A Robust Controller Based on High-Order Fully Actuated Approach for DC–DC Buck Converter With Constant Power Loads in DC Microgrids

The negative incremental impedance characteristics exhibited by constant power loads (CPLs) in dc microgrids introduce instability in upstream dc–dc buck converters. In this article, a robust control strategy based on high-order fully actuated system approach is proposed for globally stabilizing and regulating the buck converter feeding CPLs. First, a second-order fully actuated model incorporating nonlinear uncertainties from input, load and system parameters disturbances is derived to describe system dynamics. A robust control law is then synthesized from the perspective of second-order system dynamics by compensating for the negative effects introduced by CPLs and reconstructing the desired closed-loop dynamics through first-order state feedback. Second, an uncertainty boundary estimator is designed to enhance system robustness against disturbances without precise measurements of load or input. A simple differential state observer is adopted to avoid the use of noise-sensitive differentiators. The proposed controller not only ensures large signal stability of the system, but also achieves accurate tracking and fast dynamic response within a wide working range. Simulations and experiments are further conducted to validate the effectiveness and superiority of the presented controller.