Non-linear active disturbance rejection control for buck and boost DC/DC converters

DC power systems facilitate the efficient integration of converter-interfaced distributed energy resources (DER). This paper presents a voltage controller for the buck and boost DC/DC converters. A non-linear 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 and a Lyapunov feedback controller. The NL-ADRC model follows the generalised ADRC formulation, making the voltage controller applicable to converters of the non-minimum 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 employment 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 and a proportional error feedback controller. In addition, it offers good dynamic performance, stemming from the inherent properties of the employed 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 trade-offs in small and large-signal disturbances. The performance is analysed in simulations against both a PID controller and a L-ADRC model, and it is validated in hardware implementation in a lab set-up.