<p>In order to solve the problem that the fault of wind energy conversion system is difficult to be detected, a new reaching law is proposed for the design of sliding mode observer (SMO) and sliding mode controller (SMC) in this paper, which can effectively detect and suppress system faults. Firstly, the finite time accessibility, stability and robustness of the Sliding Mode Observation System are analyzed theoretically. Compared with the traditional exponential reaching law, it not only ensures that the system state can quickly approach the sliding mode surface, but also quickly eliminates system chattering. Secondly, the SMO and SMC are constructed according to the mathematical model of doubly fed induction generator (DFIG), and their Lyapunov stability is proved. Finally, simulation experiments are carried out for different faults of DFIG. By comparing the measured rotor current with the observed value, the fault detection of DFIG is realized, and the accurate tracking ability of SMO and the good suppression effect of SMC are verified.</p>