Nonlinear Active Disturbance Rejection Control for Buck and Boost DC/DC Converters

DC power systems facilitate efficient integration of converter-interfaced distributed energy resources (DERs). This article presents a voltage controller for the buck and boost dc/dc converters. A nonlinear active disturbance rejection control (NL-ADRC) model is proposed, consisting of an augmented sliding-mode observer for the state and disturbance estimation, an adaptive reference trajectory generator (RTG), and a Lyapunov feedback controller. The NL-ADRC model follows the generalized ADRC formulation, making the voltage controller applicable to converters of the nonminimum-phase (NMP) class and suitable for matched and mismatched disturbances, opposite to the original ADRC formulation, applied mostly in converters. The formulation of the reference trajectory of the NL-ADRC model according to the estimated disturbance provides a smooth state reference to the state feedback controller and enhances the robustness of the voltage controller against disturbances. The use of advanced estimation and feedback control methods provides more degrees of freedom in the control design than the common L-ADRC model with a Luenberger extended state observer (ESO) and a proportional error feedback controller. In addition, it offers good dynamic performance, stemming from the inherent properties of the used methods. The NL-ADRC model is designed based on both frequency- and time-domain analyses, contrary to the design approaches of ADRC converter controllers in literature, revealing design tradeoffs in small- and large-signal disturbances. The performance is analyzed in simulations against both a PID controller and an L-ADRC model, and it is validated in hardware implementation in a laboratory setup.