A Hybrid Nonlinear Voltage Controller Design for DC-DC Buck Converters

This paper presents a hybrid non-linear voltage controller design approach for DC–DC buck converters where the hybridization is done by combining two non-linear techniques: backstepping and sliding mode. In the proposed hybrid framework, the backstepping approach ensures the tracking of all states, while the sliding mode scheme with an enhanced reaching law is utilized for the finite-time convergence of voltage and current in DC–DC buck converters. In this way, the proposed hybrid scheme offers two-degree freedom instead of one-degree in existing nonlinear approaches for controlling DC–DC converters, while guaranteeing the time-time convergence that is not achievable with existing methods in the same application. In this work, the sliding surface is modified to capture changes in the load and supply voltage and the Lyapunov stability theory is used to assess the overall stability of DC–DC buck converters with the proposed controller. Simulation and experimental validations are conducted for evaluating the performance of this hybrid scheme, including a comparative study of an existing sliding mode controller in which the sliding surface is selected as the fast terminal one while avoiding the non-singularity and incorporating the adaptation law.