To meet the grid code requirements on the wind turbine generators low voltage fault ride through capability， the characteristic of a fully converted wind turbine is studied under unbalanced system conditions. A model of the power converter under unbalanced grid conditions is established， and the problem existing in the control strategy of positive and negative sequence dual current is analyzed， a DC sample voltage with variable frequency notch function of dual current control strategy is proposed. When the system frequency fluctuates， a phase-locked loop for correcting the notch filter is added. Simulation results show that the proposed control strategy of dual current， DC feedback voltage with notch function has significant better dynamic regulation performance under asymmetry grid conditions.