Contents I. Introduction
Power quality in distribution systems has been attracting an increasing interest during recent years. Research studies include the quality of voltage supply with respect to temporary interruptions, voltage dips, harmonics, and voltage flicker. Voltage flicker occurs when large industrial loads, such as electric arc furnaces, rolling mills, and pumps operate periodically in a weak power distribution system. It causes voltage fluctuation at the Point of Common Coupling (PCC) with other loads and can annoy residential consumers by causing visible lighting flicker on incandescent or fluorescent lamps. The severity of the annoyance is generally dependent on the frequency and amplitude of the voltage variation and the short circuit rating at the PCC. It is reported that a small voltage fluctuation of less than 0.5% in the frequency range of 5–10 Hz can cause visible and uncomfortable incandescent flicker [1]–[2].