IEEE Electrification - December 2020 - 51

If a resident needs
to maintain a
controllable load,
the agents are
required to interfere
as minimally as
possible with his or
her decision.

The ILCs, equipped with intelligent
agents, and hence, communication
skills, interact with each other and
negotiate to decide which load will
be disconnected from the grid without a central decision by the MGCC.
In case there is lack of power, after
all noncritical loads are disconnected, the diesel is started.
One important feature of the
algorithm is the minimal disruption
of the residents' comfort, according
to their wishes. Therefore, if a resident needs to maintain a controllable load, the agents are required to
interfere as minimally as possible with his or her decision. On this account, the developed algorithm provides a token passed from one agent to another. When
an agent has the token, it is not allowed to operate its
noncritical loads (e.g., the water pump). The token is
passed from one agent to another in predefined time
intervals (e.g., 10 min). In this way, load shedding
does not burden only one house but is equally divided among the whole settlement. In case more than
one load needs to be disconnected, an additional
" digital baton " is created, following the aforementioned cyclic behavior.
Finally, regarding the energy shift, the system allows the
operation of the loads when it detects a frequency over
51 Hz (or SoC > 90%). According to the main principle of the
islanded operation of the system, when the batteries are
full the system increases the frequency and limits the production of the PV inverters. So, a high frequency is a strong

indication that the system rejects
energy production.
During the installation in the Kythnos Microgrid, a Wi-Fi Internet connection was established to allow
remote control through a virtual private network. As a result, commands
can be sent and data can be
exchanged among the ILCs, the
MGCC, and authorized users who are
not required to be on site. It should be
noted that an ILC communicates with
the MGCC through the LAN and Wi-Fi
interface they both feature (Figure 13).
Figure 14 presents a graphic of the
user interface of the software. It should be noted that
most citizens accepted the system well and were very
cooperative during the tests. This was aided by the public display of Figure 14 that demonstrated online the
concept of collaboration among the ILCs agents via message exchange.

Upgrade of the Kythnos Microgrid
Most DERs in the Kythnos Microgrid have been operating
for many years and are reaching the end of their useful
lives. An equipment upgrade is currently being considered
in the framework of the national " Kythnos Smart Island "
project, including an increase in its power and energy
capacity, which would allow the residents to use more
electrical appliances on their premises.
One of the major challenges in this upgrade is the
proper sizing of the equipment, not only in terms of cost
but also in reliability. For the financial comparison of

House 1

House 2

House N

MGC Communications
Server
System House
Figure 13. An overview of the communication system.

IEEE Elec trific ation Magazine / D EC EM BE R 2 0 2 0

IEEE Electrification - December 2020

Table of Contents for the Digital Edition of IEEE Electrification - December 2020