摘要
针对如何快速、准确地提取生物体触电故障暂态信号中的电力参数问题,提出了一种基于局部均值分解(local mean decomposition,LMD)的生物体触电时总泄漏电流信号瞬时参数提取方法,该方法首先利用局部均值分解将生物体触电时的总泄漏电流信号分解为一组乘积函数分量之和,每个乘积函数(product function,PF)分量可以表示为一个调幅信号和一个调频信号的乘积,然后由调幅信号和调频信号分别计算得到信号的瞬时幅值和瞬时频率。与采用希尔伯特黄变换方法相比,LMD具有瞬时频率曲线波动小和瞬时幅值函数端部失真小等优点。仿真信号分析结果表明:对测试信号进行LMD和经验模态分解(empirical mode decomposition,EMD)分解分别得到3个PF分量和5个IMF(intrinsic mode function)分量,分解前后信号的能量变化值分别为0.2851、0.5633,且LMD比EMD所需分解时间短0.0743s,与Hilbert变换相比,该文方法计算的瞬时幅值和瞬时频率更为平滑,在一定程度上避免了Hilbert变换计算过程中的负频率和端点效应现象。试验信号分析结果表明:对消噪后的总泄漏电流信号进行LMD和EMD分解,分别得到5和6个分量,分解前后信号的能量变化值各为0.5574、0.8896,所用分解时间分别为0.0835、0.2479 s;在求取瞬时频率方面,LMD方法求取的主导分量瞬时频率可判定生物体触电时刻,而经Hilbert变换求取的瞬时频率不仅无法判定生物体触电时刻,还出现了负的频率值,无法解释其物理意义;在求取瞬时幅值方面,该文方法与Hilbert变换求取的触电前总泄漏电流信号的瞬时幅值的平均值分别为11.3240、12.3728 m A,与原生物体无触电时总泄漏电流的幅值11.3538 m A的绝对误差分别为0.0298、1.0190 m A,另外,2种方法求取的生物体触电后总泄漏电流信号的瞬时幅值与原生物体触电后总泄漏电流的幅值的绝对误差分别为0.4340、0.6643 m A。因此,仿真信�
In order to quickly and accurately extract the electrical parameters in the transient signal of the electric shock caused by organisms, an instantaneous amplitude and frequency extraction method based on local mean decomposition（LMD） for the total leakage current signal of biological electric shock was proposed. The de-noising total leakage current signal was decomposed into a linear combination of a finite set of product functions（PF） and the amplitude modulated（AM） signal, and frequency modulated（FM） signal of each PF also could be obtained. The amplitude modulated signal was utilized to calculate the instantaneous amplitude and damping, while the frequency modulated signal was used to determine the instantaneous frequency. By using the method, compared with the Hilbert-Huang Transformation（HHT）, the curves of the instantaneous amplitude had less distortion in wave head and the instantaneous frequency had shorter swings. The method of HHT consisted of separation of the series data to components with different time scale（e.g. intrinsic mode function（IMF））, and empirical mode decomposition（EMD）, and application of the Hilbert Transformation to obtain the instantaneous amplitude and frequency of the signal from the IMF. The results of simulation signal showed that LMD and EMD were carried out on the test signal which was three PF components and five IMF components, respectively. The energy change values of LMD and EMD before and after decomposition was 0.2851, 0.5633, and the decomposition time of LMD was shorter than the EMD. Moreover, the instantaneous amplitude frequency based on the calculation of HT and integrated algorithm of PF appear the phenomenon of flying wings, but compared with the Hilbert transform, the proposed method to calculate the result was more smooth which can restrain endpoint effect to a certain extent and extract the instantaneous amplitude and frequency better. Experimental signal analysis results showed that LMD and EMD were carried out on the de-noising t
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2015年第17期221-227,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金项目(51177165)
国家电网公司科技项目(EPRI4108-150592)
关键词
故障检测
信号分析
泄漏电流
局部均值分解
瞬时参数
生物体触电
fault detection
signal analysis
leakage currents
local mean decomposition
instantaneous parameter
organisms electric-shocking
