Voltage regulation using dynamic voltage restorer for large frequency variations

The paper discusses the voltage regulation of a critical load bus using a dynamic voltage restorer (DVR) in a distribution system. The critical load cannot tolerate any power quality (PQ) disturbance including large frequency variations occurring in the system. The DVR is operated such that it holds the voltage across the critical load bus terminals constant at system nominal frequency irrespective of the changes occurring in frequency in the source voltages. To compensate for frequency variation the dc link of the DVR is supplied through an uncontrolled rectifier that provides a path for the real power required by the critical load to flow. The reference values of the injected voltages by the DVR are generated and are tracked with their actual values in the closed-loop output feedback switching control. Through simulation studies using PSCAD/EMTDC and frequency spectrum it is shown that the voltage is completely regulated across the critical load.