Dynamic Voltage Restorer (DVR)

Dynamic Voltage Restorer (DVR)

DVR injects a voltage component which is connected in series with the supply voltage, thus compensating the voltage sags and swells on the load side. Control response is of the order of 3msec, ensuring a secure voltage supply under transient conditions. The main function of a DVR is the protection of sensitive loads from voltage sags/swells coming from the network. The DVR is located on the basis of sensitive loads. 

Figure-1: Dynamic Voltage Restorer (DVR)

A DVR is connected in series with the feeder using a transformer. The low voltage winding is connected to the converter. If the objective of a DVR is mainly to regulate the voltage at the load bus, it remains for most of the time in stand-by mode during which the converter is bypassed (no voltage is injected). Only when sag is detected, the DVR injects a series voltage of the required magnitude Vdvr and compensates load voltage to pre fault value. The momentary amplitudes of the three injected phase voltages are controlled in such a way to eliminate any detrimental effects of a bus fault to the load voltage Vl.

 It is necessary to protect a DVR against the fault currents (as in the case of a SSSC) Figure shows the schematic representation of DVR. A DVR with IGBT/IGCT devices can be controlled to act as a series active filter to isolate the load from voltage harmonics on the source side. It is also possible to balance the voltage on the load side by injecting negative and/or zero sequence voltages in addition to harmonic voltages.

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Rajeev Kumar is dedicated to teaching and research in the field of electrical and electronics engineering. He is always sharing valuable content of the engineering field on this website.