SMA Sunny Island 2012 Technical Description page 208

SMA Solar Technology AG
Glossary
Multicluster System
Parallel connection of several clusters on the AC output side in a stand-alone grid or backup system.
The master devices of the individual clusters must be connected by communication cables, and
configured in such a manner that one cluster leads the entire system (see main cluster) and the
master devices of all other clusters (see sub-cluster) communicate with the master of the main cluster.
Multi-string inverter
An inverter which to a great extent combines the advantages of several string inverters (separate
MPP tracking of individual strings) and a central inverter (low performance-specific costs).
NiCd
Nickel/cadmium battery, contains nickel, cadmium, and potassium hydroxide as the electrolyte.
These require a significantly higher charging voltage, have a lower level of efficiency and are
significantly more expensive than lead acid batteries. However, their robustness, cycle resistance
and low-temperature capabilities mean that they are used in certain special applications.
NLM
Abbreviation for "Netzleitungsmodem" (Powerline modem): communication between SMA inverters
and monitoring devices is possible via a cable, a radio link, or a Powerline modem. Powerline
modems use a carrier frequency of approx. 132 kHz modulated onto the AC cables, and data is
transferred using FSK (Frequency Shift Keying) of this carrier signal. Details on the Powerline modem
can be found in the technical description of the SMA-NLM among other places.
Nominal Charge Throughput
The charging throughput is the cumulative total discharge current over time, measured in ampere
hours (Ah). These meters are not automatically reset after charging. The nominal charging
throughput is the charging throughput with regard to the nominal capacity of the batteries.
Overload Capability
The overload capability of an inverter describes its ability to supply short-term (seconds or minutes)
excessive loads that can be significantly higher than the nominal capacity of battery inverters. The
overload capability is important to allow startup of electrical machines which have a nominal power
output close to the nominal power output of the stand-alone grid inverter, since these machines
typically require six times the nominal current when starting.
Parallel connection
Parallel connection of batteries (all positive poles together and all negative poles together)
increases the capacity of the battery bank while keeping the voltage constant. For example, two
24V/100Ah batteries connected in parallel still have a voltage of 24 V, but have a capacity of 100
Ah + 100 Ah = 200 Ah.
Photovoltaics
See "PV"
208 SI2012_2224-TEN082311 Technical Description