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双树复小波域的MRI图像去噪

中国图象图形学报 2016年第1期21卷 104-113页

作者：黄学优张长江浙江师范大学数理与信息工程学院金华321004

目的噪声会降低磁共振图像(MRI)的质量,影响视觉效果和计算机辅助诊断,针对MRI噪声的莱斯(Rician)分布特性,设计一种有效的MRI去噪算法。方法在双树复小波(DT-CWT)域结合双边滤波器(BF)和基于Stein无偏误差估计的邻域收缩法(Neigh Shrin... 详细信息

目的噪声会降低磁共振图像(MRI)的质量,影响视觉效果和计算机辅助诊断,针对MRI噪声的莱斯(Rician)分布特性,设计一种有效的MRI去噪算法。方法在双树复小波(DT-CWT)域结合双边滤波器(BF)和基于Stein无偏误差估计的邻域收缩法(Neigh Shrink SURE)、二变量收缩法(Bivariate Shrink)设计一种有效的磁共振图像MRI去噪算法。所设计的算法充分考虑了MRI的噪声分布特性以及小波系数的层间和层内相关性,其性能优劣主要取决于平方MRI的双树复小波系数的噪声标准差估计的准确程度,其次和双边滤波器的参数以及两种收缩方法的占比有关。为了使各算法的协同发挥最好的性能,以均方误差(MSE)、峰值信噪比(PSNR)和结构相似度(SSIM)作为图像质量评价指标,修正DT-CWT系数的噪声标准差,确定最佳双边滤波参数以及两种收缩方法的占比。在双树复小波域结合3种方法设计了一种有效的MRI去噪算法。结果与现有几种算法进行图像去噪比较实验。在视觉效果、去噪指标PSNR和SSIM以及耗时方面,本文算法综合性能优于现有的几种MRI去噪算法,PSNR提高了约0.5 1 d B,SSIM提高了约5%10%。结论双树复小波域的去噪优于基本小波去噪,利用层内和层间相关性的去噪算法很好去除了噪声,双边滤波器的使用增强了低频部分的图像,使得本文算法在MRI莱斯噪声的去除上获得了较好的表现,在去噪的同时能够保留边缘和细节信息。

关键词： MRI去噪双树复小波邻域收缩二变量收缩双边滤波

变频谐振下10 kV电缆缺陷局部放电检测研究

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电网与清洁能源 2023年第9期39卷 101-105,115页

作者：黄雪莜梁倩仪熊俊广东电网广州供电局广东广州510000

采用目前方法检测电缆缺陷局部放电时,因变频谐振PD信号的影响而导致其整体有效性较差。提出变频谐振下10 kV电缆缺陷局部放电检测方法。在二阶包络线的基础上提取局部放电信号脉冲,并通过阈值策略消除局部放电信号中存在的噪声,避免其... 详细信息

采用目前方法检测电缆缺陷局部放电时,因变频谐振PD信号的影响而导致其整体有效性较差。提出变频谐振下10 kV电缆缺陷局部放电检测方法。在二阶包络线的基础上提取局部放电信号脉冲,并通过阈值策略消除局部放电信号中存在的噪声,避免其对检测过程造成干扰;提高局部放电脉冲信号的时域波形、频域波形特征量,将其输入BP网络中,在变频谐振下完成10 kV电缆缺陷局部放电检测。实验结果表明,所提方法的识别率高,其检测结果的相对误差低。

关键词：变频谐振电缆缺陷局部放电检测二阶包络线 BP网络

Transient Simulation Model for Electric Field Distribution in Cable Joint

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Transient Simulation Model for Electric Field Distribution i...

作者： Lei Liao Ruxin Zhang Gang Du Mingyan Wu Zheng Wu xueyou huang Haiming Li Jian Zhang Binxian Lu Guagnzhou Power Supply CSG North China Electric Power University

The analysis of the impact of the switching impulse voltage on the internal electric field of the cable joint plays a key role in studying the breakdown of the *** this paper,the finite element method is used to simulate the transient electric field of the axisymmetric model of the cable *** changing the closing moment,the influence of different closing moments on the electric field intensity distribution is studied and *** results show that under the switching voltage excitation,when the closing moment at t0=nT,the electric field distribution in the cable joint is consistent with the steady state without ***,the point near the root of the stress cone will distort when the switch is closed,the closing moment is at 7.5 ms,which is the most *** closing time is at 10 ms,has the greatest influence on the electric field intensity distribution in the cable joint,especially the stress cone end,the bottom of the high voltage shield and the position near the high voltage conductor in the air domain.

关键词： Cable joint switching impulse voltage electric field intensity distribution finite element method

Research on Simulation Methods of Electric Field Intensity on Surface of 10 kV Cable Joint

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Energy and Power Engineering 2020年第4期12卷 37-45页

作者： Ruxin Zhang Jun Xiong Zheng Wu Lei Liao Mingyan Wu Gang Du xueyou huang Wenpei Jin Haiming Li Jian Zhang Wenli Cheng Binxian Lu Guagnzhou Power Supply CSG Guangzhou China Department of Electrical and Electronic Engineering North China Electric Power University Beijing China

The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field-circuit coupling method and equivalent circuit method. The average EFI of the inner surface of the outer semi-conducting shield can be calculated from the current in the measuring circuit. The relative error between these two methods is about 15%, which roughly proves the consistency of the two methods. Further practical application research enables online monitoring of cable joints.

关键词： Cable Joints Electric Field Intensity Equivalent Circuit Method Field-Circuit Coupling Method Finite Element Simulation Software

Nonlinear Switching Transient Field Simulation of Cable Joint without Residual Charge

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Energy and Power Engineering 2020年第4期12卷 46-52页

作者： Mingyan Wu Jun Xiong Lei Liao Lu Zhu Ruxin Zhang Zheng Wu Gang Du xueyou huang Haiming Li Jian Zhang Sizhuo Liao Binxian Lu Guagnzhou Power Supply CSG Guangzhou China Department of Electrical and Electronic Engineering North China Electric Power University Beijing China

The analysis of the impulse voltage on the internal electric field of the cable joint plays a key role in studying the breakdown of the joint. Based on the finite element method, a three-dimensional electromagnetic field simulation model of the cable joint is established in this paper. Simulation results show that the voltage at the head of the cable joint reaches about twice the impulse voltage. The increase of the conductivity of semi-conductive material also leads to the increase of electric field intensity. Then, several points and curves at different positions are selected for further analysis in this paper. Among them, the electric field distortion at the edge of the high voltage shield is the most serious and the electric field in the air gap is the least.

关键词： Cable Joint Switching Transient Field 3D Transient Electromagnetic Simulation Model Finite Element Method

Simulation of Electric Field Distribution in Cable Joint under the Influence of Metal Particle

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Simulation of Electric Field Distribution in Cable Joint und...

作者： Zheng Wu Mingyan Wu Ruxin Zhang Lei Liao Gang Du xueyou huang Wenpei Jin Ji'an Zhang Haiming Li Binxian Lu Guagnzhou Power Supply CSG

The middle joint of 10 kV cable is a kind of cable accessory that needs to be installed *** conditions may cause defects in the joints during *** to the small size of some defects,it is impossible to obtain accurate results when simulating them with all simulation domain *** this paper,an accurate model is established to accurately calculate the distribution of electric field around particles in the whole model,and the error in the central region of the model is less than 6.5%.When there are metal particles on the main insulation surface of the cable,this accurate model is applied for analysis,and the maximum electric field intensity around the metal particles is calculated to be 7 kV/mm,which is 3.8 times larger than normal.

关键词： Numerical interpolation Finite element method Cable joint Metal particle Accurate model

Nonlinear Switching Transient Field Simulation of Cable Joint without Residual Charge

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Nonlinear Switching Transient Field Simulation of Cable Join...

作者： Mingyan Wu Jun Xiong Lei Liao Lu Zhu Ruxin Zhang Zheng Wu Gang Du xueyou huang Haiming Li Jian Zhang Sizhuo Liao Binxian Lu Guagnzhou Power Supply CSG Department of Electrical and Electronic Engineering North China Electric Power University

关键词： Cable Joint Switching Transient Field 3D Transient Electromagnetic Simulation Model Finite Element Method

Research on Simulation Methods of Electric Field Intensity on Surface of 10 kV Cable Joint

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Research on Simulation Methods of Electric Field Intensity o...

作者： Ruxin Zhang Jun Xiong Zheng Wu Lei Liao Mingyan Wu Gang Du xueyou huang Wenpei Jin Haiming Li Jian Zhang Wenli Cheng Binxian Lu Guagnzhou Power Supply CSG Department of Electrical and Electronic Engineering North China Electric Power University

The electric field intensity（EFI） is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field-circuit coupling method and equivalent circuit method. The average EFI of the inner surface of the outer semi-conducting shield can be calculated from the current in the measuring circuit. The relative error between these two methods is about 15%, which roughly proves the consistency of the two methods. Further practical application research enables online monitoring of cable joints.

关键词： Cable Joints Electric Field Intensity Equivalent Circuit Method Field-Circuit Coupling Method Finite Element Simulation Software

基于残差卷积神经网络的开关柜局部放电模式识别

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中国电力 2021年第2期54卷 44-51页

作者：黄雪莜熊俊张宇刘辉陈鹭孟祥麟江秀臣广州供电局有限公司荔湾供电局广东广州510150 上海交通大学电气工程系上海200240

传统的开关柜局部放电模式识别方法缺乏一定的泛化性能且识别准确率低,难以在实际工程中应用。提出了一种基于残差卷积神经网络的开关柜局部放电模式识别方法,通过在网络中加入残差模块以解决随着网络层数加深导致准确度饱和后出现退化... 详细信息

传统的开关柜局部放电模式识别方法缺乏一定的泛化性能且识别准确率低,难以在实际工程中应用。提出了一种基于残差卷积神经网络的开关柜局部放电模式识别方法,通过在网络中加入残差模块以解决随着网络层数加深导致准确度饱和后出现退化的问题,并综合利用开关柜局部放电数据的浅层与深层特征融合学习,实现模式识别。通过开关柜不同绝缘缺陷类别的局部放电模拟实验与配电站现场检测,构建了开关柜局部放电数据样本库,并进行了实验分析。实验结果表明:所提方法的识别正确率达96.06%,相比传统识别方法至少提高了20.22%,且随着训练集样本数量的增加,识别率有更大提升。综合使用特征层融合模块和残差模块,显著提升了模型的泛化性能,更适用于实际工程。

关键词：卷积神经网络残差模块特征层融合局部放电模式识别