Compensation of distribution system voltage sag by DVR and D-STATCOM

This paper describes the techniques of correcting the supply voltage sag in a distribution system by two power electronics based devices called DVR and D-STATCOM. A DVR injects a voltage in series with the system voltage and a D-STATCOM injects a current into the system to correct the voltage sag. The steady state performance of both DVR and D-STATCOM is determined and compared for various values of voltage sag, system fault level and load level. The minimum apparent power injection required to correct a given voltage sag by these devices is also determined and compared. The maximum voltage sag that can be corrected without injecting any active power into the system is also determined. Simulation results indicated that a DVR can correct a voltage sag with much less injected apparent power compared to that of a D-STATCOM.