I. Introduction
With the growth of the modern industrial equipments and non linear loads are prone to power quality issues such that voltage sag, swell, interruption, harmonics, flickers and transient. In industry voltage sag is the most frequent voltage disturbance typically caused by a fault at the bus, load and major cause due to starting of induction motor. It also affects the equipments and its performance in sensible load. Voltage sag also have disadvantageous in terms of economic impact as this phenomenon leads to the damage of equipments. Therefore maintain voltage profile and regulated voltage by mitigation of voltage sag is important phenomenon to overcome above problem. As per IEEE Std. 1159–1995, the voltage sag is defined as decrease in voltage between 0.1 to 0.9 p.u. in root mean square(rms) in a short period of time (10 ms until 1 min) [2], [8]. The amplitude of voltage sag is the remaining voltage during the sag. The characteristics of voltage sag as shown in Fig. 1 [4].
Definition of voltage sag according to IEEE std. 1159–1995
RMS representation of the voltage dip