An Improved Angular Stator Flux Frequency Computation Method for Enhanced MPPT Operation of DFIG under Unbalanced Grid Voltage

Without tailored control measures, constant power generation and maximum power extraction under grid voltage dips in a smooth and uninterrupted manner are challenging control tasks owing to severe power and torque pulsations. The crux of this paper is to compute the angular stator flux frequency for precise reference power generation and control of DFIG subjected to grid voltage unbalance especially during MPPT operation. The angular frequency of stator flux is computed with the positive sequence stator voltage and current components in the stationary reference frame without the need for a PLL and differentiation of stator voltage vector. Further, the computed stator flux frequency signal is employed for rotor speed computation, and reference power generation for maximum power extraction from DFIG. The efficacy of the proposed method for DFIG operation under unbalanced grid voltage is demonstrated using simulations in PSCAD/EMTDC.