SMA SI 4548-US - Manual (Page 154)

17 PV Inverters SMA America, LLC
154 SI4548-6048-US-BE-en-20 Operating Manual
The different settings have the following meanings:
• f
0
refers to the base frequency of the stand-alone grid created by the Sunny Island.
• f
AC
Delta– and f
AC
Delta+ refer to the maximum range in which the Sunny Boy is active, based
on, e.g. f
0
, 60 Hz.
• f
AC
Start delta refers to the frequency increase relative to f
0
, at which point the frequency shift
power control begins
• f
AC
Limit delta refers to the frequency increase relative to f
0
, at which point the frequency shift
power control stops. The power of the Sunny Boy at this point is 0 W.
If the thresholds "f
AC
Delta–" is fallen below or if "f
AC
Delta+" is exceeded, the Sunny Boy inverters
disconnect from the stand-alone grid.
When FSPC is activated and the diesel generator in the off-grid power system is operating, the diesel
generator determines the frequency, and the Sunny Boys react to certain changes in the diesel
generator frequency. The diesel generators generally operate at 60 Hz under load. For this reason,
in most cases the Sunny Boy inverters will deliver their entire power to the stand-alone grid, even when
the generator is in operation.
Short-term increase of the frequency possible
If the current battery voltage (V
Bat
) is greater than the nominal battery voltage (V
Bat, nom
) and is
also to be synchronized with an external source (generator), the Sunny Island temporarily
increases the frequency and disconnects the Sunny Boy inverters using the frequency shutdown
method (overfrequency). Afterwards, it synchronizes with the generator.