Design and Control of Single Phase Dynamic Voltage Restorer

Dynamic Voltage Restorer (DVR) is a custom power device used in electrical distribution system for power quality improvement. The main application of DVR is for voltage compensation of sensitive loads against voltage disturbances such as voltage sag and voltage swell in distribution lines. It is a series connected device and is able to compensate voltage sag and voltage swell by injecting a voltage with the help of series transformer. The injection of an appropriate voltage component in the event of a voltage disturbance requires a certain amount of real and reactive power. Conventionally, DVR consists of an energy storage device which supplies the required power over the limited duration of the sags. Large magnitude and long duration of sags, lead to heavy financial investment in energy storage unit. To overcome this limitation, a single phase back-toback converter based DVR is implemented in this paper, which eliminates energy storage requirement. In the event of voltage sag, front-end converter acts as active rectifer and other converter acts as inverter, injecting the voltage in series with grid voltage. Real power flows from rectifer to inverter. In case of voltage swell condition, the operation of two converters interchanged and energy is fed back to the shunt converter from the series converter. The effectiveness of control schemes, protection schemes and plug and play operation of DVR is verified through detailed simulation studies. The viability of above schemes is confirmed by the experimental results generated from laboratory prototype developed. Keywords—Dynamic Voltage Restorer, In-phase compensation, Voltage Sag, Voltage Swell.