IEEE Systems, Man and Cybernetics Magazine - April 2021 - 49

attack is detected, necessitating
that links be discarded to isolate
Information security
attacks. The main advantage of the
professionals
suggested resilient control is that
attacks are isolated in a distributed
regularly study
framework without possessing
methods to prevent
knowledge of whole systems. However, hackers may obtain switching
Economic Dispatching
attackers from
frequencies. Therefore, communiDistributed control approaches
accessing systems.
cation links must be periodically
are employed to maximize the
retuned to enhance system robusteconomic dispatching of grids.
They seldom consider
However, distributed structures
ness. Tests on two micro--grids demsituations where
make grids vulnerable to cyberatonstrate the strategy's performance
systems are under
tacks. Studying cyberattack effects
in detecting time-varying decepon distributed grid control has
tion attacks.
attack.
theoretical and practical merits
KF-based SE and feedback con[179]-[182]. An optimal economic
trol are developed in [193] for
dispatching method is presented
microgrids. A microgrid connected
in [183] for distributed generators. Each one estimates
to several DERs is modeled in a discrete linear state-space
its in-neighbors' incremental costs by using an observaframework with uncertainty and a cyberattack. A recurtion subnetwork. The estimates are harnessed to detersive systematic convolutional code is applied to provide
mine system misbehavior. Generators that are under
state redundancy. Following that, a log maximum posteriattack are identified by their out-neighbors. The main
or technique is adapted to estimate states from corrupted
advantage is that unaffected generators still have optimeasurements. Optimal feedback control is employed for
mal economic dispatching when a compromised generavoltage regulation. Simulations on a microgrid attached
tor is isolated. Simulations on an IEEE 123-bus system
to an IEEE four-bus system show that the control strucdemonstrate the approach's effectiveness. Liu et al. [184]
ture is efficient. Attack isolation and mitigation methods
present a preoverload vulnerability graph to detect load
are introduced in [194] for ac microgrids. A Kullback-
redistribution attacks in power grids. Such attacks are
Liebler divergence method is used in separate DERs to
often target security-constrained economic dispatch
compute a belief factor using Gaussian distributions and
data and lead to nonoptimal end even unsecure operatto detect deficiencies among neighboring DERs. A resiling conditions. The preoverload vulnerability graph evalient control strategy is proposed using the network's
uates system vulnerability in the presence of load
belief factors to mitigate attacks. Another resilient conredistribution attacks and calculates an index for varitrol framework is proposed in [195] for tolerating DoS
ous branches. The index can be used to detect malicious
attacks in microgrids. A rule-based fallback method is
events. Simulations on IEEE 118-bus, 39-bus, and Reliemployed to control frequency and voltage. A distributed
ability Test System-96 networks indicate that the stratestructure is constructed to manage DERs to mitigate DoS
gy enhances system security.
attacks. Test results on a 25-kV islanded microgrid indicate the strategy's efficiency.
Zuo et al. [196] develop a distributed control method for
Microgrid Control
ac
microgrids.
It is constructed to control voltage and freMicrogrids often provide efficient control frameworks to
quency. A resilient layer with hidden networks is added to
manage distributed energy resources (DERs). Generally,
an original physical layer to tolerate cyberattacks. Tests
microgrids consist of devices and communication netusing a controller/hardware-in-the-loop framework on an
works to control power networks and provide interactions
IEEE 34-bus system show that the controller is effective in
between nodes. Therefore, they are vulnerable to cyberatvarious attack scenarios. A hierarchical control approach
tacks [185]-[191]. Zhou et al. [192] develop a resilient conis proposed in [197] to compensate for the frequency and
trol structure to detect and tolerate strikes in a microgrid.
voltage of islanded microgrids exposed to cyberattacks.
Deception attacks are performed in a time-varying fashion
The hierarchical control framework consists of cyber and
on DER controllers and communication links. Microgrids
physical layers. The cyber layer is responsible for analyzemploy central master controllers to analyze DER data
ing communication data disturbance (CDD) effects. A
exchanges and adjust set points for participants. Data
combination of an extreme learning machine and an NN
exchanges between master controllers and DERs and
resolves the CDD. Droop control is applied in the physical
between individual DERs change periodically without
layer to regulate DER frequencies and voltages, and virtual
affecting normal operating conditions. The data exchange
leader-following consensus control is proposed to include
switching frequency is based on a predefined procedure. If
a time delay and provide secondary frequency and voltage
links' switching frequencies do not equal preset values, an
through an augmented Lagrangian
multiplier. Tests on synthetic PMU
data from a 16-machine, 68-bus
system indicate that the method
detects cyberattacks and accurately reconstructs original data.

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IEEE Systems, Man and Cybernetics Magazine - April 2021

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