Power quality disturbances denoising using modified S-transform

This paper presents a new approach of power quality disturbances denoising using modified S-transform which mitigates the defect of S-transform that white noise power spectrum lineally increases with frequency. So it´s more suited for analyzing noise signal than S-transform. The energy congregation level (ECL) is defined for determining the parameter g which can adjust the time-frequency resolution. And the ECL is also utilized to determine the order of the specific element that its module use as the threshold to rectify the elements of time-frequency matrix. The quadratic change rate of ECL is defined to find the optimal iterative number used in iterating algorithm to obtain satisfactory denoising results. Inverse transform of modified S-transform is taken to get the disturbance waveform after denoising. In the end of the paper the simulations are made to illustrate the validity of the proposed method and the results comparison with wavelet-based method are given.