Single Phase Dynamic Voltage Restorer

It compensates for voltage sag or swell.

It measures the source side voltage and this voltage is subtracted from desired voltage. This voltage is reference voltage that needs to be injected in series. Inverter is employed to inject the voltage. Output votage of inverter is compared to reference voltage and gate signal is generated. Output of inverter is connected in series to line with isolation transformer. In this way, votage sag and swell is compensated.