Transformers flux-linkage control in dynamic voltage restorer systems

This work proposes to control the flux linkage of the dynamic voltage restorer (DVR) transformers through a proper correction in the voltage injections. The flux-linkages are calculated by means of the voltages in the transformers that are injected by the DVR. In case of exceeding the maximum flux saturation, a form factor is determined and the voltage injected is modified within a half cycle and the flux is appropriately shifted, which avoid the maximum flux-linkage excursion from being exceeded. Even so, if the opposite peak of the flux keep exceeding, the correction is performed with elimination of dc flux and simultaneously, one set the amplitude to the maximum value allowed. From this, the transformer does not enter into saturation mode which contributes to efficiency of the DVR. Simulation and experimental results are shown to prove the effectiveness of the method.