  Distribution system state estimation (DSSE), which provides critical
information for system monitoring and control, is being challenged by multiple
sources of uncertainties such as random meter errors, stochastic power output
of distributed generation (DG), and imprecise network parameters. This paper
originally proposes a general interval state estimation (ISE) model to
simultaneously formulate these uncertainties in unbalanced distribution systems
by interval arithmetic. Moreover, this model can accommodate partially
available measurements of DG outputs and inaccurate line parameters. Further, a
modified Krawczyk-operator (MKO) algorithm is proposed to solve the general ISE
model efficiently, and effectively provides the upper and lower bounds of state
variables under coordinated impacts of these uncertainties. The proposed
algorithm is tested on unbalanced IEEE 13-bus and 123-bus systems. Comparison
with various methods including Monte Carlo simulation indicates that the
proposed algorithm is many orders of magnitude faster and encloses tighter
boundaries of state variables.
