SMA SUNNY ISLAND 6.0H - Starting and Stopping the System; Switching on the Sunny Island; Starting the System

3 Functions and Design
SMA Solar Technology AG
System Description 17SI44M-80H-13-MC-IA-en-10
3.2.2 Structure for Systems with Increased Self-Consumption and Battery-
Backup Function
MAIN
CLUSTER
EXTENSION
CLUSTER 1
EXTENSION
CLUSTER 3
GRID-CONNECT-
BOX
MULTICLUSTER-BOX
GENERATOR
LOAD
PV SYSTEM
UTILITY GRID
Grid-connection point
with energy meter
of the
electric utility company
TN or TT system
Figure 5: Principle of a multicluster system with Multicluster-Box, GridConnect Box, utility grid, and generator
The Grid-Connect-Box enables the connection of an utility grid and a generator to one multicluster system. In doing so,
the Grid-Connect-Box may only be used where the VDE-AR-N4105 application guide for utility grids is not required.
If increased self-consumption is required, the multicluster system with Grid-Connect-Box must be configured via the
installation assistant for Grid mode.
3.3 Off-Grid System
3.3.1 Off-Grid System Functions
Multicluster systems set up as off-grid systems can form self-sufficient utility grids fed with energy from multiple AC
sources in the stand-alone grid (e.g. PV inverter) and from grid-forming AC sources (e.g. a generator). The
SunnyIsland forms the stand-alone grid as a AC voltage source. The SunnyIsland regulates the balance between the
energy that is fed in and the energy that is used and features a battery, PV array and load management system.
Battery Management
Exact determination of the state of charge is a basic requirement for the correct operation of lead-acid batteries.
The SunnyIsland battery management system for lead-acid batteries is based on an exact determination of the state of
charge. By combining the three most common methods for recording the state of charge, the SunnyIsland reaches a
measuring accuracy of more than 95%. This way, battery overcharge and deep discharge are avoided.
Another advantage of the battery management system is the very gentle charging control. Depending on the battery
type and situation, it selects automatically the optimum charging strategy. This means that overcharging can be reliably
prevented and that the battery can be fully charged regularly. The available charge energy is used optimally at all
times (see technical information "Battery Management" at www.SMA-Solar.com).
Generator Management
The SunnyIsland can synchronize with a generator and connect directly, if necessary. When the stand-alone grid is
connected to the PV array, the voltage and frequency in the stand-alone grid are regulated by the PV array.