Mitigation of Voltage Sag using DPFC

Power systems, due to its dynamic nature regularly face disturbances and the increase in usage of non-linear loads creates high power quality issues. So to improve its performance there is need to mitigate the issues of power quality. Flexible AC Transmission Systems (FACTS) is an ideal solution for the reliability of AC grids, to improve energy quality, and transmission efficiency. The two major issues of power quality are Harmonics and voltage sags. Voltage sag is reduction in RMS voltage. Faults or starting of loads which are transformer, motors or supply power causes the voltage sags. The effects caused by voltage sags are Voltage stability, improper functioning of devices with less voltage and the control of communication signals. When the power system is subjected to these disturbances the FACTS device Unified Power Flow Controller (UPFC) which is a combined FACTS device contains a series, shunt voltage source converters which have the ability to protect the system by supplying the maximum requirement by the load.Compared to UPFC, the DPFC is also a combined device with both series and shunt VSC’s and the standard link between these converters is removed and a third-phase converter is separated from several single-phase converters that are distributed on the line to add reliability.In this project DPFC is proposed for mitigating the voltage sag and the corresponding block diagram, control scheme along with simulation results are presented.