To address the limitation that the existing “three-component” frequency framework for short-circuit current calculation analysis cannot fully characterize the dynamic features of frequency coupling and shifting, an analysis approach explicitly capturing the stator–rotor coupling frequency shift effect is developed to improve the calculation accuracy of DFIG short-circuit currents under large-scale wind farm fault conditions. The method employs the internal rotor electromotive force as an unified intermediate variable to map the rotor-side transient behaviors (e.g., crowbar activation, rotor-side converter blocking/re-activation, excitation limiting) under different fault ride-through strategies into a unified state space, thereby resolving the dynamic discontinuity problem caused by non-zero initial states in the phased calculation process. On this basis, a unified transfer function relationship between stator voltage, stator current and rotor current during the ride-through process is established, and additional eigen poles introduced by control strategy switching are further derived to reveal the intrinsic mechanism of frequency shift of slip components and power frequency components under multi-stage control actions, which form multi-frequency coupled components. Meanwhile, following the same modeling idea as the rotor side, a unified transfer function relationship between the grid-side converter and stator voltage under different control strategies is established, revealing the additional harmonic components in the short-circuit current affected by the grid-side converter control from the frequency domain perspective. Case studies demonstrate that the proposed approach reduces the maximum error of the existing "three-component" framework, which is kept within 2.2% under shallow voltage sags and within 2.8% under severe voltage sags, exhibiting excellent robustness and adaptability. Meanwhile, the relevant harmonic component decomposition results effectively verify the existence of multi-frequency coupled components in the theoretical analysis, and based on this, effectively explain the relay maloperation mechanism caused by phasor amplification. The findings provide a theoretical basis for enhancing the accuracy of fault analysis in large-scale wind power systems, integrating stator–rotor frequency coupling effects and multi-stage control switching into a unified short-circuit current calculation framework, thereby achieving fast and accurate solutions under various complex fault conditions.