电力系统谐波分析的ANN算法及其误差分析

介绍了电网谐波实时分析的ANN算法，并对未知谐波干扰下采用该方法进行谐波分析的误差做出了分析。最后还针对这种误差提出了对测量数据进行周期处理的方法，以提高学习稳定时的测量精度。     

周期信号的谐波分析述评

叙述了周期信号谐波分析的基本原理及基本过程。综述了近年来谐波分析的几种典型方法；同步采样法；准同步采样法；采样补偿法，讨论了各种方法的优缺点，对量化误差给谐波分析带来的误差影响结论也进行了介绍。对谐波分析中容易忽略的几个基本问题进行了归纳和总结：1）采集信号整周期问题；2）应用FFT时的信号点数问题；3）谐波分析过程的补偿及迭代收敛性问题，同时，介绍了一种非常简便易行的直接进行谐波分析的典型过程-软件同步法过程，并用一个实测实验结果验证了其效果。     

大型经纬仪轴系晃动的傅里叶谐波分析方法

详细介绍了用傅用叶谐波分析方法对大型经纬仪的水平轴晃动误差和生趣轴晃动误差的来源进行分析并采取改进措施，以及对经纬仪测角误差的修正方法。     

高精度电网功率因数测量加权插值FFT优化算法

本文对电网功率因数测量的谐波分析方法进行了讨论。针对误差产生的原因,对窗函数的选择进行了分析;采用双峰插值算法,减少了相位测量误差;推导了采样4周期512点,而实际只进行128点的FFT优化算法,从而降低了谐波法测量功率因数的计算量。以上算法已应用于实际项目中,并取得了较好的效果。     

离散傅里叶变换量化效应的研究

本文研究了DFT谐波分析中A/D转换器量化效应对谐波幅度和相位分析准确度的影响,并导出了误差传递关系式;讨论了在信号、系数(三角函数)量化效应同时存在时的谐波分析误差,并利用微小标准偏差准则研究了如何根据A/D转换器的量化位数来合理选择系数的量化位数,使系数量化引起的谐波分析误差与A/D转换器量化引起的误差相比可以忽略不计,同时又使DFT的计算量最小。结果表明,系数量化位数高于信号量化位数2～4位就已足够。     

模拟数字混合乘法器矢量测量的原理及应用

首先介绍了一种矢量测量的新原理，并对该测量原理的幅度误差和相位误差进行了理论分析。然后，仿真分析了谐波分析的矢量误差，并给出了相应的实验测试结果。结果表明，相位测量的理论误差为零，幅度测量的理论误差可用修正系数消除，且使用较低位数的D／A转换器，可得到高准确度的结果。最后，给出此种矢量测量原理应用的几种方案。     

电力参数间谐波测量算法的研究

DFT的泄漏和栅栏效应不能测量电力系统的间谐波和分析电力系统谐波误差。一般通过加窗插值DFT能测量间谐波,然而需要构造窗函数使得分析及实际运行变得复杂。本文通过简单的频域变换结合多谱线插值并且给出了一种相应的算法,仿真结果表明该方法运行简单便于分析,精度高,因此为电力系统谐波分析提供了一种满意的工具。     

一种基于多重平均的谐波新算法

在多重平均谐波分析的基础上,提出了一种新的谐波分析算法,可以准确方便地计算出各次谐波的幅值和相位。通过计算机仿真和实验验证证实了该方法的准确程度,并采用蒙特卡罗实验研究了噪声的影响,得出了工程实用的结论。     

基于LabVIEW的电机数据采集系统

介绍了基于LabVIEW的电机数据采集系统的硬件组成和软件设计，提出了在LabVIEW下高速连续采集及存盘技术的实现方法，以及自动搜索基波频率的谐波分析方法，还分析了循环采样方式造成的各采样通道之间的相对相位误差产生的原因，提出采用分组采样方式减小这种误差，并给出了部分程序．最后给出了部分试验结果，证明所提方法的正确性．     

电压信号的谐波精密测量方法和实现

本文着重介绍由于目前电网中的谐波问题已经影响到了用电安全,电网谐波的监测仪器越来越多,这部分的仪器需要得到校准.通过介绍目前常用的谐波分析原理和我们实验室最近使用谐波发生源和RMM3000,3458A等仪器,编写了谐波分析软件,并且对其进行了算法优化,实现了对电压信号的谐波精密测量.     

Statistical analysis for windowed Fourier ridge algorithm in fringe pattern analysis

Based on the windowed Fourier transform, the windowed Fourier ridges (WFR) algorithm and the windowed Fourier filtering algorithm (WFF) have been developed and proven effective for fringe pattern analysis. The WFR algorithm is able to estimate local frequency and phase by assuming the phase distribution in a local area to be a quadratic polynomial. In this paper, a general and detailed statistical analysis is carried out for the WFR algorithm when an exponential phase field is disturbed by additive white Gaussian noise. Because of the bias introduced by the WFR algorithm for phase estimation, a phase compensation method is proposed for the WFR algorithm followed by statistical analysis. The mean squared errors are derived for both local frequency and phase estimates using a first-order perturbation technique. These mean square errors are compared with Cramer-Rao bounds, which shows that the WFR algorithm with phase compensation is a suboptimal estimator. The above theoretical analysis and comparison are verified by Monte Carlo simulations. Furthermore, the WFR algorithm is shown to be slightly better than the WFF algorithm for quadratic phase.     

Optimally averaging the interpolated fast fourier transform in both directions

The interpolated fast Fourier transform FFT (IpFFT) had been proposed to eliminate the picket fence effect of the fast Fourier transform. However, the modulus-based IpFFT (without windowing) is subjected to large bias in the condition of nearly coherent sampling condition. In addition, only the first and second highest spectral lines were used in most relevant references. The complex spectrum-based IpFFT is investigated. It is less sensitive to the interpolating direction error. Further, both directions of IpFFT can be averaged to decrease the estimation variance. The optimal weight required to minimise the estimation variance is established. The numerical simulation is carried out, and the results are compared with the Cramer-Rao bound.     

ZFFT与Chirp-Z变换细化选带的频谱分析对比

在细化选带频谱分析中，复调制细化方法（ZFFT）和线性调频Z变换方法（Chirp—Z变换）是常用的两种方法。通过理论分析和仿真计算，对两者在算法、特点和误差方面进行对比分析表明：对于单频率和谱线干涉不严重的多频率谐波成分，使用FFT后进行校正，或者使用CZT细化分析，均能得到高精度的频率、幅值和相位，不必使用ZFFT；对于发生严重干涉现象的密集多频率谐波成分，ZFFT通过增大细化倍数后重采样，把干涉的各频率成分分离后进行校正可获得高精度的信号参数，但CZT只是把细化分析频带局部放大，无法消除干涉影响，提高频率分辨率也无法分离出信号的真实频率成分。通过增大采样点数，减少干涉产生的误差，CZT可以获得较高精度的信号参数，但却大大增加了运算时间。     

A new approach to the Fourier analysis of periodic signals for theminimization of the phase errors

The methods used to reduce the errors in the determination of the harmonic phase of periodic signals by means of digital techniques are considered. The authors first briefly review the theory of the discrete Fourier transform (DFT) in order to discuss the genesis of the phase errors. They then give evidence that this approach has no general validity. An original method to minimize these phase errors while keeping the computation burden comparable with the of the classic FFT algorithm is proposed. The results of some experimental work done to verify the proposed method are reported, showing that the phase errors can be reduced by up to two decades with respect to those of the usual methods     

制造误差影响齿轮副啮合的接触有限元分析方法

制造误差是影响齿轮副啮合的重要因素,研究其作用机理对齿轮的减振设计具有重要意义。首先基于几种典型制造误差的结构形式提出了一般的精确建模方法,以一对渐开线直齿轮为例,利用接触有限元分析方法对啮合过程进行仿真,发现理想齿轮副和含误差齿轮副啮合过程中的角速度、动态接触力特性表现出显著差异。然后进行单项误差影响齿轮振动的机理研究,分别以齿廓误差和齿距误差为对象,利用傅里叶变换量化分析了不同加工公差等级下的单项制造误差对齿轮副动态传递误差、角加速度特性的影响规律。研究表明:所提出的建模方法可以模拟任意形式的微小量级的制造误差,并体现在接触有限元分析中。不但能够用于精细化研究制造误差对齿轮副啮合过程的影响,还可以通过量化各项啮合特性分析单项误差影响齿轮振动的作用机理,并指导齿轮的减振设计和精度设计等。     

Windowed Fourier transform for fringe pattern analysis: theoretical analyses

A windowed Fourier ridges (WFR) algorithm and a windowed Fourier filtering (WFF) algorithm have been proposed for fringe pattern analysis and have been demonstrated to be versatile and effective. Theoretical analyses of their performances are of interest. Local frequency and phase extraction errors by the WFR and WFF algorithms are analyzed in this paper. Effectiveness of the WFR and WFF algorithms will thus be theoretically proven. Consider four phase-shifted fringe patterns with local quadric phase [c(20)=c(02)=0.005 rad/(pixel)(2)], and assume that the noise in these fringe patterns have mean values of zero and standard deviations the same as the fringe amplitude. If the phase is directly obtained using the four-step phase-shifting algorithm, the phase error has a mean of zero and a standard deviation of 0.7 rad. However, when using the WFR algorithm with a window size of sigma(x)=sigma(y)=10 pixels, the local frequency extraction error has a mean of zero and a standard deviation of less than 0.01 rad/pixel and the phase extraction error in the WFR algorithm has a mean of zero and a standard deviation of about 0.02 rad. When using the WFF algorithm with the same window size, the phase extraction error has a mean of zero and a standard deviation of less than 0.04 rad and the local frequency extraction error also has a mean of zero and a standard deviation of less than 0.01 rad/pixel. Thus, an unbiased estimation with very low standard deviation is achievable for local frequencies and phase distributions through windowed Fourier transforms. Algorithms applied to different fringe patterns, different noise models, and different dimensions are discussed. The theoretical analyses are verified by numerical simulations.     

一个通用的频谱误差校正快速算法

建立通用的频谱误差数学模型;得出利用信号频域能量信息反求信号幅值、利用信号频域能量重心信息反求信号频率的频谱误差校正算法。该算法适用于加任意对称窗的情形,且速度快、精度高,其有效性得到了数值仿真的验证。     

小波变换电力谐波功率测量误差分析与抗泄漏算法研究

通过理论分析指出,在信号非同步采样条件下,基于小波变换的谐波功率测量方法存在着很大的带内泄漏.仿真表明,带内能量泄漏引起的测量误差可达5×10~(-2).针对该泄漏误差,推导了误差公式,并提出了一种基于整系数交迭窗函数的抗带内泄漏的小波变换谐波功率测量新算法.结果可知:抗带内泄漏功率测量新算法的相对误差小于1.2×10~(-4),测量准确度比传统的小波变换谐波功率测量算法提高了两个数量级.     

Error analysis of digital phase measurement of distorted waves

An analysis of errors associated with the digital measurement of phase angle between two signals, one of which may be distorted by a harmonic, is presented. All the results were found by running a simulation program on a VAX 11/780 computer. The results are very useful for the users of the phase meters. This technique may introduce large errors for some particular types of input waves. The main purpose of this work is to explain how large the error could be under certain conditions on the input waves