基于改进阈值去噪的谐波检测

Harmonic detection based on improved threshold de-noising

为保证电力系统的安全运行,必须要对谐波进行准确的检测和分析。电力系统中的信号不仅由基波和各次谐波组成,还包含大量的噪声,噪声的存在严重影响电力系统谐波检测的精确性。针对传统的软阈值和硬阈值去噪方法的不足,提出了一种基于sym8小波的改进阈值去噪方法。首先用sym8小波对信号5层分解,然后对第一层、第二层小波系数去噪优化,最后基于优化后的各层系数对信号进行重构和谐波检测。在Matlab平台下对比软、硬阈值和改进阈值的去噪效果,表明改进阈值去噪方法效果更好,并用该方法去噪后检测谐波的准确性明显提高。

In order to guarantee the safe operation of power system,its harmonics must be accurately detected and analyzed. Signals in the power system not only consist of fundamental wave but also include harmonics and noises,which seriously affect the harmonic detection precision. In view of the shortcomings of traditional soft threshold and hard threshold de-noising methods,this paper provides an improved wavelet threshold de-noising method based on sym8.Firstly,the signals are decomposed to 5 layers with sym8 wavelet. Secondly,detail coefficients of the first and second layer are de-noised and optimized. Finally,based the optimized coefficients of each layer,the signals are reconstructed and harmonics are detected. On the Matlab platform,the de-noising effects of the soft threshold,the hard threshold and the improved threshold we proposed are compared. The result shows that the de-noising effect of improved threshold method is better,and the accuracy of harmonic detection is obviously improved.