Automated control technique for a single phase dynamic voltage restorer

The Dynamic Voltage Restorer (DVR) is a commercially available, popular device to eliminate voltage sags and swells in the distribution lines. Its basic function is to inject the voltage difference (difference between the pre-sag and sag voltage) to the power line and maintains the pre-sag voltage condition in the load side. Different control strategies are available depending on the compensation technique used for compensation. A new control strategy for the single-phase voltage sags based on in-phase compensation technique is described in this paper. In the designed control, the DVR initially tracks the phase angle of the supply voltage and produce a reference voltage signal with the rated load voltage magnitude. If any phase jump occurred at the supply voltage, phase angle of the reference voltage signal is adjusted slowly to track the phase angle of the supply voltage. The difference between the reference and measured voltage is injected by the DVR. Therefore with this DVR control technique, the load will not experience any phase jump or dip. The simulation was carried out using EMTDC/PSCAD software and the results show a very good level of compensation for different voltage sags.