  Integrated with a high share of Inverter-Based Resources (IBRs), microgrids
face increasing complexity of frequency dynamics, especially after
unintentional islanding from the maingrid. These IBRs, on the other hand,
provide more control flexibility to shape the frequency dynamics of microgrid
and together with advanced communication infrastructure offer new opportunities
in the future software-defined microgrids. To enhance the frequency stability
of microgrids with high IBR penetration, this paper proposes an optimal
scheduling framework for software-defined microgrids to maintain frequency
stability by utilizing the non-essential load shedding and dynamical
optimization of the virtual inertia and virtual damping from IBRs. Moreover,
side effects of these services, namely, the time delay associated with
non-essential load shedding and potential IBR control parameter update failure
are explicitly modeled to avoid underestimations of frequency deviation and
over-optimistic results. The effectiveness and significant economic value of
the proposed simultaneous and dynamic virtual inertia and damping provision
strategy are demonstrated based on case studies in the modified IEEE 33-bus
system.
