Control strategy of doubly-fed induction generator during the grid voltage swell

This study firstly derives the relationship between the grid voltage and the rotor current of doubly-fed induction generator (DFIG) during the grid voltage swell. Then, an effective control strategy aiming to restrain rotor over-current is proposed and the control strategy of the grid-side converter is also improved. The proposed rotor current suppression and grid voltage suppression method, cooperating with the DC chopper, can not only solve the problem of short circuit of the rotor side converter resulting from the frequent switching of crowbar device, but also maximally improve the capability of wind turbine in dynamic reactive power support without adding any other power electronic devices. With the help of this control strategy, the wind turbine could maintain its normal operation even during the fault and the high voltage ride through of wind turbine can be achieved. As a result, the stability of the wind power integration is significantly improved. Finally, the simulations and analysis in the power systems computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) verify the effectiveness and feasibility of the proposed control scheme.