An integral mathematical model of doubly-fed induction generator（DFIG）based wind turbine is developed under weak network conditions with voltage unbalance and distortion of fifth-order and seventh-order harmonics，where the influences of the negative sequence and harmonic components on the electromagnetic torque and stator active and reactive powers are modelled in details.An approach to suppress torque oscillations is then proposed，with a novel proportion integral-double frequency resonance（PI-DFR）current controller being designed and the rotor current references being re-arranged.It can effectively and quickly regulate both the positive/negative sequence and harmonic components，without the need of sequence decomposition of the rotor currents.Experiment results indicate that the proposed control can significantly suppress the torque oscillations and improve the power quality，and thus enhance the ride-through capability and operation reliability of DFIG-based wind turbine under adverse grid conditions.The work is supported by National Natural Science Foundation of China（No.50907057）and Scholarship Award for Excellent Doctoral Student Granted by Ministry of Education.