SMA SUNNY CENTRAL CP XT Series - Power Control; Frequency-Dependent Active Power Limitation

10 Function Description
SMA Solar Technology AG
User Manual 93SCCPXT-E7-BA-en-58
If after approximately five minutes one of the errors 3501 ‒ Insulation Failure, 3504 ‒ Insulation failure ignored
or 3601 ‒ Warning insulation failure is displayed, the insulation is defective. In this case, a qualified person will
need to check and, if necessary, repair the insulation and then acknowledge the error.
Type of insulation monitoring device used
The insulation monitoring device used is the A-ISOMETERiso-PV1685 device supplied by BenderGmbH&Co.KG.
10.3 Power Control
10.3.1 Frequency-Dependent Active Power Limitation
With frequency-dependent active power limitation, the inverter 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 24: Power behavior of the inverter when the frequency limit P-HzStr is exceeded
If the power frequency exceeds a threshold defined in the parameter P‑HzStr, shown here at pointA, the inverter will
store 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 when the power
frequency falls below the threshold defined in the parameter P-HzStop, as 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, a minimum threshold for
power frequency shortfall can be defined with the parameter P-HzStopMin, shown here at pointD. If the power
frequency falls below the grid limit, the inverter will shut down and switch to the operating state "Grid monitoring". The
inverter will remain in the operating state "Grid monitoring" until all feed-in conditions are fulfilled again.
Calculation of the power limit:
P
max
= P
cur
‒ [(f
AC
‒ P-HzStr) · P-WGra · P
cur
]
P
max
Power limit P
cur
Current power