Load Shedding In A Multicluster System; Generator Operation; Behavior With Different States Of Charge - SMA SUNNY ISLAND 4548-US Operating Manual

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16.3.3 Load Shedding in a Multicluster System

The load-shedding contactor in the Multicluster Box is controlled depending on the state of charge of
the batteries.
Significance of the SOC thresholds:
When the state of charge of a battery reaches the lower SOC threshold, the load contactor is opened.
The state of charge of the battery of the main cluster and the states of charge of the batteries of the
extension clusters are evaluated. The load contactor disconnects the loads from the stand-alone grid.
When the state of charge of all batteries reaches the upper SOC threshold during recharging, the
load contactor closes. The load-shedding contactor connects the loads to the stand-alone grid.
The load shedding of the Multicluster Box only reacts to the SOC value of the main cluster.
1. Select the parameter "242.01 Lod1SocTm1Str" and set it to the lower SOC threshold.
2. Select the parameter "242.02 Lod1SocTm1Stp" and set it to the upper SOC threshold. The
upper SOC threshold must be at least 10 percentage points above the lower SOC threshold.
3. Set the parameter "242.05 Lod1Tm1Str" and the parameter "242.06 Lod1Tm2Str" each to the
same value, e.g. to 000000. This will switch the time-dependent load shedding off.

16.4 Generator Operation

The generator request of the main master 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.
Generator request
The determined generator request at the extension clusters is transferred to the main master via
a communication connection.

16.5 Behavior with Different States of Charge

In Multicluster systems, each cluster has its own battery-storage system. To prevent the states of charge
of the various battery storage systems from diverging over time, a function for equalization of the
states of charge is integrated into the Sunny Island inverters. This distributes the power to all clusters,
however, it is not always distributed identically. Instead, the cluster with the highest state of charge
discharges the most power or charges the battery with the lowest power.
The differences in power depend on the difference in the state of charge and total 1% of the nominal
power for each 1% of difference in the state of charge. Thus, when initial charge states differ,
equalization of the states of charge 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 the latest.
Operating Manual
16 Multicluster Operation
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