Robust stability analysis of DC microgrids with constant power loads
  This paper studies stability analysis of DC microgrids with uncertain
constant power loads (CPLs). It is well known that CPLs have negative impedance
effects, which may cause instability in a DC microgrid. Existing works often
study the stability around a given equilibrium based on some nominal values of
CPLs. However, in real applications, the equilibrium of a DC microgrid depends
on the loading condition that often changes over time. Different from many
previous results, this paper develops a framework that can analyze the DC
microgrid stability for a given range of CPLs. The problem is formulated as a
robust stability problem of a polytopic uncertain linear system. By exploiting
the structure of the problem, we derive a set of sufficient conditions that can
guarantee robust stability. The conditions can be efficiently checked by
solving a convex optimization problem whose complexity does not grow with the
number of buses in the microgrid. The effectiveness and non-conservativeness of
the proposed framework are demonstrated using simulation examples.
