Stator Current Calculation and Validation for DFIGs With Multiple Control Strategies Under Weak Grid Faults

This paper investigates the fault current characteristics of doubly-fed induction generators (DFIGs) in weak grid scenarios, addressing the limitations of existing methods that assume a predefined voltage dip and neglect the influence of DFIGs on post-fault voltage. A transient fault voltage model is proposed to accurately capture the interaction between DFIGs and weak grid impedance, which significantly affects fault current calculation. The model introduces an additional pole to account for fault voltage transients, addressing computational errors in low grid strength conditions. Furthermore, a fault current expression for DFIGs under severe faults, particularly after crowbar activation, is derived, revealing the impact of external grid impedance on transient fault currents. Case studies with expanded fault scenarios and hardware-in-loop experiments demonstrate the superiority of the proposed method over existing approaches in weak grid applications.