Study of the out-of-phase connection of doubly fed induction generators

Distributed generation systems are acquiring day by day bigger relevance regarding the conventional ones due to the energy requirements and to the use of sources of ecological and renewable energy. Regarding the energies, one of the most developed is the wind energy, which in many cases uses generating machines of the asynchronous type with multiple excitation feeding. The study was carried out on an induction generator multiply excited, associated to a machine-transformer, to which the system or network was out-of-phase reconnected. This situation is presented when a portion of the system remain working as an island, after a fault has taken place, being quickly reconnected the region. From the test series carried out, it can be concluded that in case of a full out-of-phase connection of an induction generator, the obtained current values are approximately two times the ones obtained in case of terminals direct short-circuit. The behavior of the current varies according to if the out-of-phase connection takes place lightly before the opposition or after it. In the first case the balance position is reached without oscillating, on the other hand in the second situation a complete oscillation cycle takes place.