SMA Sunny Island 3324, User Manual

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SMA Technologie AG Glossary
User Manual SI3324/4248-14:FE2406 Page 157
device that prevents power from a solar power system being fed into an external
power grid when the external power generator is not functioning. In the Sunny Boy/
Sunny Mini Central, this function is assumed by the "SMA grid guard Version 2".
Inverters
A device for converting the direct current (DC) from the PV generator into alternating
current (AC), which is used by most normal household devices and especially for
feeding energy into an existing supply grid. Inverters for PV systems usually include
one or more MPP trackers, store operating data and monitor the grid connections of
the PV system (see also MSD).
Inverter mode
See Inverter operation
Inverter operation
Operating mode of a battery inverter where it supplies the stand-alone grid from the
battery energy. In this operating mode, the battery inverter is especially responsible
for the control of frequency and voltage in the stand-alone grid.
Maximum Power Point "MPP"
The working point (current/voltage characteristic curve) of a PV generator where the
maximum power can be drawn. The actual MMP changes constantly depending
(e.g.) on the level of solar irradiation and the ambient temperature.
MPP tracker
Regulation of the power drawn so that a PV generator remains as close as possible
to the MPP. This working point varies with the solar irradiation and the temperature
conditions of the modules. MPP tracking optimizes the extraction of electrical power
and is a feature of inverters and charge controllers.
MSD
See Independent disconnection device
Multi-string inverter
An inverter that combines the advantages of several string inverters (separate MPP
tracking of individual strings) and a central inverter (lower performance specific
costs).
NiCd
Nickel/Cadmium battery, contains Nickel, Cadmium, and potassium hydroxide as
the electrolyte. They require a significantly higher charging voltage, have a lower
level of efficiency and are significantly more expensive than lead acid batteries. Their
robustness, cycle resistance and low-temperature capabilities allow them to be used
in certain special applications.