基于数据增强的电流互感器频率变化特征提取

电流互感器在受到信息缺失和噪声的影响时会导致特征无法被精准提取,这里提出了基于数据增强的电流互感器频率变化特征提取研究方法。采集电流互感器输入信号及输出信号样本,高斯混合模型(GMM)-生成式对抗网络(GAN)模型将GMM与GAN相结合,增强所采集数据样本,使数据样本集具有较高多样性;基于增强后的数据样本集获取输入信号的自相关函数及输入、输出信号的互相关函数,应用加窗插值快速傅里叶变换(FFT)计算自相关函数及互相关函数,获取输入信号的自功率谱及输出输入信号的互功率谱,利用自功率谱及互功率谱获取电流互感器频率响应函数即频率变化特征,防止部分数据未被提取。实验结果表明,所提方法可精准提取电流互感器的频率变化特征,且噪声为10 dB及20 dB时的频率变化特征提取相对误差低于0.05%。     

频率响应分析法在诊断油纸绝缘互感器整体含水量方面的应用

为寻求一种有效评估互感器整体含水量的无损诊断方法并获取相应特征量,对4支不同绝缘状态的电流互感器进行频率响应试验,试验电压为200V,电压频率为1mHz~1kHz。试验结果表明:含水量高的电流互感器频谱曲线整体呈现凸函数特性,且随着含水量增加,幅值大幅抬升但曲线形状基本不变;含水量较低的电流互感器频谱曲线整体呈现凸函数特性,且随着含水量增加,幅值增加较小;频率小于1Hz时,复电容实部随频率的降低而增大且含水量越高增幅越大;频率大于1Hz时,复电容实部基本不随含水量和频率变化;复电容虚部随电场频率降低而大幅增加,随含水量增加而变大。     

一种新型搜索电机转子频率的方法

针对高压变频调速系统,提出了一种新型的"飞车起动"控制算法。该算法无需配置电压互感器及转速传感器,仅由定子电流幅值的大小即可快速搜索出旋转电机的转速。为了实现该功能,推导了维持定子电流恒定时,定子电压与输出频率、电机转速之间的稳态数学表达式,证明了定子电流与电机估计转速之间具有单调递增的函数关系,并获得了该函数关系成立的限制条件。在此基础上,在搜频过程中,算法根据设定的规律动态改变变频器的输出频率,提高了电机转子频率搜索的快速性和准确性。仿真结果验证了理论分析的正确性和所提方法的有效性。     

基于断面信息的多区域互联系统频率响应模型参数估计方法

针对计及新能源惯量和频率支撑的多区域互联系统等效频率响应模型的参数估计问题,该文提出了一种基于联络线断面信息的简单方法,用以估计各区域等值机组与新能源场站的频率响应特性。首先基于区域内新能源场站至并网点联络线的断面有功功率与频率信息,估计区域内新能源场站虚拟惯量与有功-频率下垂系数。在此基础上,基于区域间联络线断面在惯量响应和一次调频时间尺度上的频率与传输有功功率数据,估计区域等值机组惯量与一次调频参数。然后结合各区域参数估计结果,构建完整系统频率响应模型。最后通过在PSCAD/EMTDC中搭建标准IEEE 5区68节点算例验证了所提频率响应模型及其参数估计方法的有效性。此外,在含50k W的柴油发电机和50k W基于虚拟同步控制技术的储能变流器的实际微电网系统中,进一步验证了所提估计方法的有效性。     

独立逆变器无电流互感器控制研究

针对独立逆变器的应用,提出了一种采用估计电容电流来实现无电流互感器多环控制的逆变器方案,分析了各个控制环原理,建立了控制器的数学模型,并着重通过模型和仿真讨论了在估计电容电流中由电容参数偏差对系统动静态特性的影响,最后给出了几种电容参数偏差下无电流互感器控制逆变器的实验结果.其结果证明了该控制方法的有效性.     

相关函数在误差测量中的应用分析

从相关函数的基本原理出发,分析了频率偏移对信号测量准确度的影响。理论分析和仿真实验结果表明,在信号频率偏离额定基波频率时,用相关函数法计算引起的测量误差与频率偏差的大小、信号的初始相位和信号间的相位差有关。基于这个误差特性,将相关函数测量法引入到电流互感器校验中,可以分析当互感器的精度满足准确级要求时,由数字相关法带来的测量误差是微小的。     

可控串补等值阻抗的计算方法研究

利用小信号分析法 ,对可控串补的频率响应特性进行了研究。对可控串补输入小信号电流 ,求取可控串补中各电压电流 ,并利用傅里叶分析方法求得各信号的相应频率分量 ,进而求得可控串补的频率响应特性。该研究对可控串补系统的次同步谐振以及其他相关的谐波研究有重要意义 ,分析方法对其他FACTS元件的研究有借鉴作用。EMTP仿真验证了本文方法的有效性。     

适用于非同步采样的相位差准确测量方法

提出了一种基于相关原理的电信号相位差准确测量方法,在同步采样条件下,对电压、电流信号作归一化处理后得到的2信号的互相关函数在初始时刻的值直接反映了它们之间的相位差。电信号频率发生波动时,同步采样变成非同步采样,根据相关函数的原理式进行推导得到改进的相位差测量算法。并对其在实际测量中的主要不确定源进行了分析,定量地给出它们对改进算法测量质量的影响程度。该方法可同时测量出相位差和信号的频率,具有较高的准确度, 适用于同步采样和非同步采样两种情况。实验及仿真结果均验证了该方法的有效性。     

以LabVIEW为开发平台的电子式互感器校验仪设计

鉴于传统的电流互感器测试方法已经不适于校验新型的电流互感器,依据IEC标准和误差分析理论,研制出了一种以LabVIEW为开发平台的新型电子式电流互感器校验仪。该校验仪能准确测定出电子式电流互感器的比值误差、相角误差、频率、谐波等性能指标,具有方便、灵活、易于拓展功能等优点。采用离散傅里叶变换加窗插值算法可快速准确地测量波动频率,采用频率跟踪的方法减小了电网信号频率波动对校验结果的影响,大大提高了互感器校验的精度。     

直流光纤电流互感器宽频测量特性

针对高压直流输电系统直流电流测量装置宽频测量的实际需求,结合国家标准要求,研究了直流光纤电流互感器的频率响应和阶跃响应特性及性能改善方法。考虑反馈延时、调制器驱动电路二阶频响特性及滑动平均输出滤波器的影响,建立了直流光纤电流互感器高阶离散域数学模型,分析了互感器的频率响应和阶跃响应特性,确定了闭环信号检测系统的前向增益和输出滤波器的阶数是影响互感器宽频测量性能的关键因素。通过仿真计算,优化配置前向增益和滤波器阶数,可在抑制超调的同时,提高互感器的宽频电流测量准确度及带宽。搭建了直流光纤电流互感器频率响应测试平台,提出了阶跃响应等效测试方法。实验结果表明样机的宽频测量性能可满足GB/T26216.1—2010的要求。     

A correlation based method for discrimination between inrush and short circuit currents in differential protection of power transformer using Discrete Wavelet Transform: Theory,simulation and experimental validation

This paper presents a new method for discrimination between magnetic inrush current and internal fault current in the differential protection of power transformer. The proposed method is based on the Wavelet Transform and correlation coefficient. In this study Discrete Wavelet Transform is used to describe the current signal in terms of different time and frequency components. In the proposed method, the energy signals of these components are employed. In the proposed method, a statistical parameter known as correlation coefficient is used to establish a criterion for the proposed discriminative algorithm. The correlation coefficient is used for express the relationship between wavelet coefficients energy at different scales of the signal resolution. Then pattern of these relations is utilized as a measure to discriminate the inrush current from fault current. For investigation the accuracy of the proposed algorithm different cases of inrush and internal fault currents is simulated by PSCAD/EMTDC software. Also, the proposed method is tested by the gathered data from experimental test at the laboratory. Current signals obtained from the simulation as well as the results obtained from the experimental test are employed by the proposed discriminative algorithm. Analysis of the simulation and experimental results show that the proposed method accurately identifies inrush and fault currents in the distance of the power transformer protection in a time period less than quarter of power frequency cycle. In addition to the sensitivity and high reliability, the proposed method has low computation work and does not required determining the threshold for each new power system.     

基于Sinc信号的变压器绕组频率响应曲线检测方法

为了克服传统脉冲频率响应法在检测电力变压器绕组变形缺陷时,高频分量衰减过快的缺点,文中提出了一种基于Sinc信号的变压器绕组频率响应曲线检测方法。然后文章从理论上对Sinc信号及脉冲信号的频率特性进行了比较,说明了Sinc信号的优越性。最后,分别利用Sinc信号及脉冲信号对实验室中定制的变压器绕组进行了检测试验,并采用相关系数指标比较了两种信号的检测效果。试验结果表明利用Sinc信号作为激励源可以得到稳定、宽频域的频率响应曲线,而且该方法的检测结果比传统脉冲频率响应法的检测结果更为准确。     

A multi-tone central divided difference frequency tracker with adaptive process noise covariance tuning

The problem of real-time frequency estimation of nonstationary multi-harmonic signals is important in many applications. In this paper, we propose a novel multi-frequency tracker based on a state-space representation of the signal with Cartesian filters and the second-order central divided difference filter (CDDF), which improves the performance of the extended Kalman filter (EKF) by using Stirling's interpolation method to approximate the mean and covariance of the state vector. A crucial element of the method is the adaptive scaling of the process noise covariance matrix appearing in the filter equations, as a function of the innovation sequence, which tunes the accuracy-reactivity trade-off of the filter. The proposed solution is evaluated against two approaches from the literature, namely the factorized adaptive notch filter (FANF) and the extended Kalman filter frequency tracker (EKFFT). Several experiments emphasize the estimation accuracy of the proposed method as well as the improved robustness with respect to initial errors and input signal complexity. The presented method appears to be particularly efficient with rapidly varying frequencies, thanks to the update mechanism that adjusts the filter parameters based on the amplitude of the estimation error.     

多频率尺度下的风电场短期风速预测融合算法

提出了一种基于多分辨率分析下的短期风速预测方法.利用小波分解将原始风速序列分解成低频信号分量和高频信号分量,将低频信号分量作为时间序列模型的输入,将高频信号分量作为最小二乘支持向量机的输入,输出未来时间段的各分量预测值.最后将各分量的预测值重构为风速序列的预测值.以内蒙古风电场为例进行仿真,结果表明文中方法显著提高了超前风速预测的精度.     

基于SOPC技术的多功能时钟同步装置

研究并设计了多功能的GPS时钟同步装置,该系统采用Altera公司的SOPC解决方案,配以GPS信号接收模块,可以准确地同外部输入GPS信号自动保持同步,频率和相位都能独立可调,能自动判断输入信号的频率,并向电子式互感器和电子式互感器校验仪提供同步时钟.经过多次现场试验表明,该装置达到了设计要求,取得了较好的应用效果.     

基于GA-BPNN的多频超声波变压器油密度检测研究

变压器油是电力变压器中的主要绝缘物质之一,油的密度指标与变压器的安全运行息息相关。文中基于多频超声波、遗传算法-反向传播神经网络(GA-BPNN)的原理,对变压器油密度进行了预测研究。以电网公司110组变压器油为例,其中100组为训练集,10组为预测集。建立了基于BPNN的变压器油密度预测模型,并将242维多频超声数据作为输入,密度作为输出。通过试验法确定了BPNN的隐层神经元个数,由此建立非线性映射关系,并用遗传算法优化BPNN的各层连接权值及阈值。结果表明,与传统的标准BPNN模型相比,GA-BPNN模型的变压器油密度值与实际值拟合度更高,误差更小。研究结果为检测变压器油的其他参数提供了可靠的依据。     

Application of linearized power system model to selection of PST controller input signal

This paper presents a selection method for phase shift transformer PST controller input signal. Simple conditions of input signal selection are obtained using frequency response analysis. The proposed method requires a suitable modeling of power system including PST device. The two types of power system models described in this paper are the nonlinear equations system model and the linearized model. The linearized model is represented as a block diagram transfer function model and as a state space representation model. The block diagram model presented in this paper has been used for the PST feedback input signal selection. Five locally available measurements at the switching node of the PST are considered. The results of frequency domain tests have confirmed that the block diagram transfer function model is a useful tool for power system analysis. The LQR method is used to achieve the final verification and the choice of input control signal.     

功率变压器的设计、制作和测试

功率变压器主要用来传输各种信号(单频、窄频、多频等)的功率,是现代电子设备的重要组成部分。本文主要介绍功率变压器的基本理论和设计方法,并结合当前发展状况,以单端反激式开关电源用变压器为例,详细论述了变压器的具体设计、制作过程,并且对样品进行测试和对比分析,为探究有效的测试分析方法和进一步的研究提供重要参考。     

基于暂态负荷的变压器保护一次电流检验方法

当测试负荷不足时,一次电流检验电流互感器（TA）二次回路的工作就无法完成,常造成新建变压器保护不能正常投入。为解决这一问题,提出一种采用电动机启动电流或变压器励磁涌流等暂态电流检验TA二次回路的方法。分析了变压器流过暂态负荷时两侧电流之间的关系,并根据不同接线组别对电流进行重构,以使两侧电流呈现比例关系。引入信号相关函数对电流波形进行分析计算,得到变压器两侧TA相对于基准间隔的相角差和变比,从而判定TA二次回路的正确性。该方法在工程现场检验结果与传统稳态负荷检验方法一致,证明了其可行性和正确性。     

Parameter Estimation for Power Transformer Models from Time-Domain Data

The existence of power system harmonics has been realized for many years. With the advent of new technologies and more solid state loads, power system harmonics are certain to increase both in amplitude and frequency bandwidth. Signal propagation in power systems depends on transformer impedances. Transformer impedances, on the other hand, are functions of signal frequency as well as input voltage and loading condition. Present power transformer models with single-valued parameters obtained from tests cannot adequately represent the transformer in the presence of harmonics. Accurate modeling of transformers must account for changes in signal frequencies and loading conditions as they occur. This paper presents algorithms for estimation of the parameters of a structurally known transformer model. These algorithms use time-domain data and continuously update the estimates, thereby accounting for changes in operating conditions. The techniques presented here can be applied to three-phase and single-phase N-winding transformers. The results of model identification for a single-phase two-winding transformer is given. The data acquisition system used and the problem of identification in a noisy environment are discussed. The simulated response of the identified model is compared with the transformer actual response.