SMA Solar Technology AG Sunny Boy in the Island Grid System
Technical Description SI2012_2224-TEN082311 157
To prevent the excess energy from overcharging the batteries, the Sunny Island recognizes this
situation and changes the frequency of the AC output. This frequency adjustment is analyzed by the
Sunny Boy. As soon as the grid frequency increases beyond the value specified by "Fac-Start delta"
the Sunny Boy limits its output power accordingly.
This function is shown in the following figure:
The terms in the figure have the following meaning:
•f
0
refers to the base frequency of the stand-alone grid (here 50 Hz)
• Fac-delta– and Fac-delta+ refer to the max. range in which the Sunny Boy is active, based on
f
0
• Fac-start delta refers to the frequency increase relative to f
0
, at which point the power
adjustment via frequency begins.
• Fac-Limit delta refers to the frequency increase relative to f
0
, at which point the power
adjustment via frequency ends. The power of the Sunny Boy here is 0 W.
If the value is below the Fac-delta limit and/or above the Fac-delta+ limit, the Sunny Boys are
disconnected from the grid.
Sunny Boy Frequency Reduction
The Sunny Island reduces the frequency momentarily when it needs to synchronize itself
to the public grid and the present battery voltage (V
Batt
) is greater than the nominal
battery voltage (V
Batt soll
).
In this way it disconnects the Sunny Boys via this frequency reduction (excessive
frequency) and then synchronizes itself to the external source.
The Sunny Boys switch themselves on again automatically as soon as the grid frequency
is within the limit again.
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