Review of Voltage Flicker Estimation Algorithms

The quality of electric power is of supreme importance to electrical utilities and their customers. Modern equipments are more sensitive to power system anomalies than in the past. Microprocessor based controls and power electronics devices are sensitive to many types of disturbances. Minor power disruptions, which once would have been noticed only as a momentary flickering of the lights, may now completely interrupt whole automated factories because of sensitive electronic controllers or make all the computer screens at an office go blank at once. In order to restart the whole production, computers, etc, a considerable time might be necessary, implying on significant financial losses to an industry. Hence voltage flicker caused by loads that exhibit continuous, rapid variations in load current is considered as a major power quality issue. In order to quantify the scale of flickering phenomenon, research has been conducted with the aims of developing measurement equipment, containment techniques and methods of mitigation. Accurate tracking and estimation of the voltage flicker levels are important for effective design and implementations of voltage flicker mitigation devices. Voltage flicker estimation incorporates measurement of flicker severity indicative parameters and estimation of voltage envelope, flicker frequency and phase angle of flickering voltage. This paper analyses measurement of flicker indicative parameters called short term flicker severity (PST) and long term flicker severity (PLT), estimation of envelope and phase angle of flickering voltage using ANN, application of the adaptive linear neuron (ADALINE) for determining total flicker distortion (TFD) which models the flicker voltage as a linear combination of orthogonal sinusoids with on-line frequency correction scheme for taking into account small-frequency variations of the base voltage waveform and estimation of the percentage relative voltage change of the voltage flicker which is modeled as an amplitude-modulated signal, and the voltage flicker, which is the modulating signal, is a sinusoid of random frequency and random magnitude.