Comparative analysis of power quality using wavelets for real time implementation

With increasing demand for electric power globally, alternative energy sources such as wind and solar are integrated into the power supply grid. Integration technologies use power electronic converters and controllers which introduce harmonics and other power quality issues. In addition, growing usage of BLDC motors, UPS, LED lights, inverters, momentary usage of heavy machinery by domestic consumers has caused the harmonics and other power quality issues such as flicker, voltage sag and swell to penetrate into the power supply network. Real Time detection and mitigation of such events is therefore necessary. A framework for Real Time Power Quality Monitoring is discussed. Precise detection and localization of sag or swell events using Wavelet Packet Transform is carried out for a typical power system. Supply voltage signal fed to power electronic converter supplying a BLDC motor is compressed using Discrete Wavelet Transform (DWT) and Discrete Cosine Transform (DCT). For a compression ratio of 19.6923, DWT provide lesser Total Harmonic Distortion (THD) as compared to DCT. High frequency white noise present in the current signal supplying the BLDC motor converter is filtered using Wavelet Packet Transform.