SMA SI 3324 - Manual (Page 41)

SMA Technologie AG Frequency Shift Power Control (FSPC)
User Manual SI3324/4248-14:FE2406 Page 41
7 Frequency Shift Power Control (FSPC)
This section describes how the power adjustment via frequency "Frequency Shift
Power Control (FSPC)" functions.
If Sunny Boy inverters are connected to the AC output side of a stand-alone grid, the
Sunny Island 3324/4248 must be able to limit their output power. This situation can
occur when (e.g.) the Sunny Island 3324/4248 batteries are fully charged and the
(solar) power available from the PV generator exceeds the power required by the
connected loads.
To prevent the excess energy from overcharging the batteries, the Sunny Island
3324/4248 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 frequency increase is 5 Hz maximum, starting at the nominal frequency f
0
.
When FSPC is activated and the generator is operating in the stand-alone grid, the
generator determines the frequency and the Sunny Boys react to changes in the
generator frequency. Generators normally operate at 50 Hz under load. For this
reason, in most cases the Sunny Boys will deliver their entire power to the stand-alone
grid, even when the generator is running.