Page 205 - Renewable Energy Devices and System with Simulations in MATLAB and ANSYS

192 Renewable Energy Devices and Systems with Simulations in MATLAB and ANSYS ®
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8.5.2 Solutions for Better Grid Support
The grid codes now have more strict regulations to the behaviors of the active and reactive power
of the WT outputs; some of the requirements could be difficult to be achieved by the individual WT
concept. However, at the wind farm level, more powerful grid support features can be relatively
easily achieved by introducing special power electronics equipment and control.
As mentioned before, most of the grid codes require active power control of the WTS to be flex-
ibly regulated based on the grid frequency. However, the output power of WTs should be based on
the current wind speeds. In order to achieve this advanced feature, some energy storage systems
may be needed for WTs and wind farms. The storage system can be configured locally for each WT
unit, as shown in Figure 8.15a, or be configured centrally for several WTs/wind farms, as shown
in Figure 8.15b. It is noted that the energy storage could be in the form of battery, supercapacitor,
flywheel, hydropower station, or even combined energy storage systems—again power electronics
is an enabling technology in these storage systems to manage the power flow. Such wind farm with

AC DC
DC AC

+ DC
– DC
Small energy
storage system
MVAC
AC DC
grid
DC AC
+ DC
– DC
Small energy
storage system
(a)

AC DC
DC AC

AC DC
DC AC MVAC
grid

Large energy DC
storage +
system – AC

(b)

FIGURE 8.15 Potential configurations of energy storage for wind power plants to achieve more controllable
active power output. (a) Distributed energy storage. (b) Centralized energy storage.