13 Multicluster Technology Terms
SMA Solar Technology AG
Operating manual
MC-BOX-6-3-BE-en-30
34
13 Multicluster Technology Terms
Stand-alone grid
A stand-alone grid is a utility grid which is independent of the public energy supply. A stand-alone
grid with Sunny Island is designed as a single-phase or three-phase AC grid which integrates
various kinds of power generators (e.g., PV systems, small wind turbine systems and diesel
generators).
Batteries for energy storage are also an integral part of stand-alone grids. The Sunny Island battery
inverter forms a stand-alone grid and maintains a stable energy supply by regulating all processes.
Cluster
A cluster is made up of three Sunny Island inverters and one battery. One Sunny Island inverter per
line conductor, i.e., three Sunny Island inverters in total, are connected to form a three-phase stand-
alone grid. Within the cluster, one Sunny Island is the master, while the other two are slaves.
Multicluster system
A multicluster system is made up of several clusters connected in parallel. The power of the
multicluster system increases with the number of clusters. The individual clusters must be connected
to a Multicluster-Box. The size of the Multicluster-Box is determined when the system is designed
depending on the power requirement.
Multicluster-Box
The Multicluster-Box is the AC main distributor in a multicluster system. The Multicluster-Box connects
the Sunny Island clusters with the loads and the power generators within a stand-alone grid.
Master
The master is the control and communication center in a cluster. It carries out the following tasks:
• Switching slaves on and off
• Controlling and monitoring the slaves, e.g., regulating frequency and voltage
• Controlling battery charge and discharge
• Monitoring battery capacity and state of charge
• Storing cluster and battery data on SD memory card
• Requesting diesel generator
• Exchanging data with the masters of other clusters
• Updating both slaves after firmware updates
• Displaying system values and system states
• Central capture of user entries
Slave
A slave is a functional unit subordinated to the master. A slave receives its configuration settings,
current firmware updates, and start/stop commands from the master. It transmits its operating data
to the master and executes commands issued by the master.
