实时跟踪电压闪变幅度的移动不变小波分析方法

该文提出了一种移动不变的小波分析方法，用以分离电压闪变信号的闪变波形(包络线)。该方法利用线性相位复小波具有奇对称实部与偶对称虚部的性质，使得在小波变换域能方便地得到与被分析调幅信号对应的一对幅值相同、频率相同的正交信号，从而可方便地对本质为调幅信号的电压闪变实现解调制。与现有的同类方法相比，该文方法的显著特点是：采用二进塔式快速算法，而不是费时的移动不变算法或重构算法，即可达到移动不变效果；只须在3个尺度上进行小波变换，并且前2个尺度上只进行实系数平滑小波变换，第3尺度上只进行复系数细节小波变换；只需一个尺度上的细节小波变换系数。这些特点使得该方法具有快速、准确、便于实时跟踪闪变幅度的能力。

A SHIFT-INVARIANT WAVELET-BASED METHOD FOR TRACKING VOLTAGE FLICKER LEVEL

An shift-invariant wavelet-based method is presented to detect the envelope of voltage flickers. The method is based on the quadrature signal idea and a linear-phase complex wavelet with an odd real part and an even imaginary part. From the wavelet transform (WT) coefficients it is easy to construct a pair of quadrature components corresponding to the signal being analyzed with the same amplitude and the same frequency. Using the quadrature components we can demodulate an amplitude modulated signal and then pick up its envelope, or the flicker waveform in the case of voltage flicker. Compared with the existing methods the distinctive features of this method are: shift-invariant results from a fast dyadic pyramid algorithm not a time-consuming shift-invariant one or reconstruction one; two real smoothed WT at scales 1 and 2 and one complex detailed WT at scale 3 not both smoothed WT and detailed WT at many scales. These make the method fast, correct and able to track the flicker level instantaneously.