固定的旁瓣性能制约了已有加窗插值算法的误差修正效果。而凯赛(Kaiser)窗的主旁瓣高度之间的比重可依据需要自由选择,其主旁瓣能量的比例也近乎最大。文中提出基于Kaiser窗的三谱线插值FFT的电力谐波分析方法,推导了基波以及各次谐波的幅值、频率和初相位的插值修正公式。仿真结果表明,所提算法设计灵活且易于实现,在基波频率波动以及白噪声干扰下都有较高的谐波参数估计准确度,验证算法能够有效消除泄露和栅栏效应的影响,提高了谐波分析的准确性。  相似文献   

6.
通过分析周期信号的傅里叶级数和傅里叶变换的关系,为谐波分析提供理论依据。由于存在频谱泄露和栅栏效应,使用快速傅里叶变换(FFT)进行谐波分析时计算精度不高。为此,本文提出采用频域采样点数等于离散信号长度的离散傅里叶变换(DFT)进行谐波分析,可以有效的减小频谱泄露和栅栏效应带来的影响。通过模拟分析,验证了相比于FFT算法,该算法具有较高的计算精度。最后,基于该算法,使用MATLAB GUI制作了一款具有界面友好且便于数据处理的谐波分析软件,其中包含误差计算模块。利用该软件对多个信号进行谐波分析并计算误差,结果表明,误差的均方差和标准差均较小,由此进一步证实该算法是有效的。  相似文献   

7.
主要讨论如何将定义在[a,b]上的满足Dirichlet条件的非周期函数f(x)展开成Fourier级数,并给出f(x)的不同的Fourier展开式  相似文献   

8.
尹引 《广东科技》2012,21(17):34-36
阐述了一种利用离散傅里叶变换,基于准同步窗相位差法实现电网频率测量的方法,并给出了算法的推演过程。实验结果表明了该方法在宽范围内仍具有很高的测量精度。该方法采样无需与信号周期完全同步,采用纯软件算法实现,降低硬件复杂度和成本,具有重要的实际工程意义。  相似文献   

9.
提出反馈系统H∞控制问题的两步结构设计方案的状态空间法,首先应用Banach空间的逼近原理,以Cesaro和的经典技术与离散Fourier变换技术,构造一个合适的逼近传递函数,它能够由快速Fourier变换算法有效地计算;然后组成一个便于计算极小值的新的Nehari扩充问题,应用状态空间法能求出H∞控制问题的近似最佳解。  相似文献   

10.
通过分析周期信号的傅里叶级数和傅里叶变换的关系,为谐波分析提供理论依据。由于存在频谱泄露和栅栏效应,使用快速傅里叶变换(FFT)进行谐波分析时计算精度不高。为此,提出采用频域采样点数等于离散信号长度的离散傅里叶变换(DFT)进行谐波分析,可以有效地减小频谱泄露和栅栏效应带来的影响。通过模拟分析,验证了相比于FFT算法,DFT具有较高的计算精度。最后,基于DFT,使用MATLAB GUI制作了一款具有界面友好且便于数据处理的谐波分析软件;其中包含误差计算模块。利用该软件对多个信号进行谐波分析并计算误差。结果表明,误差的均方差和标准差均较小,由此进一步证实DFT是有效的。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

14.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

15.
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-  相似文献   

16.
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-  相似文献   

17.
正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that  相似文献   

18.
For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the  相似文献   

19.
Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of  相似文献   

20.
<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with  相似文献   

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