An Adaptive Passivity-Based Control Plus Nonlinear Observer for Buck Converters with CPL Loads in DC Microgrids

This paper addresses the challenge posed by constant power loads (CPLs), which are known to induce negative impedances that can potentially destabilize DC microgrids (DCMGs). In this context, the paper introduces a control strategy tailored for buck converters operating within DCMGs, specifically designed to handle unknown CPLs. The proposed strategy integrates adaptive Passivity-Based Control (PBC) with an Extended Nonlinear Disturbance Observer (ENDO), aiming to enhance the controller's performance in existence of uncertainties and disturbances. For this aim, the ENDO refines the conventional Nonlinear Disturbance Observer (CNDO) to effectively mitigate CPL-induced instability and ensure the system's overall stability. The stability of the proposed controller is scrutinized through a comprehensive Lyapunov stability analysis, and its performance is benchmarked against existing methods. The proposed controller undergoes rigorous testing via simulation and experimentation to validate its effectiveness. This result shows that the proposed control approach ensures the stability of the system in different conditions including sudden changes in voltage references of converter, power of CPL, and input voltage of converter; furthermore, these results shows that overshoot and settling time of the PBC+ENDO are limited in the ranges of 1% and 1ms at their best condition, respectively. COPYRIGHTS © 2025 The author(s).