可调阈值函数和能量阈值优化的电能质量扰动小波去噪方法

电能质量信号在采集、传输过程中受外界环境的影响会引入噪声干扰,有效去噪的同时保留突变点信息是治理电能质量的重要前提。给出了一种可调阈值函数,通过对可调参数的控制,可以使得该阈值函数在软硬阈值函数之间变动,兼具两者的优点。引入小波系数能量因子,以能量最大的尺度作为特征尺度,在此尺度上,子区间能量高于尺度能量者则为有效区间,进而提出采用有效区间局部阈值去噪的新阈值取法,同时考虑噪声和信号的小波系数随尺度不同的传播特性,引入算子对阈值进行修正。利用有效区间的局部阈值取法较传统的全局阈值取法更能反映信号小波系数的特征。仿真结果表明,利用新方法去噪效果更好,既较好地改善了去噪性能,同时也保留了信号的扰动突变点信息,去噪后扰动定位准确,模极大值点的位置很好地反映了扰动发生的起止时刻。

Wavelet denoising method for power quality disturbances based on adjustable threshold function and energy threshold optimization

In the process of power quality signal acquisition and transmission, noise interference will be introduced due to the influence of the external environment. It is an important prerequisite for power quality control to effectively denoise and retain the mutation information. An adjustable threshold function is given in this paper. By controlling the adjustable parameter, the new threshold function can be changed between soft and hard threshold functions. The wavelet coefficient energy factor is introduced, and the scale with the largest energy is taken as the characteristic scale. On this scale, the sub interval energy higher than the scale energy is the effective interval. Then a new threshold method using effective interval local threshold is proposed. In addition, considering the propagation characteristics of the wavelet coefficients of noise and signal with different scales, an operator is introduced to modify the threshold. Compared with the traditional global threshold method, the local threshold method based on the effective interval can better reflect the characteristics of wavelet coefficients. The simulation experiments prove that the proposed method not only improves the denoising performance, but also retains the disturbance mutation information. After denoising, the disturbance location is accurate, and the position of the modulus maxima can well reflect the occurrence and end time of the disturbance.