The real power flow between the rotor and converter is bidirectional and it depends on the generator speed in comparison with Ns. If the generator is running above Ns, the power can be generated in both the stator and rotor. The power generated from the rotor is added with the power generated in the stator through back-to-back power converters. If the generator is running below Ns, the real power flows from the stator to the rotor. If the generator is running exactly at Ns, the power flows from the stator to the rotor to meet the winding resistance losses of the rotor.
The real component of the current is controlled by the phase difference of the rotor flux wave and the reactive component of the current is controlled by the magnitude of the rotor flux wave. By controlling the real and reactive currents from the control of power converters, the real power and terminal voltage of wind turbine generators can be controlled. Due to the fast control of back-to-back power electronic converters, type-3 wind turbine generators can provide constant real power and regulated terminal voltage response which is faster than the synchronous generator response.
References
Walling, R. A., Ekrem Gursoy, and Bruce English. "Current contributions from Type 3 and Type 4 wind turbine generators during faults." In PES T&D 2012, pp. 1-6. IEEE, 2012.
Muljadi, Eduard, et al. "Understanding dynamic model validation of a wind turbine generator and a wind power plant." 2016 IEEE Energy Conversion Congress and Exposition (ECCE). IEEE, 2016.