Voltage Sag Compensation of Induction Motor with 6 Pulse VSI based DVR

Now a day, Voltage sag problem in power system is important phenomenon. Basically voltage sag problem occurred where induction motors are used. Generally, in industries this phenomenon occurred most of the time due to motor loads. The aim therefore is to mitigate the voltage sag & to maintain proper voltage waveform by Dynamic Voltage Restorer (DVR). DVR has recently introduced and incorporated to protect industrial equipments from voltage sag and other voltage disturbances occurred. Modeling of DVR using 6 pulse VSI based converter, voltage sag mitigation due to motor loads in refinery and industries and their simulations are given in this paper. A DVR is shown to mitigate voltage sag provided with closed loop voltage system. Extensive simulation has been carried in PSCAD/EMTDC software.

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]. Fig. 1.

Definition of voltage sag according to IEEE std. 1159–1995

Fig. 2.

RMS representation of the voltage dip