Extended State Observer based Nonsingular Terminal Sliding Mode Controller for a DC-DC Buck Converter with Disturbances: Theoretical analysis and experimental verification

This paper develops a continuous nonsingular terminal sliding mode controller (NTSMC) based on extended state observer (ESO) method for a DC-DC buck converter subject to both load disturbances and input voltage variations. First, a novel modeling method based on output feedback is developed to transform the matched and mismatched disturbances caused by load resistance and input voltage variations of the DC-DC buck converter into a uniform matched total disturbance. Second, a three-order ESO is established to estimate and compensate the differential of the output voltage and the total disturbance including the load disturbances and input voltage variation. Third, a nonsingular terminal sliding mode control based on the estimated values is designed to achieve faster tracking speed and better tracking accuracy around the expected voltage. In addition, the theoretical stability of the proposed controller is analyzed in detail by a Lyapunov stability criterion. Finally, both comparative simulation and experimental results show that the proposed NTSMC-ESO controller with the novel modeling method can attenuate the input voltage variation effectively and has a better load disturbance rejection ability than the conventional reduced-order ESO based sliding mode control method.