The system described includes some other control elements in order to perform the voltage dip generation, which takes place as follows.
Having the by-pass switch (3) on allows the direct connection between the utility and the generating system (i.e. wind system), eliminating the effect of the insertion of the voltage dip generator.
Once this switch is open, the generator is connected to the grid through the series inductances (4), and the switch (6) connecting the parallel branch can be closed, in order to connect the primary of the transformer (7), which at this point is in no-load operation. Next, the dip generation switch (8) is closed, connecting the secondary of the transformer to the impedances (11) or to the short circuit (9) to achieve a deeper voltage dip. Timing the operation of these switches, the desired dip duration is set. As mentioned before, a 100% voltage dip can be achieved closing switches (5) and (9) after switch (3) has been open. The impedance banks (11) have single-phase switches (10) to have the possibility of performing single-phase, two-phase and three-phase tests.
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