Grid; Voltage And Frequency Limits; Starting The Sunny Island; Operation During Grid Loss In Grid-Tied Backup Configuration - SMA SUNNY ISLAND 5048-US Technical Description

SMA America, LLC
14.2 Grid
The Sunny Island supports the operation of grid backup systems. Here, a distinction is made between
two main states: either a main power grid and an off-grid power system are connected or a main
power grid and an off-grid power system are disconnected. The operating mode of the Sunny Island
is derived from this. If the off-grid power system is disconnected, the Sunny Island alone is responsible
for powering this off-grid power system. If the main power grid is connected to the off-grid power
system, the off-grid power system is powered from the main power grid. The voltage and frequency
in the off-grid power system and in the main power grid are identical.
Operating Mode "Grid Feed"
Under specific conditions, the system can also temporarily feed energy from the off-grid
power system into the main power grid in the GridCharge operating mode
("232.08 GdMod" parameter).
14.2.1 Voltage and Frequency Limits
In order to operate on the grid, very strict limits (for voltage and frequency) must generally be
maintained. These strict limits are not sensible for generator operation. The limits are therefore set
separately for grid operation and the generator limits are not used.
Default Settings
The default settings for limits during grid operation comply with the following standards:
• For 120V_60Hz: UL1741
14.2.2 Starting the Sunny Island
The Sunny Island always starts in off-grid operation. Once the device is operating, it checks for the
presence and validity (voltage and frequency) of the external grid.
14.2.3 Operation During Grid Loss in Grid-Tied Backup
Configuration
In this scenario, when the utility grid is down, the Sunny Island supplies the demands of the protected
loads panel. At the same time the Sunny Island serves as the voltage source for Sunny Boy inverters
or any other grid-compatible current sources.
If the supply of energy of the current sources like Sunny Boy inverters exceeds the demands of the
protected loads panels, the excess will be used by the Sunny Island to charge the batteries.
14.2.4 Backup Operation and "Anti-Islanding"
In general, Sunny Boy inverters in backup systems are working for feeding energy into the public 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 tells the Sunny Boy that the Sunny Island is active
and monitors the public grid.
Technical Description
Connecting External Sources
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