Minimum junction temperature swing for DFIG to ride through symmetrical voltage dips

Doubly-Fed Induction Generator (DFIG) system is popular for wind turbines above 1 MW. Existing issues for a DFIG system to ride through a symmetrical grid fault are addressed in terms of the internal and external challenges. Based on the conventional demagnetizing current control, the design procedure of an optimum demagnetizing coefficient is proposed considering the reactive current injection required by the modern grid codes, which guarantees same maximum rotor current between the fault occurrence and the duration of the reactive current injection. As the thermal behavior of the power semiconductor is mainly decided by its current, the minimum junction temperature swing can be achieved by using this control strategy. It is concluded that, regardless of the rotor speed, the demagnetizing coefficient is only related to the dip level. Compared with the traditional vector control, simulation results agree with the reduced junction temperature swing during fault period.