SMA Solar Technology AG
8 Power Control
User Manual
SCCP-JP-BA-A4-en-12
49
8 Power Control
8.1 Active Power Limitation
8.1.1 Frequency-Dependent Active Power Limitation
8.1.1.1 Principle of Frequency-Dependent Active Power Limitation
For active power limitation based on power frequency, the Sunny Central constantly checks the connected power
frequency. If the active power is to be limited by a hysteresis, the parameter
WCtlHzMod
must be set to
CurveHys
.
Figure 18: Behavior of the Sunny Central when the P-HzStr frequency limit is exceeded
If the power frequency exceeds a threshold defined in the parameter
P
-
HzStr
, shown here at point A, the Sunny Central
will save the current feed-in power P
cur
. The reduced feed-in power is calculated based on this saved value. The reduction
of the feed-in power is defined via the parameter
P-WGra
. This parameter indicates the percentage of the saved power
P
cur
by which the power per Hz will be reduced if the power frequency continues to rise.
If the power frequency decreases again as shown in point B, the last feed-in power value reached will remain valid.
Only once the power falls below the threshold defined in the parameter
P-HzStop
, shown here at point C, can the feed-in
power be increased again. In this case, the saved value P
mom
forfeits its validity. In addition, it is possible to define a
minimum power frequency threshold, shown here at point D, using the parameter
P-HzStopMin
.
Once the power frequency exceeds the grid limit, the Sunny Central will shut down and switch to the operating state
"Grid monitoring". The Sunny Central remains in the operating state "Grid monitoring" until all feed-in conditions are met
again.
Calculating the power limit:
P
max
Power limit
P
cur
Current power
f
AC
Power frequency
P-WGra
Gradient for reducing active power
P-HzStr
Selected frequency limit from which
feed-in power will be reduced
P
max
P
mom
f
AC
P-HzStr
–
P-WGra
P
mom
–
=
