  In this work, we propose a peer-to-peer secondary control for voltage and
frequency regulation in islanded microgrids to facilitate high inverter-based
distributed energy resource (DER) integration in the distribution grid. It has
been a major challenge to achieve various performance objectives simultaneously
in an inverter-driven microgrid, i.e., system frequency restoration, real power
sharing, voltage regulation and circulating var mitigation. We show that the
challenge can be addressed in even microgrids with 100% penetration of
inverters, without the support of any synchronous generators or the bulk power
system. In specific, we propose a novel control scheme to coordinate a fleet of
grid-forming and grid-following inverters by using a leader-follower consensus
algorithm to achieve these objectives simultaneously. Several use cases
examining the effects of microgrid switching events (topology change) and
communication degradation are presented to demonstrate the effectiveness of the
proposed control architecture.
