Improvement of power quality monitoring based on modified S-transform

Detection of power quality disturbance is most essential to ensure the good Power Quality (PQ). The power disturbance signal will reduce the reliability of power system and create some disadvantage on operation process. Aging of electrical device, incorrect measurement, devices malfunction are the consequence of this condition. The characteristic of power disturbance signals are non-stationary and the way to detect this disturbance needed a sample method. The term of non-stationary in signal processing is regularly used to define a process in which the spectrum is changing with time. One kind of methods for analyzed this problem is S-transform (ST). However, Due to this method have relatively fixed Gaussian window the S-transform cannot provide satisfactory time-frequency resolution for all types of disturbance signals. Modified S-transform (MST) provides more suitable means for achieving desired time-frequency for several PQ disturbances signals. This paper proposes power quality analysis (PQA) using modified S-transform (MST) method. Both the time and the frequency domain information of each PQ component are extracted by MST. Comparison between MST simulation result and ST is applied to validate the accuracy and efficiency of modified S-transform (MST) method algorithm. The result of simulation show that this method can accurately detect and show the power signal disturbance such as voltage sag, voltage swell, interruption, flicker, oscillatory transient, notch, spike, and harmonic.