Improved start-up procedure of a stand-alone wind system with doubly-fed induction generator

This paper proposes a start-up procedure with improved performance for stand-alone doubly-fed induction generator (DFIG) wind system. The forced start-up technique is considered and the suggested procedure provides smooth start-up of the wind system with minimum power consumption from the storage energy device. The start-up procedure can be activated at any wind speed conditions and the functional steps that are followed are governed by using only electric quantities and the rotational speed. The DFIG operates at synchronous speed in the stand-by condition for providing minimum iron rotor losses. The transition to generator operation is decided by indirectly sensing the wind speed increase through the DFIG speed and the rotor current. The system topology consists of a back-to-back converter at the rotor side and the stator is directly connected to the electric load. An energy storage system composed of a dc-dc converter and a battery bank is connected to the dc-link. Several simulation results are presented in order to validate the effectiveness and the operational improvements of the proposed start-up procedure.