IEEE Power & Energy Magazine - May/June 2021 - 108

in my view

Dan Ton

microgrid protection
R&D to meet the challenges to come

THE DEDICATION OF AN ENTIRE
issue of IEEE Power & Energy Magazine
to microgrid protection is recognition of
the heightened importance of both microgrids and protection in the electric
power industry. The importance of microgrids is reflected in their ability to
enhance the resilience of critical facilities
against high-impact events, such as those
caused by extreme weather. These days,
microgrids often employ multiple distributed energy resources (DERs) from renewable energy sources, most commonly
solar in combination with storage. The
protection system is a critical component
of power system operation and responsible for identifying faults in the system
or microgrid and isolating them before
additional equipment is damaged. Microgrids are often connected to electric
power distribution networks and operated interactively with distribution utilities, making microgrid protection and
protection coordination with the main
grid increasingly complex. Another layer of protection complexity is added if
a microgrid is deployed on a secondary
distribution network.
Although the main function of microgrid protection is to isolate faults in
grid-connected or isolated modes, protection is also a key consideration for the
transition mode, transferring to/from
the connection to the utility. During the
transition, the compatibility and coordination of system protection devices are
critical; without them, the microgrid
would be in danger of collapsing.
Digital Object Identifier 10.1109/MPE.2021.3057972
Date of current version: 19 April 2021

108

ieee power & energy magazine

A major goal of the microgrid program has been to develop promising
new solutions to integrating microgrids
capable of
✔✔ operating in parallel with the utility distribution system
✔✔ transitioning seamlessly to an islanded power system
✔✔ operating safely and reliability
as islanded power systems.
Solutions for microgrid protection are
critical for this integration to take place.

Strategies for Microgrid
Protection in the
Microgrid Program
When the microgrid program developed
its strategy for advanced microgrids in
early 2011, five areas for R&D in microgrid protection were identified as
priorities. These areas are
1) the architecture of protection for
the emerging (smart) grid and
microgrids
2) new digital protective devices
and solutions
3) the integration of new, faster devices with existing slow devices
4) the design of the protection
schemes and the coordination of
all devices to meet the philosophy and objectives of smart grid
operations
5) the protection of the microgrid
in both grid-connected and islanded modes of operation and
the transition between operational modes.
Now, 10 years later, there has been
great progress in pursuing these re-

search priorities. These successes as
well as the emerging issues are summarized in the articles in this issue
of IEEE Power & Energy Magazine.
In most of the articles, the authors
discuss emerging issues and propose
some possible solutions for tackling
them. R&D to resolve these issues is
still very much a work in progress.
The contents of the articles show that
these research priorities remain valid
today for microgrid protection as both
the main grid and microgrids are seeing higher penetration of inverterbased DERs while facing an ever-growing need for resiliency.

Unique Protection
Requirements of Microgrids
Today, in microgrids as well as in distribution systems, major challenges
come from the high penetration of
inverter-based resources (IBRs) and
ever-changing microgrid configurations and controller designs. The microprocessor relays of the past must
be adapted to the needs of protecting
the microgrids as well as the distribution networks in systems with high
penetrations of IBRs. The starting
point for this adaptation in microgrids
begins with its unique protection requirements, which are different from
typical radial distribution protection requirements in four key ways.
1) Prevalence of power electronic
sources: Microgrids have significantly different time constants
(continued on p. 107)
may/june 2021

IEEE Power & Energy Magazine - May/June 2021

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