Tracking the impedance of fluctuant load using wavelet transform

Flicker has been an important concern of power quality in power system which is regarded as the human perception to the light flux of lamps and lanterns. As the flicker is produced from the voltage RMS value change, the analysis of flicker is usually on the base of RMS value tracking of voltage. It can help to flicker measurement but can not distinguish the flicker source. In fact, fluctuant bulky load is generally thought to be the source of voltage flicker. Although the voltage and current of load fluctuate together in the presence of flicker present, the impedance parameter of invariable load won´t vary with the supply voltage. So, above quantization of load fluctuation will help to search for the fluctuant load and ascertain the contaminated source. Conventional Fourier-transform based detection method was used to compute pst and pit. It only pays attention to the frequency-domain information and entirely neglects the non-steady character of general flicker. Newer wavelet-based algorithm is suitable for analyzing the non-steady fluctuation of signal. It is acceptable to be used to quantitate the load fluctuation.