Design Requirements for a Dynamic Voltage Restorer for Voltage Sags Mitigation in Low Voltage Distribution System

Abstract

Power quality issues have become an increasing concern due to an increase of sensitive loads in distribution system. A power disturbance can be classified as voltage sag, swell, over voltage, under voltage, surge, outage, etc. From power quality surveys, it can be concluded that voltage sags are the most common power disturbances and main cause of power disruption. Therefore, this paper focuses on voltage sags and their mitigation. Dynamic Voltage Restorer (DVR) is one of the effective power custom devices is used in mitigation of voltage sags in distribution system. A DVR is basically a controlled voltage source installed between the supply and a critical and sensitive load. It injects a voltage on the system in order to compensate any disturbance affecting the load voltage.
This paper also discusses the active power injection requirements for a DVR under various system and load conditions, for different fault types, for three-phase load and for single-phase load. It is shown that the power requirement depends on the sag magnitude and phase-angle jump as well as on the power factor of the load. Voltages and power injected from each of the three phase DVR phases can be calculated by the formulated equations. Finally the DVR prototype is described and used to verify the effectiveness of a DVR