IEEE Electrification - December 2020 - 77

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Microgrid 1

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Microgrid 2
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Microgrid 3

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Figure 6. The modified IEEE 123-Node Test System with three microgrids highlighted.

may be fractal, there are significant
TABLE 1. The distributed energy resource data.
differences in how those requireGenerator Rating
Controller
ments are met. For example, the
Generator
(#)
Microgrid
(#)
Node
(#)
Type
(kVA)
Type
primary frequency response in a
microgrid can be achieved with
G1
1
50
Diesel
500
GGOV1
high-speed power electronics on a
G2
1
151
BESS
1,000
Grid-Forming
2-MW, grid-following unit, while
G3
2
197
Diesel
200
GGOV1
the bulk system could engage an
electromechanical actuator on a
G4
2
300
Diesel
100
GGOV1
600-MW thermal unit.
G5
2
105
PV
250
Grid-Following
The idealized distributed freG6
2
105
PV
250
Grid-Following
quency control shown in Figure 5
can be implemented using a disG7
3
72
Diesel
1,500
GGOV1
tributed multiagent system, implemented over an OpenFMB harness.
voltage source is not present; those in the nonshaded
The following section presents a simulated example of the
region cannot.
control response of the three-layer system in the presence
For this example, all three microgrids are initially operof an abnormal power-system event.
ating with the generation running in preparation for the
Simulation Example
occurrence of unintentional islanding-referred to as
The three-layer distributed frequency control of fractal
" storm mode " by some microgrid operators. In this condipower systems can be seen in the following simulated
tion, generators are typically running and loaded, batteries
example. For this article, a modified version of the
are being charged, and the system is in a condition where
IEEE 123-Node Test System with three microgrids is
a loss of the bulk power system would not result in the
used. Each has a combination of diesel generators and
loss of service to critical end-use loads (in this case, the
inverter-connected solar PV; the grid-following invertloads in the gray areas of Figure 6). The details of the DERs
ers are compliant with the IEEE Standard 1547-2018. In
are shown in Table 1.
Figure 6, the shaded regions represent the boundaries
Because the microgrids are being operated in storm
of the three microgrids. End-use loads in these regions
mode, the system transitions from the interconnected
can be supplied by the microgrids when the substation
condition of Figure 1(a) directly to those of Figure 1(c),
	

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

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IEEE Electrification - December 2020

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