Validation of SRFPI Control Methodology for Voltage Sag Compensation with a Dynamic Voltage Restorer to improve Power Quality

Abstract

Voltage sags are regarded as one of the most significant causes of disruption in power supply systems. The voltage sags cause adverse effects on sensitive equipment such as process-control equipment, computers, adjustable-speed drives, etc. During sag, the nominal voltage drops between 10% and 90% and lasts between 10ms and 100ms. Though the FACTS devices provide the solution to most of the PQ issues, it was observed that the drawback of these devices, however, is that they are very costlier. The disturbances in power lines are compensated by inserting voltages in series with the source using The Dynamic Voltage Restorer (DVR). The DVR can compensate with the proper magnitude and phase angle of the source voltage which necessitates the DVR to be operated with an independent external power source with high energy storage. This independent source may be a battery, a dc link and a capacitor bank. The limitations of such external storage usage have been addressed by many researchers, and here an attempt has been made to propose an improvised control methodology with the battery-supported DVR controlled by SRF PI control algorithm with a fast-operating DSP (Digital Signal Processor) to reduce the harmonics and to mitigate voltage sag.