Multicluster Operation
SMA Solar Technology AG
130
SI5048-TEN093630
Technical Description
16.4 Generator Operation
The main master's generator request comprises its own request (based on SOC, time, etc.) and
possible requests from one or more extension clusters. The generator remains in a requested state as
long as a request is present.
16.5 Behavior with Different Charge States
In multicluster systems, each cluster has its own battery bank. To prevent the charge states of the
various battery banks from diverging over time, a function for equalization of the charge states is
integrated into the Sunny Island devices. This ensures that instead of the power always being divided
equally among all clusters, the cluster with the highest charge state delivers the highest output, or
charges its battery with the lowest amount of power.
The differences in outputs depend on the differences in charge states, and amount to 1 % of the
nominal power per 1 % difference in charge status. Thus, when initial charge states differ, equalization
of the charge states over the course of time is ensured. If all batteries in the various clusters have the
same capacity, the charge states should always be within a few percent of each other. Only if a fault
occurs, or upon deliberate deactivation of individual clusters, can a greater imbalance arise, but even
so, such an imbalance should also be equalized after one day at most.
Generator Request
The established generator request at the extension clusters is transferred to the main master
via a communication connection.
Nominal capacity of the battery banks
Ideally, the various battery banks should all have the same nominal capacity.
In the event of differences of up to 30 %, the equalization function guarantees a similar
average charge state. However, the smallest battery is then cycled more intensively. The
nominal capacity and overload capability are no longer equal to the value of an individual
device multiplied by the number of devices, but are 10 % - 20 % lower for the cluster with
the smaller battery.
Summary of Contents for SI 5048
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