Sunny Island 4500
Installation & Operating Instructions
BWRI45-13-EE0304
- 19 -
SMA Regelsysteme GmbH
2.1.3 Droop-mode operation (RUN_U, RUN_UEXT)
The droop mode allows to connect several Sunny Islands (each provided with its own
battery) in parallel, even though each Sunny Island will act as a grid-forming device.
Such a system will behave in many respects similarly to the large public electric util-
ity:
Fig. 2.3:
Frequency vs. load characteristics
If the available power on the AC bus of the system is higher than the power de-
manded, all Sunny Islands will charge their batteries and let the AC frequency slightly
rise, analog to the amount of energy stored in their batteries.
If the available power is less than the power demanded, the missing amount will be
fed into the AC bus by the Sunny Islands, slightly reducing the AC frequency.
Fig. 2.4:
Voltage vs. reactive power characteristics