  Smart programmable microgrids (SPM) is an emerging technology for making
microgrids more software-defined and less hardware-independent such that
converting distributed energy resources (DERs) to networked community
microgrids becomes affordable, autonomic, and secure. As one of the
cornerstones of SPM, this paper pioneers a concept of software-defined
operation optimization for networked microgrids, where operation objectives,
grid connection, and DER participation will be defined by software and
plug-and-play, and can be quickly reconfigured, based on the development of
modularized and tightened models and a novel asynchronous price-based
decomposition-and-coordination method. Key contributions include: (1) design
the architecture of the operational optimization of networked microgrids which
can be readily implemented to ensure the programmability of islanded microgrids
in solving the distributed optimization models, (2) realize a novel discrete
model of droop controller, and (3) introduce a powerful distributed and
asynchronous method Distributed and Asynchronous Surrogate Lagrangian
Relaxation (DA-SLR) to efficiently coordinate microgrids asynchronously. Two
case studies are tested to demonstrate the efficiency of developed DA-SLR, and
specifically, the testing results show the superiority of DA-SLR as compared to
previous methods such as ADMM.
