Voltage Control of DC Microgrids: Robustness for Unknown ZIP-Loads

In this letter we propose a new passivity-based control technique for Buck converter based DC microgrids comprising ZIP-loads, i.e., loads with the parallel combination of constant impedance (Z), current (I) and power (P). More precisely, we propose a novel passifying input and a storage function based on the mixed potential function introduced by Brayton and Moser, relaxing restrictive (sufficient) conditions on Z, P and the voltage reference, which are usually assumed to be satisfied in the literature. Consequently, we develop a new passivity-based controller that is robust with respect to uncertain ZIP-loads.