共查询到20条相似文献,搜索用时 9 毫秒
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本文通过对二维Hilbert-Huang变换方法的改进,提出了一种基于二维变分模态分解(VMD)和Hilbert变换的局部放电灰度图像特征提取方法。首先,利用局部放电样本生成相应放电灰度图;其次,以二维VMD算法分解各放电灰度图像,获取各个不同中心频率的模态分量;然后,通过四元数Hilbert变换得到各模态函数对应的特征图,并提取灰度纹理特征,构成各放电样本对应的特征向量;最后,以BP神经网络分类器对提取出的局部放电特征量进行分类和识别。实验结果验证表明,同二维Hilbert-Huang变换和传统放电灰度图特征提取方法相比,基于本文方法所得特征量具有更高的正确识别率,验证了该方法的可行性。另外,本文所采用的二维VMD-Hilbert方法为局部放电信号的频谱分析拓展了新的思路。 相似文献
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无论陆地配电网或是船舶电网中,单相接地所占故障的比例最大.当前采用高电阻接地方式的电网,在发生金属性接地或电缆单次放电时,接地电阻不但不能抑制过电压,反而使故障点电流增加.从单相接地实验出发,提出一种利用数学形态学中的Gradient变换和Closing变换级联的方式识别接地故障类型的方法.该方法能将金属性接地和间歇性接地区分开,并且忽略掉单次放电的情况.通过大量实验和仿真对该方法进行验证,该方法在不同条件下均有良好的故障识别能力. 相似文献
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针对非线性Wiener模型,提出基于小波分析的一种新的模糊辨识方法,具有这种模型的非线性系统可看作了一个线性子系统后接静态非线性增益所组成的模型。利用小波变换分析模型的稳态信息,可推导出形式简单的稀疏矩阵表达式,一致估计出Wiener模型中的静态非线性增益;然后即可利用系统的动态信息一致估计出模型的线性子系统参数,最后通过仿真说明了该系统的有效性和实用价值。 相似文献
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《Electric Power Systems Research》1997,41(3):185-190
This paper presents two simple fault detection schemes for radial and meshed transmission systems based on Fast Hilbert transformations of voltage and current signals at the substation terminal. The novel schemes ensure detection accuracy, selectivity and distinction between the two fault types as a bolted/fixed impedance or a high impedance non-linear fault. 相似文献
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利用Hilbert变换(HT)对配电系统中的电压闪变水平进行检测,并用等纹波滤波器来实现HT.与文献中所用方法相比,该文所用方法在数学上更简单,实现更容易.HT能够检测配电系统中的电压闪变和系统频率的变化,精度高,使电压闪变补偿装置更容易控制.采用了不同的电压闪变信号验证该方法.通过Matlab仿真,简述了影响检测精度的不同因素.仿真结果验证了HT的检测能力,表明HT在检测电压闪变方面具有良好的性能. 相似文献
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利用Hilbert变换(HT)对配电系统中的电压闪变水平进行检测,并用等纹波滤波器来实现HT。与文献中所用方法相比,该文所用方法在数学上更简单,实现更容易。HT能够检测配电系统中的电压闪变和系统频率的变化,精度高,使电压闪变补偿装置更容易控制。采用了不同的电压闪变信号验证该方法。通过Mat-lab仿真,简述了影响检测精度的不同因素。仿真结果验证了HT的检测能力,表明HT在检测电压闪变方面具有良好的性能. 相似文献
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为了分析电力系统暂态信号特性和计算暂态信号导数,依据采样信号拟合暂态信号函数表达式是一种可行方法,但现有的暂态信号拟合方法还存在拟合函数确定性和可导性方面的不足.针对这一问题,提出了一种基于希尔伯特变换的电力系统暂态信号正弦表示分析方法,采用暂态信号的正弦表示构成拟合基函数,利用希尔伯特变换以满足拟合函数的确定性.与现... 相似文献
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《International Journal of Electrical Power & Energy Systems》2012,43(1):208-219
The paper introduces a practical approach to power system fault location in power networks using advanced fault signal processing. The three-phase fault voltages are converted to the vector of absolute values of its complex space-phasor. This vector represents fault traveling wave and it is further processed for fault location finding with the Hilbert–Huang transform. The simulation results, including single line to ground faults, faults in mixed feeders and high-impedance arcing faults, confirm the accuracy and practical applicability of the proposed approach. 相似文献
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《International Journal of Electrical Power & Energy Systems》2013,45(1):597-603
This paper employs Empirical Mode Decomposition (EMD) combined with Hilbert Transform (HT) to detect the voltage sag causes. Any power quality disturbance waveform can be seen as superimposition of various oscillating modes. It becomes necessary to separate different components of single frequency or narrow band of frequencies from a non-stationary signal to identify the causes which contribute to power quality disturbances. The main characteristic feature of EMD is that it decomposes a non-stationary signal into mono component and symmetric signals called Intrinsic Mode Functions (IMFs). Further, the Hilbert transform is applied to each IMF to extract the features. Then, Probabilistic Neural Network (PNN) classifier is constructed based on EMD which classifies these extracted features to identify the type of voltage sag cause. Three voltage sag causes are taken for classification (i) fault induced voltage sag, (ii) starting of induction motor and (iii) three phase transformer energization. A comparison of EMD with Wavelet Transform (WT) is made. The performance of PNN is compared with Multilayer Neural Network (MLNN) based on the above mentioned two methods. Simulation results show that the EMD method in combination with PNN is more efficient in classifying the voltage sag causes. 相似文献
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A new method is presented to reduce the high torsional torques induced in turbine-generator shafts during the clearing of multiphase faults. This method is based on controlling the sequential interruption of such faults. In this context, investigations have been conducted on two turbine-generator units of different designs for both three-phase and double line-to-ground faults. The effectiveness of the proposed method is illustrated through parametric studies and simulation results. The effects of the fault clearing time, the strength of the system to which the unit is connected, and the fault incidence instant on the effectiveness of the method have also been investigated 相似文献
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The authors present a method of reducing the high torsional torques induced in turbine-generator shafts during high-speed reclosure of multiphase system faults. The method is based on the sequential reclosing of the faulted circuit. In this context, investigations have been conducted on two turbine-generator units of different designs for various multiphase system faults. The results of both the three-phase-to-ground and double-line-to-ground faults are reported, and the effectiveness of the method is illustrated through parametric studies and simulation results. The effects of the reclosing time and the fault incidence instant on the effectiveness of the method have also been investigated 相似文献
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Kawada M. Tungkanawanich A. Kawasaki Z.-I. Matsu-Ura K. 《Power Delivery, IEEE Transactions on》2000,15(2):467-471
Recently, diagnostic techniques have been investigated to detect a partial discharge (PD) associated with a dielectric material defect in a high-voltage electrical apparatus. Gas insulated switchgear (GIS) is an important equipment in a substation, it is highly desirable to measure a partial discharge (PD) occurring in GIS which is a symptom of an insulation breakdown. As it is important to develop a noncontact method for detecting the insulation fault, this paper proposes a new method to detect the wide-band electromagnetic (E-M) wave emitted from PD using the Wavelet transform. The Wavelet transform provides a direct quantitative measure of spectral content, “dynamic spectrum”, in the time-frequency domain. This paper experimentally shows the “dynamic spectrum” of the wide-band E-M wave emitted from PD in the time-frequency domain. This method is shown to be useful for detecting the symptom of the insulation breakdown occurring in GIS 相似文献
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《Electric Power Systems Research》1997,42(2):95-107
This paper eamines the damping effect of flywheel dampers installed at different shaft couplings on torsional oscillations on the 951 MW turbine-generator shafts due to network faults. A studied system is described and torsional fatigue on the turbine shafts following various electrical system disturbances is analyzed and evaluated. Moreover, the influence of the safety factor selected and set at the design stage to the shaft life expenditure due to fatigue damage is also presented. Useful additional insight into their modes of operation is obtained from the fast Fourier transform of the transient response results. All computer simulations thus show that the proposed dampers are effective in suppressing the torsional oscillations on the shafts. In this paper, time-domain torque evaluation is also combined with the fast Fourier transform method to derive a selection procedure for obtaining suitable flywheel dampers to depress the amplitude of these critical shaft oscillations to acceptable levels. 相似文献
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为克服目前小电流接地系统单相故障发生在相电压过零点附近选线方法灵敏度低的缺点,提出了一种基于希尔伯特变换的综合选线判据。将零序电流进行小波包分解的同时,运用希尔伯特变换对分解结果进行瞬时频率分析,计算频带能比因子。将频带能比因子作为启动选线方法的条件,当高频分量多时比较小波高频能量,当低频分量多时比较直流分量能量,将两种方法进行有机综合可以构成完善的故障选线方案。仿真结果表明该方法有效、准确、且适用性强,不受系统结构和运行方式等的影响。 相似文献
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推导了水轮发电机组的电磁力矩和电磁刚度的表达式,建立了考虑转子支臂刚度并在水力转矩和电磁力矩耦合作用下的轴系统机电耦联扭振模型。研究了轴系统扭振特性随转子转动惯量、支臂刚度、转轮水体附加质量的变化规律。分析了不同频率的水力激励对转子扭振响应的影响规律,得出了轴系最大扭矩内力、扭振角和电磁力矩的频响曲线。研究水力激励频率等于零频和一阶频率时的机电耦联共振特性,给出了激磁电流和内功率角对扭振的影响,揭示了机电耦联振动规律,为水电机组的设计与安全稳定运行提供理论依据。 相似文献