Coordinated control strategy of DFIG for balanced currents and constant torque during grid voltage unbalance

Effected by the unbalanced voltage conditions, various pulsations occur in the doubly-fed induction generator (DFIG) based wind turbines, each of which can be regarded as a control target. A coordinated control strategy of rotor-side converter (RSC) and grid-side converter (GSC) is proposed to eliminate the electromagnetic torque oscillation and attain balanced total currents which are the sum of stator and GSC input currents simultaneously. Both current references of RSC and GSC are calculated and the parameters of the adopted proportional integral plus resonant (PI+R) controller in the synchronously rotating reference frame to regulate positive and negative sequence currents are optimized. Simulation of the 1.5MW DFIG system is carried out in MATLAB and the results validate the proposed strategy.