Direct power control for DFIG under unbalanced and harmonically distorted grid voltage in stationary frame

The paper presents the direct power control of doubly fed induction generator (DFIG) under unbalanced and harmonically distorted grid voltage in the stationary frame. Two alternative control targets, the balanced and sinusoidal stator current injected into the power grid, or the smooth DFIG electromagnetic torque to ensure reliable DFIG mechanic parts operation, can be achieved. The complicated and time-consuming grid voltage and stator current negative and harmonic components extraction, as well as power compensation item calculation according to the specific control targets, can be avoided in the proposed control strategy. Moreover, the proposed DPC strategy is implemented in stationary frame, thus no angle of grid voltage fundamental component by phase lock loop (PLL) is required. Therefore, the robustness against grid voltage unbalance and distortion disturbance and better dynamic response capability of the proposed strategy can be essentially ensured. The improved reduced order generalized integrator (ROGI) regulator is employed in stationary frame to regulate the ac signal of -50Hz (stator current negative component), -250Hz and +350Hz (stator current 5th and 7th harmonic component). On the other hand, the electromagnetic torque 100Hz and 300Hz pulsation is eliminated through the effective working of vector PI (VPI) regulators tuned at 100Hz and 300Hz. The availability of the proposed control strategy is validated by the simulation of MATLAB/Simulink.