A Control Scheme for Dynamic Voltage Restorer using PSCAD

The Dynamic Voltage Restorer (DVR) is a custom power electronic device to compensate the problems of voltage sags and voltage swells in the distribution lines. The main function is to inject the voltage difference (which can be determined as difference between the pre-sag and sag voltage) to the power line and helps to maintain the pre-sag voltage condition in the load side. Different type of control ideas are implemented depending on the techniques for compensation purpose. A new control scheme for the single phase voltage sags based on in-phase compensation technique. In this scheme, the Dynamic voltage restorer tracks the phase angle of the supply voltage and produces a reference voltage signal with the rated load voltage magnitude. If there is any phase jump generated at the supply voltage, then phase angle of the reference voltage signal is adjusted slowly leads to track the phase angle of the supply voltage. Then the injected voltage which is the difference between the reference and measured voltage is injected by the DVR. The simulation was simulated out using EMTDC/PSCAD (Electromagnetic transients including DC/Power system computer aided design Professional software version 4.1.0) and their results show various levels of compensation for voltage sags.