Reactive Current Distribution Strategy of DFIG's RSC and GSC Considering Electromagnetic Stress and Grid Codes Requirement

The doubly fed induction generator (DFIG) based wind turbines are required to output positive- and negative-sequence reactive currents during asymmetric grid conditions by the latest grid codes. However, the electromagnetic stress, related to the reactive current settings of both the rotor- and grid-side converters (RSC and GSC) of the DFIG, will be aggravated. That is the oscillations in both the electromagnetic torque and DC-link voltage would be boosted up. To tackle such problem, the positive- and negative-sequence reactive currents need to be carefully distributed, so as to suppress electromagnetic oscillations while fulfilling the grid code requirements. To do so, in this paper, the influence mechanism of the positive- and negative-sequence reactive currents on the electromagnetic stress is firstly studied. Then, a coordinated reactive current distribution strategy, considering the electromagnetic stress, the grid code requirements, and the converters' capacity limit, is presented. Finally, electromagnetic simulations are conducted to validate the effectiveness of the proposed method.