Dynamic Voltage Restorer For Voltage Sag Compensation

The Dynamic Voltage Restorer (DVR) is a power electronic device that is used to inject 3-phase voltage in series and in synchronism with the distribution feeder voltages in order to compensate for voltage sag. In this paper the operation of a DVR is presented. The power circuit of a DVR together with the control techniques used for compensation is explained. The operation of the Software Phase Locked Loop (SPLL) and its stability are analyzed. The DVR control system is described and verified using simulation. The control algorithm implemented using DSP was tested using generated input voltage signals and the results are also presented. The micro-cycle effect of battery current for balanced and unbalanced sag is also investigated.