  Recovery of power flow to critical infrastructures, after grid failure, is a
crucial need arising in scenarios that are increasingly becoming more frequent.
This article proposes a power transition and recovery strategy by proposing a
mode-dependent droop control-based inverters. The control strategy of inverters
achieves the following objectives 1) regulate the output active and reactive
power by the droop-based inverters to a desired value while operating in
on-grid mode 2) seamless transition and recovery of power flow injections into
the critical loads in the network by inverters operating in off-grid mode after
the main grid fails; 3) require minimal information of grid/network status and
conditions for the mode transition of droop control. A framework for assessing
the stability of the system and to guide the choice of parameters for
controllers is developed using control-oriented modeling. A comprehensive
controller hardware-in-the-loop-based real-time simulation study on a
test-system based on the realistic electrical network of M-Health Fairview,
University of Minnesota Medical Center, corroborates the efficacy of the
proposed controller strategy.
