IEEE Electrification Magazine - June 2017 - 59
Adaptive Protection:
Guaranteed Safe Operation
of Islanded Microgrids
The microgrid protection scheme
plays a significant role in ensuring
its safe operation. Because of the
different operation modes and vari-
ous types of DERs, the protection
scheme in microgrids is not the
same as that in conventional dis-
tribution systems. The protection
scheme in conventional distribution
systems mainly relies on protective
Solar Irradiation (Wh/m2)
the investment cost, operation and maintenance cost, out-
put power degradation rate, operation curve with respect
to different irradiation and temperature conditions, and
energy conversion efficiency, among other variables. Mean-
while, solar irradiation imposes inevitable intermittency, as
shown in the typical daily solar irradiation curve (sunrise
to sunset) in Figure 3. This also should be considered when
modeling the stochastics of PV panels.
In addition to the basic requirements with respect to
the balance in electrical and thermal systems, the plan-
ning of remote microgrids may also consider advanced
constraints to guarantee that the designed microgrid has
sufficient generation reserve to ensure secure operation
with the loss of a single unit. This requires the integration
of additional constraints in the optimization problem to
guarantee the N − 1 or even N − m contingency. As men-
tioned previously, with the integration of intermittent
DERs, the power balance in remote microgrids might be
violated. For example, stochastic solar irradiation and
ambient temperature can significantly influence the out-
put power of PV panels. Furthermore, for operation at
night, the PV panels are incapable of supporting any active
power. This intermittency induces power variations and
may lead to frequency and voltage instability due to the
mismatch between source and load power. To mitigate
intermittency, energy storage systems (ESSs) need to be
deployed. There are different types of ESUs that can be
used in remote microgrids. Among them, battery storage
systems are the most common type of storage. Hybrid
ESSs are also frequently used in remote microgrids to
leverage the capabilities of different types of storage.
In recent research, some emergent types of ESUs
have been studied. Among them, compressed air energy
storage (CAES) features high capacity and fast dynamic
responses, including high ramp-up rate and startup
time. Hence, it has been intensively studied in microgrid
planning. A typical configuration of CAES is shown in
Figure 4, which includes the main components of the
compressor, expander, air container, and other compo-
nents. The capacity rating of CAES is determined by the
size of the air container, whereas the power rating of
CAES is determined by the compressor and expander.
800
600
400
200
0
6 7
8
9 10 11 12 13 14 15 16 17 18 19
Hour (Sunrise to Sunset)
Figure 3. Typical daily solar irradiation.
devices (e.g., reclosers, sectionalizers, and fuses). Among
them, most of the devices that are capable of interrupting
fault current are designed on the basis of programmable
time-current curves. For example, reclosers, which are
series connected to the sectionalizers, follow the program-
mable time-current curve to determine the threshold for
cutting off the fault sections, whereas fuses follow the
fixed time-current curve to determine the blow-out cur-
rent. These devices are used as the units in conventional
distribution systems to conduct the protective strategies.
However, the operation of a microgrid requires an adaptive
protection scheme. This can be addressed in two ways.
First, because the conventional distribution system is
essentially a passive network, the power flow follows a
single direction from the main feeder to the end users.
Hence, traditional protective devices are only designed to
detect uni-directional fault current and are not capable of
sensing fault current in the reverse direction. Because the
penetration of DERs makes a microgrid an active system,
conventional protective devices designed for detecting
uni-directional fault current may cause protection mal-
function, which requires a new type of protective device
that adapts to a bidirectional fault current.
Second, in conventional distribution systems, the sole
contributor to the fault current is the main feeder, which is
interconnected to the transmission system, whereas in a
microgrid, various types of sources should be considered.
Rather than only relying on the power feeding in via the
point of common coupling (PCC), a microgrid is also
Compressor
Expander
Air
Motor
Container
Heat
Heat
Exchanger
Exchanger
Air
Intake
Cold Fluid
Tank
Generator
Air
Discharge
Hot Fluid
Tank
Figure 4. A typical configuration of CAES.
IEEE Electrific ation Magazine / j une 2 0 1 7
59
Table of Contents for the Digital Edition of IEEE Electrification Magazine - June 2017
IEEE Electrification Magazine - June 2017 - Cover1
IEEE Electrification Magazine - June 2017 - Cover2
IEEE Electrification Magazine - June 2017 - 1
IEEE Electrification Magazine - June 2017 - 2
IEEE Electrification Magazine - June 2017 - 3
IEEE Electrification Magazine - June 2017 - 4
IEEE Electrification Magazine - June 2017 - 5
IEEE Electrification Magazine - June 2017 - 6
IEEE Electrification Magazine - June 2017 - 7
IEEE Electrification Magazine - June 2017 - 8
IEEE Electrification Magazine - June 2017 - 9
IEEE Electrification Magazine - June 2017 - 10
IEEE Electrification Magazine - June 2017 - 11
IEEE Electrification Magazine - June 2017 - 12
IEEE Electrification Magazine - June 2017 - 13
IEEE Electrification Magazine - June 2017 - 14
IEEE Electrification Magazine - June 2017 - 15
IEEE Electrification Magazine - June 2017 - 16
IEEE Electrification Magazine - June 2017 - 17
IEEE Electrification Magazine - June 2017 - 18
IEEE Electrification Magazine - June 2017 - 19
IEEE Electrification Magazine - June 2017 - 20
IEEE Electrification Magazine - June 2017 - 21
IEEE Electrification Magazine - June 2017 - 22
IEEE Electrification Magazine - June 2017 - 23
IEEE Electrification Magazine - June 2017 - 24
IEEE Electrification Magazine - June 2017 - 25
IEEE Electrification Magazine - June 2017 - 26
IEEE Electrification Magazine - June 2017 - 27
IEEE Electrification Magazine - June 2017 - 28
IEEE Electrification Magazine - June 2017 - 29
IEEE Electrification Magazine - June 2017 - 30
IEEE Electrification Magazine - June 2017 - 31
IEEE Electrification Magazine - June 2017 - 32
IEEE Electrification Magazine - June 2017 - 33
IEEE Electrification Magazine - June 2017 - 34
IEEE Electrification Magazine - June 2017 - 35
IEEE Electrification Magazine - June 2017 - 36
IEEE Electrification Magazine - June 2017 - 37
IEEE Electrification Magazine - June 2017 - 38
IEEE Electrification Magazine - June 2017 - 39
IEEE Electrification Magazine - June 2017 - 40
IEEE Electrification Magazine - June 2017 - 41
IEEE Electrification Magazine - June 2017 - 42
IEEE Electrification Magazine - June 2017 - 43
IEEE Electrification Magazine - June 2017 - 44
IEEE Electrification Magazine - June 2017 - 45
IEEE Electrification Magazine - June 2017 - 46
IEEE Electrification Magazine - June 2017 - 47
IEEE Electrification Magazine - June 2017 - 48
IEEE Electrification Magazine - June 2017 - 49
IEEE Electrification Magazine - June 2017 - 50
IEEE Electrification Magazine - June 2017 - 51
IEEE Electrification Magazine - June 2017 - 52
IEEE Electrification Magazine - June 2017 - 53
IEEE Electrification Magazine - June 2017 - 54
IEEE Electrification Magazine - June 2017 - 55
IEEE Electrification Magazine - June 2017 - 56
IEEE Electrification Magazine - June 2017 - 57
IEEE Electrification Magazine - June 2017 - 58
IEEE Electrification Magazine - June 2017 - 59
IEEE Electrification Magazine - June 2017 - 60
IEEE Electrification Magazine - June 2017 - 61
IEEE Electrification Magazine - June 2017 - 62
IEEE Electrification Magazine - June 2017 - 63
IEEE Electrification Magazine - June 2017 - 64
IEEE Electrification Magazine - June 2017 - 65
IEEE Electrification Magazine - June 2017 - 66
IEEE Electrification Magazine - June 2017 - 67
IEEE Electrification Magazine - June 2017 - 68
IEEE Electrification Magazine - June 2017 - 69
IEEE Electrification Magazine - June 2017 - 70
IEEE Electrification Magazine - June 2017 - 71
IEEE Electrification Magazine - June 2017 - 72
IEEE Electrification Magazine - June 2017 - 73
IEEE Electrification Magazine - June 2017 - 74
IEEE Electrification Magazine - June 2017 - 75
IEEE Electrification Magazine - June 2017 - 76
IEEE Electrification Magazine - June 2017 - 77
IEEE Electrification Magazine - June 2017 - 78
IEEE Electrification Magazine - June 2017 - 79
IEEE Electrification Magazine - June 2017 - 80
IEEE Electrification Magazine - June 2017 - 81
IEEE Electrification Magazine - June 2017 - 82
IEEE Electrification Magazine - June 2017 - 83
IEEE Electrification Magazine - June 2017 - 84
IEEE Electrification Magazine - June 2017 - 85
IEEE Electrification Magazine - June 2017 - 86
IEEE Electrification Magazine - June 2017 - 87
IEEE Electrification Magazine - June 2017 - 88
IEEE Electrification Magazine - June 2017 - Cover3
IEEE Electrification Magazine - June 2017 - Cover4
https://www.nxtbook.com/nxtbooks/pes/electrification_december2022
https://www.nxtbook.com/nxtbooks/pes/electrification_september2022
https://www.nxtbook.com/nxtbooks/pes/electrification_june2022
https://www.nxtbook.com/nxtbooks/pes/electrification_march2022
https://www.nxtbook.com/nxtbooks/pes/electrification_december2021
https://www.nxtbook.com/nxtbooks/pes/electrification_september2021
https://www.nxtbook.com/nxtbooks/pes/electrification_june2021
https://www.nxtbook.com/nxtbooks/pes/electrification_march2021
https://www.nxtbook.com/nxtbooks/pes/electrification_december2020
https://www.nxtbook.com/nxtbooks/pes/electrification_september2020
https://www.nxtbook.com/nxtbooks/pes/electrification_june2020
https://www.nxtbook.com/nxtbooks/pes/electrification_march2020
https://www.nxtbook.com/nxtbooks/pes/electrification_december2019
https://www.nxtbook.com/nxtbooks/pes/electrification_september2019
https://www.nxtbook.com/nxtbooks/pes/electrification_june2019
https://www.nxtbook.com/nxtbooks/pes/electrification_march2019
https://www.nxtbook.com/nxtbooks/pes/electrification_december2018
https://www.nxtbook.com/nxtbooks/pes/electrification_september2018
https://www.nxtbook.com/nxtbooks/pes/electrification_june2018
https://www.nxtbook.com/nxtbooks/pes/electrification_december2017
https://www.nxtbook.com/nxtbooks/pes/electrification_september2017
https://www.nxtbook.com/nxtbooks/pes/electrification_march2018
https://www.nxtbook.com/nxtbooks/pes/electrification_june2017
https://www.nxtbook.com/nxtbooks/pes/electrification_march2017
https://www.nxtbook.com/nxtbooks/pes/electrification_june2016
https://www.nxtbook.com/nxtbooks/pes/electrification_december2016
https://www.nxtbook.com/nxtbooks/pes/electrification_september2016
https://www.nxtbook.com/nxtbooks/pes/electrification_december2015
https://www.nxtbook.com/nxtbooks/pes/electrification_march2016
https://www.nxtbook.com/nxtbooks/pes/electrification_march2015
https://www.nxtbook.com/nxtbooks/pes/electrification_june2015
https://www.nxtbook.com/nxtbooks/pes/electrification_september2015
https://www.nxtbook.com/nxtbooks/pes/electrification_march2014
https://www.nxtbook.com/nxtbooks/pes/electrification_june2014
https://www.nxtbook.com/nxtbooks/pes/electrification_september2014
https://www.nxtbook.com/nxtbooks/pes/electrification_december2014
https://www.nxtbook.com/nxtbooks/pes/electrification_december2013
https://www.nxtbook.com/nxtbooks/pes/electrification_september2013
https://www.nxtbookmedia.com