Injecting reactive current during low-voltage fault ride-through (LVRT) is an essential requirement for wind turbines according to grid codes. The reliability of reactive current injection for doubly-fed induction generator (DFIG) wind turbines is subject to the stability of the phase-locked loop (PLL) and the DC voltage loop due to the interaction between the turbine and the grid

as well as DFIG's inherent characteristics

which poses the risk of control instability leading to failure of LVRT. From the perspective of the feasible region of the DFIG rotor current reference

this paper investigates the static instability mechanisms in reactive current injection under different fault conditions

considering the dual static stability constraints of the PLL and DC voltage under weak grid severe faults. The study provides a theoretical foundation for enhancing the reliability of reactive current injection in DFIG wind turbines. Case studies are carried out by simulations to verify the consistency of the analytical conclusions.