  Traditionally, a regional dispatch center uses the equivalent method to deal
with external grids, which fails to reflect the interactions among regions.
This paper proposes a distributed N-1 contingency analysis (DCA) solution,
where dispatch centers join a coordinated computation using their private data
and computing resources. A distributed screening method is presented to
determine the Critical Contingency Set (DCCS) in DCA. Then, the distributed
power flow is formulated as a set of boundary equations, which is solved by a
Jacobi-Free Newton-GMRES (JFNG) method. During solving the distributed power
flow, only boundary conditions are exchanged. Acceleration techniques are also
introduced, including reusing preconditioners and optimal resource scheduling
during parallel processing of multiple contingencies. The proposed method is
implemented on a real EMS platform, where tests using the Southwest Regional
Grid of China are carried out to validate its feasibility.
