  The presence of constant power loads (CPLs) in dc shipboard microgrids may
lead to unstable conditions. The present work investigates the stability
properties of dc microgrids where CPLs are fed by fuel cells (FCs), and energy
storage systems (ESSs) equipped with voltage droop control. With respect to the
previous literature, the dynamics of the duty cycles of the dc-dc converters
implementing the droop regulation are considered. A mathematical model has been
derived, and tuned to best mimic the behavior of the electrical representation
implemented in DIgSILENT. Then the model is used to find the sufficient
conditions for stability with respect to the droop coefficient, the dc-bus
capacitor, and the inductances of the dc-dc converters.
