SMA SI 4548-US - Manual (Page 153)

SMA America, LLC 17 PV Inverters
Operating Manual SI4548-6048-US-BE-en-20 153
This completes the stand-alone grid parameter settings for the Sunny Boy.
17.5 Frequency-Shift Power Control (FSPC)
This section describes the operating principles of the "power adjustment via frequency" (Frequency
Shift Power Control - FSPC).
If Sunny Boy inverters are connected to the AC side of the off-grid system, the Sunny Island must be
able to limit their output power. This situation can occur when, e.g. the Sunny Island battery is fully
charged and the (solar) power available from the PV array exceeds the power required by the
connected loads.
To prevent the excess energy from overcharging the battery, the Sunny Island 4548-US / 6048-US
recognizes this situation and changes the frequency at the AC output. This frequency adjustment is
analyzed by the Sunny Boy. As soon as the power frequency increases and exceeds a defined value
"f
AC
Start Delta", the Sunny Boy limits its power accordingly.
This function is shown in the following figure:
5 Fac-max+
Upper range where the Sunny Boy is active,
based on f
0
Hz +3.0 (starting from the
base frequency f
0
)
6 dFac-Max
Max. rate of change Hz/s 4
7 Fac-start delta
Frequency increase in relation to f
0
, at which
point the power adjustment via frequency begins
Hz 1 (starting from the
base frequency f
0
)
8 Fac-Limit delta
Frequency increase based on f
0
, where the
power control via frequency ends. The power of
the Sunny Boy at this point is 0 W.
Hz 2 (starting from the
base frequency f
0
)
* V
AC Nom
= 208 V/240 V/277 V
No. Parameters Short descr. Value