  Distributed cooperative droop control consisting of the primary decentralized
droop control and the {secondary} distributed correction control is studied in
this paper, which aims to achieve an exact current sharing between generators,
worked in the voltage control mode, of DC microgrids. For the DC microgrids
with the distributed cooperative droop control, the dynamic stability has not
been well investigated although its steady performance has been widely
reported. This paper focuses on the stability problem and shows it is
equivalent to the semistability problem of a class of second-order matrix
systems. Some further sufficient conditions as well followed. The steady state
is analyzed deeply for some special cases. A DC microgrid of three nodes is
simulated on the Matlab/Simulink platform to illustrate the efficacy of
analytic results.
