In the conventional structure of the wind turbines along with the doubly-fed induction generator (DFIG), the stator is directly connected to the power grid. Therefore, voltage changes in the grid result in severe transient conditions in the stator and rotor. In cases where the changes are severe, the generator will be disconnected from the grid and consequently the grid stability will be attenuated. In this paper, a completely review of conventional methodes for DFIG control under fault conditions is done and then a series grid side converter (SGSC) with sliding mode control method is proposed to enhance the fault ride through capability and direct power control of machine. By applying this controlling strategy, the over current in the rotor and stator windings will totally be attenuated without using additional equipments like as crowbar resistance; Moreover, the DC link voltage oscillations will be attenuated to a great extent and the generator will continue operating without being disconnected from the grid. In addition, the proposed method is able to improve the direct power control of DFIG in harmonically grid voltage condition. To validate the performance of this method, the simulation results are presented under the symmetrical and asymmetrical faults and harmonically grid voltage conditions and compared with the other conventional methods.
 A. Geniusz, S. Engelhardt and J. Kretschmann, “Optimised fault ride through performance for wind energy systems with doubly fed induction generator,” in Proceedings of the European Wind Energy Conference & Exhibition, Brussels, pp. 1-9, 2008.
 M. Rahimi and M. Parniani, “Grid-fault ride-through analysis and control of wind turbines with doubly fed induction generators,” Electric Power Systems Research, vol. 80, no. 2, pp. 184-195, 2010.
 A. H. Kasem, E. F. E1-Saadany, H. H. E1-Tamaly and M. A. A. Wahab, “An improved fault ride-through strategy for doubly fed induction generator-based windturbines,” IET Proceedings on Renewable Power Generation, vol. 2, no. 4, pp. 201-214, 2008.
 J. Vidal, G. Abad, J. Arza and S. Aurtenechea, “Single-phase DC crowbar topologies for low voltage ride through fulfillmentof high-power doubly fed induction generator-based wind turbines,” IEEE Transactions on Energy Conversion, vol. 28, no. 3, pp. 768-781, 2013.
 L. Peng and Y. Li, “Improved crowbar control strategy of DFIG based wind turbines for grid fault ride-through,” IEEE Transactions on Industrial Electronics, vol. 40, no. 1, pp. 1932-1938, 2009.
 M. Rahimi and M. Parniani, “Efficient control scheme of wind turbines with doubly fed induction generators for low voltage ride-through capability enhancement,” IET Proceedings on Renewable Power Generation, vol. 4, no. 3, pp. 242-252, 2010.
 C. Wessels, F. Gebhardt and F. Wilhelm Fuchs, “Fault ride-through of a DFIG wind turbine using a dynamic voltage restorer during symmetrical and asymmetrical grid faults,” IEEE Transactions on Power Electronics, vol. 26, no. 3, pp. 807-815, 2011.
 O. Abdel, B. Nasiri and A. Nasiri, “Series voltage compensation for DFIG wind turbine low-voltage ride-through solution,” IEEE Transactions on Energy Conversion, vol. 26, no. 1, pp. 272-281, 2011.
 E. El-Hawatt, M.S. Hamad, K.H. Ahmed and I.F. El Arabawy, “Low voltage ride-through capability enhancement of a DFIG wind turbine using a dynamic voltage restorer with adaptive fuzzy PI controller,” in Proceedings of the International Conference on Renewable Energy Research and Applications, Spain, pp. 1234-1239, 2013.
 B. B. Ambati, P. Kanjiya and V. Khadkikar, “A low component count series voltage compensation scheme for DFIG WTs to enhance fault ride-through capability,” IEEE Transactions on Energy Conversion, vol. 30, no. 1, pp. 1-10, 2015.
 L. Yang, Z. Xu, J. Østergaard, Z.Y. Dongand K. P. Wong, “Advanced control strategy of DFIG wind turbines for power system fault ride through,” IEEE Transactions on Power Systems, vol. 27, no. 2, pp. 713-722, 2012.
 M. Darabian, A. Jalilvand and R. Noroozian, “Combined use of sensitivity analysis and hybrid wavelet-psoanfis to improve dynamic performance of DFIG-based wind generation,” Journal of Operation and Automation in Power Engineering, vol. 2, no. 1, pp. 49-59, 2014.
 H. Khorramdel, B. Khorramdel, M. Tayebi Khorrami and H. Rastegar, “A multi-objective economic load dispatch considering accessibility of wind power with here-and-now approach,” Journal of Operation and Automation in Power Engineering, vol. 2, no. 1, pp. 60-73, 2014.
 M. I. Martinez, G. Tapia, A. Susperregui and H. Camblong, “Sliding-mode control for DFIG rotor and grid-side converters under unbalanced and harmonically distorted grid voltage,” IEEE Transactions on Energy Conversion, vol. 27, no. 2, pp. 328-339, 2012.
 L. Changjin, X. Dehong, Z. Nan, F. Blaabjerg and Ch. Min, “DC-voltage fluctuation elimination through a DC-capacitor current control for DFIG converters under unbalanced grid voltage conditions,” IEEE Transactions on Power Electronics, vol. 28, no.7, pp. 3206-3218, 2013.
 J. Vidal, G. Abad, J. Arza and S. Aurtenechea, “Single-phase DC crowbar topologies for low voltage ride through fulfillment of high-power doubly fed induction generator-based wind turbines,” IEEE Transactions on Energy Conversion, vol. 28, no. 3, pp. 768-781, 2013.
 G. Pannell, B. Zahawi, D. J. Atkinson and P. Missailidis, “Evaluation of the performance of a DC-link brake chopper as a DFIG low-voltage fault-ride-through device,” IEEE Transactions on Energy Conversion, vol. 28, no. 3, pp. 535-542, 2013.
 M. Wang, W. Xu, H. Jia and X. Yu, “A new method for DFIG fault ride through using resistance and capacity crowbar circuit,” in Proceedings of the 2013 IEEE International Conference onIndustrial Technology, pp. 2004-2009, 2013.
 P. Cheng and H. Nian, “An improved control strategy for DFIG system anddynamic voltage restorer under grid voltage dip,” in Proceedings of the 2012 IEEE International Symposium onIndustrial Electronics, pp.1868 -1873, 2012.
 S. Zhang, K. J. Tseng, S. S. Choi, T. D. Nguyenand D. L. Yao, “Advanced control of series voltage compensation to enhance wind turbine ride through,” IEEE Transactions on Power Electronics, vol. 27, no. 2, pp. 763-772, 2012.
 P. S. Flannery and G. Venkataramanan, “Evaluation of voltage sag ride-through of a doubly fed induction generator wind turbine with series grid side converter,” in Proceedings of the IEEE Power Electronics Specialists Conference, pp. 1839-1845, 2007.
 V. Utkin, J. Guldner and J. Shi, “Sliding mode control in electromechanical systems,” London, U.K., Taylor and Francis, 1999.
V. Utkin, “Sliding mode control design principles and applications to electric drives,” IEEE Transaction on Industrial Electronics, vol. 40, no. 1, pp. 23-36, 1993.