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3. Possible Solutions for Flexible Power Control of PV Systems 211
3. POSSIBLE SOLUTIONS FOR FLEXIBLE POWER CONTROL
OF PV SYSTEMS
To realize a wide-scale adaptation of grid-connected PV system, the above grid inte-
gration issues need to be addressed. Therefore, solutions for flexible power control
of PV system are demanded. Various solutions to provide the power control flexi-
bility have been introduced for grid-connected PV systems. In this section, an over-
view of the widely used solutions to achieve flexible active power control
functionalities will be presented.
3.1 INTEGRATING ENERGY STORAGE SYSTEMS
Among other possible solutions, integrating PV systems with the energy storage sys-
tem (ESS) is one of the most widely used approaches [22e25]. For example, the bat-
tery technology is considered to be a suitable technology to be used with PV system
because of its high energy density and high efficiency. This solution has been adop-
ted with commercial PV systems, and it is commonly referred to as the PV-battery
system. In this combination, the extracted PV power from the PVarrays always fol-
lows the maximum available power, which fluctuates dynamically according to the
solar irradiance and ambient temperature conditions. However, the flexibility of the
power injection can be provided by the ESS, where the battery is charged and dis-
charged following the active power demand. Fig. 6.2 demonstrates the control strat-
egy of the PV system with integrated ESS.
One strong benefit of this solution is the increase of the PV energy utilization,
where the surplus PV power (e.g., during the PLC) can be stored in the battery
and used later during the low PV power production. This offers a possibility to pro-
vide an upward frequency regulation during the power reserve when the PV systems
are requested to inject the output power higher than the maximum available PV po-
wer production, which is achieved by discharging the battery.
FIGURE 6.2
Flexible active power control solution for grid-connected photovoltaic system by
integrating energy storage systems.
