Page 84 - IJOCTA-15-4

Viet Thanh et al. / IJOCTA, Vol.15, No.4, pp.625-648 (2025)
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role. This is supported by reports from the Ger- disturbance. It is automatically provided by the
man Federal Ministry for Economic Affairs and inertia of synchronous generators and motors di-
Energy. According to the National Energy Ad- rectly connected to the grid, which resist sud-
ministration, in 2023, renewable energy accounted den frequency changes. This control is also sup-
for approximately 30% of China’s total electric- ported by the speed governor systems. The sec-
ity capacity, with substantial contributions from ondary frequency control follows the PFC when
both wind and solar power. In the United States, a large frequency deviation persists for a longer
RESs contributed about 20% of total electricity period, typically between 30 and 1800 s. It is pro-
production, as reported by the United States En- vided by automatic generation control and man-
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ergy Information Administration. In Denmark, ual actions. The tertiary frequency control is an
over 50% of electricity was generated from wind emergency control strategy that must be imple-
energy in 2022, according to the Danish Energy mented if the frequency drops below the required
Agency. In Spain, wind and solar energy together threshold after a significant event. It requires an
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contributed about 30% to total electricity produc- optimal solution to restore stability. Therefore,
tion. India aimed to achieve 175 GW of renewable each stage corresponds to different time scales and
energy capacity in 2022, including 100 GW from transient phenomena, each requiring specific sup-
solar and 60 GW from wind, as reported by the port measures.
Spanish grid operator Red El´ectrica de Espa˜na.
In Turkey, the total electricity capacity reached Wind and solar power plants use inverters,
97.7 GW, with over 53% of it generated by RESs. 1 which lack the inertia characteristic of synchro-
nous generators. The variability of wind and solar
As the adoption of solar photovoltaic and
resources complicates the maintenance of supply-
wind energy increases, the reliance on fossil fu-
demand balance. Wind turbines, in particular,
els for electricity generation decreases, bringing
may experience higher errors when tracking the
both economic and ecological benefits. However,
voltage phase angle during faults, further com-
there are significant challenges and risks due to
plicating frequency regulation and stabilization.
the ongoing reconfiguration of power system oper- Traditionally, frequency control in systems with
ations. Consequently, the power system faces sta-
integrated renewable RESs has relied on thermal
bility challenges. Many of these RESs do not pro- 6
and hydropower plants. However, when a sub-
vide the same inertia as synchronous generators,
stantial amount of renewable energy and power
which reduces the system’s ability to maintain fre-
electronic equipment are integrated into the grid,
quency stability after a fault. Additionally, these
the power system exhibits weak damping and low
sources may struggle to provide stable reactive
inertia, making it difficult to maintain frequency
power, weakening voltage stability, and leading 7
stability. As a result, this conventional approach
to potential voltage problems. Furthermore, the
becomes less effective, leading to frequency fluc-
output from these renewable sources is weather- tuations that fall outside the permissible network
dependent, causing fluctuations in power gener- 8
ation and complicating prediction and control. frequency range.
The integration of multiple renewable sources also Battery energy storage systems (BESS) are
requires more complex management and control essential technologies for energy management and
systems to ensure coordination and optimization storage and are increasingly being proposed as
across the entire power system. a key alternative for frequency stabilization. In
A typical example of frequency fluctuations addition to the numerous benefits of BESS, such
caused by a generation outage of up to 1800 MW as enhancing frequency dynamics performance, 9
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is shown in Figure 1. The rate of change of fre- storing, and releasing energy over short periods, 10
quency (RoCoF) represents how quickly the fre- improving grid stability, reducing energy costs,
quency drops. RoCoF is directly proportional and providing backup power, 11 and selecting the
to the disturbance and inversely proportional to appropriate control method remains a significant
the system’s inertia constant. Maintaining the challenge. Numerous studies have focused on in-
load frequency at its nominal value is crucial to tegrating BESS with existing synchronous gen-
ensuring the safe and reliable operation of the erators to support automatic generation control
power system. Frequency regulation is achieved (AGC) and restore system frequency to its nom-
through primary frequency control (PFC), sec- inal value. For example, Xie et al. 12 proposed
ondary frequency control, and tertiary frequency the model predictive control method to optimize
control loops, depending on the frequency devi- BESS operation. The study presented experimen-
ation range. The PFC is a rapid-response con- tal or simulation results demonstrating that us-
trol loop that operates in the first 30 s after a ing BESS in AGC systems can greatly enhance
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