Comparative Group THD Analysis of Power Quality Disturbances using FFT and STFT

An important issue for many years for electric power utility companies and consumers is electric power quality (PQ). Power quality disturbances such as - transmission line faults, capacitor bank switching, transmission line energizing, wave distortion (voltage sag, voltage swell), and harmonics generated by power electronics converter results failure and malfunction of electrical & electronics equipment connected at the point of common coupling. Thus, an effective Index is required to measure power quality disturbances based on their severity. This paper deals with an analysis of PQ disturbances by comparing Group Total harmonic distortion (THDG) determined by the Short-Time Fourier Transform method and Fast Fourier Transform method. The research on the analysis of power quality disturbances is carried out by modeling and simulation in MA TLAB/Simulink. Besides, real transient signals of transformer transient and voltage sag are acquired using an experiment to validate the proposed index.