Cascade sliding mode control based on extended state observer method for a DC-DC buck converter

A cascade sliding mode control (CSMC) based on extended state observer (ESO) is proposed for a pulse width modulation based DC-DC buck converter system subject to disturbances in this paper. First, a novel tracking error state space model is introduced to define the matched and mismatched disturbances as a uniform matched disturbance. Second, an extended state observer is designed to estimate the system states and total disturbances, including load disturbances and input voltage variation. Third, the novel cascade sliding mode controller is constructed for the DC-DC buck converter based on the estimate values. In addition, the detailed theoretical stability analysis of the proposed controller is analyzed by a Lyapunov stability criterion. Finally, compared with traditional sliding mode control based on ESO (SMC-ESO) method, simulation results show that the CSMC-ESO method not only has the advantage of easy parameter tuning, but also performs a better disturbance rejection ability.