Discrete-Time Fast Terminal Sliding Mode Control Design for DC-DC Buck Converters With Mismatched Disturbances

DC-DC converter systems have drawn extensive research attentions and shown upward tendencies for industrial and military applications. In this article, a novel digital fast terminal sliding mode control (FTSMC) approach is investigated for dc-dc buck converters with mismatched disturbances. Specifically, the approximated discrete-time model of the converters with multiple disturbances is first obtained and analyzed based on the Euler's discretization method. Then, by adopting the delayed estimation technique, it is easy to obtain the accurate estimations of the lumped disturbances. Integrating disturbance compensations into the modified digital fast terminal sliding mode surface, the proposed controller is finally constructed on the basis of equivalent control method and the performance analysis is presented. Both simulation and experimental comparisons are made for the proposed digital FTSMC approach and the existing discretized linear sliding mode controllers to validate the effectiveness and feasibility of the presented controller. The proposed FTSMC approach is characterized by higher voltage tracking accuracy and better dynamic properties in different operating conditions.