Research on Improved S Transform for the Feature Extraction of Power Quality Disturbance Signal

As the widely use of electronic equipment and the limitation of distribution lines, power quality issues have been more and more critical, and quantifying the power quality, monitoring the power disturbances are getting more and more attention. It crucial for the electric compensation and the improvement of electrical safety to analyze the power quality issues and locate the disturbances. Because of the limitation that most time-frequency algorithms cannot take both time and frequency resolution into account, an improved S transform based on sigmoid function which is used to adjust window width factor is proposed to obtain the characteristics of electrical disturbances, such as occurrence time, magnitude, duration, harmonics and so on. By introducing evaluation index, to measure the effect of different methods on signal analysis. Through the simulation of different kinds of power quality disturbances, and comparing with the S transform, the improved S transform based on sigmoid has the advantages of high accuracy for the extraction of characteristics. Meanwhile, it meets the requirements of most power quality disturbances and the parameters setting are simple, hence the algorithm is convenient for applications. In practice, the effect of noise on power quality disturbance signal is effectively reduced by the improved S transform.