Direct Power Control Strategy to Enhance the Dynamic Behavior of DFIG During Voltage Sag

One issue of using doubly fed induction generator operating in parallel with the grid is the vulnerability of the power-electronic converter when voltage sags in the supply terminals of the generator occur. The sudden reductions of voltage at the supply terminals of the generator produce high current transients in the stator and rotor windings. This transient can exceed the rotor-side converter limits and, consequently, the dc-link voltage limit. In order to improve the dynamic performance of stator and rotor current in this condition, a direct power control is proposed to improve the dynamic performance of the stator active and reactive power. The direct power control strategy is based on rotor voltage equation which does not ignore the transient stator voltage and flux. The consequence of the optimum stator power control is the reduction of the current peaks during the voltage sags. Experimental results show a good performance of the proposed strategy when the DFIG is subject the balanced and unbalanced voltage sags.