Design and Implementation of Dynamic Voltage Restorer for Voltage Sag Mitigation

This paper introduces the terminology and various issues related to ‘power quality’. The power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency deviations that result in a failure of end use equipment’s. The main occurrence of voltage sag is always considered as one of the major power quality problems and it become severe to industrial customers. Voltage sag can cause mis-operation to several sensitive electronic equipment’s. This problem can be mitigated with voltage injection method using custom power device called ‘Dynamic Voltage Restorer’ (DVR). The performance of the DVR depends on the efficiency of the control technique involved in switching circuit of the inverter. This paper presents hardware implementation of the DVR with Sinusoidal Pulse Width Modulation (SPWM) based PI controller using AT89S51 Microcontroller. A DVR with its excellent dynamic capabilities, when installed between the supply and a critical load feeder, can compensate for voltage sags, restoring line voltage to its nominal value within a few milliseconds and hence avoiding any power disruption to that load. Keywords— Dynamic voltage restorer (DVR), AT89S51 microcontroller, sinusoidal pulse width modulation (SPWM), PI controller, voltage sag.