Abstract: A vector control method based on the modified super-twisting observer and non-singular terminal

sliding mode was proposed for stand-alone doubly-fed wind power generation systems under unbalanced loads. The fundamental frequency and double frequency components of the rotor current were observed by the modified supertwisting observer，which reduces the dependence on the parameters of the doubly-fed wind power generation and improves the anti-interference ability of the system. A non-singular terminal sliding mode rotor current controller based on a modified super-twisting observer was designed，which eliminates the sliding mode surface fluctuation caused by unbalanced loads，enhances the tracking performance of theAC given，and improves the suppression ability of negative sequence stator voltage. Simulation and experimental results show that the proposed method can effectively suppress the negative sequence component of stator voltage under unbalanced load conditions，and has the excellent dynamic and static performance.

      Key words: doubly-fed induction generator（DFIG）；stand-alone；vector control；sliding mode control；supertwisting observer （STO）