This paper presents a novel chattering-free sliding mode control method for a class of disturbed nonlinear systems, which achieves fast and exact disturbance estimation, eliminates chattering, and recovers the performance of nominal system and nominal control input. The proposed approach combines time scale separation design and sliding mode control. Different from the existing disturbance estimation based sliding mode control methods, the proposed scheme achieves fast and exact disturbance estimation through time scale separation and eliminates discontinuous switching term, thereby achieving good chattering alleviation effect and providing good transient response. The proposed control method is applied to suppress chaos in power system and simulation results confirm the effectiveness and robustness of proposed control scheme and highlight the advantages of the proposed control scheme over the existing disturbance estimation based sliding mode control methods in terms of chattering alleviation effect and transient response.