SMA Solar Technology America LLC 14 Connecting External Sources
Operating Manual SI4548-6048-US-BE-en-21 131
14.2.2 Starting the Sunny Island
The Sunny Island always starts in stand-alone mode. Once the device is operating, it checks for the
presence and validity (voltage and frequency) of the utility grid.
14.2.3 Operation in Case of a Grid Failure in a Battery-Backup Grid
If the utility grid fails, the Sunny Island supplies the requirements of the protected load switch. At the
same time the Sunny Island serves as the voltage source for Sunny Boy inverters or any other
grid-compatible power source.
If the supply of energy from the power source exceeds the requirements of the protected load
switches, the energy surplus will be used by the Sunny Island to charge the batteries.
14.2.4 Battery-Backup Operation and Anti-Islanding
In general, Sunny Boy inverters in battery-backup systems feed in energy into the utility grid.
According to UL1741 an anti-islanding has to be active. During normal operation, the Sunny Island
performs this verification. The battery inverter is connected to the Sunny Boy via a CAT5 cable using
a RS485 communication. This communication line signals the Sunny Boy that the Sunny Island is
active and monitors the utility grid.
Whenever this information is missing (in the event of maintenance or interference) the Sunny Boy
inverters switch from the "OffGrid" setting to the "grid tied" setting and take on the anti-islanding
function. This ensures that an anti-islanding is active at all times according to UL1741 when feeding
into the utility grid.
If the Sunny Island continues working, it orders the Sunny Boy inverters to switch back to the "OffGrid"
setting and performs the anti-islanding.
This function can be realized with the Sunny Island inverters in combination with the compatible PV
inverters. You will find the list with compatible PV inverters in the download are at
www.SMA-America.com in the Technical Information "PV Inverters: Use of PV Inverters in Off-Grid
Systems and Battery-Backup Systems North America and South America".
RS485 Piggy-Backs must be installed in both the Sunny Island and in the Sunny Boy inverters. In
addition, a CAT5 cable is needed.
Default values
The default values for limits during grid operation comply with the following standards:
• For 120 V_60 Hz: UL1741
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