Chattering free fractional-order sliding mode control for a buck converter based on an extended state observer: design, analysis and experiments

This paper presents a fractional-order non-singular terminal sliding mode control (SMC), based on an extended state observer (ESO) to mitigate load resistance disturbances in the buck converter. First, a novel modelling method is developed to convert the matched and mismatched disturbances caused by load resistance variations into a uniform matched total disturbance. An extended state observer is then designed to estimate and compensate the system state variables and total disturbance. Second, to overcome the issues of slow convergence and chattering phenomenon in traditional sliding mode control, a fractional-order non-singular terminal sliding mode control method is designed to achieve stable tracking of the reference voltage. Third, the stability of the closed-loop system is proved by Lyapunov theorem. Finally, both simulation and experimental results show that the proposed fractional-order SMC exhibits excellent voltage tracking performance and effective rejection of load disturbances.