Glossary - SMA SMC 5000A Installation Manual

SMA
Technologie AG

Glossary

14 Glossary
AC
Abbreviation for "Alternating Current"
Central inverter
An inverter concept in which all PV modules are connected to each other (in series and/
or parallel) and which uses a single inverter for feeding energy into the mains supply
network.
DC
Abbreviation for "Direct Current"
Derating
English for "reduction": a controlled reduction in performance, usually dependent on
component temperatures. Compared with the normal process of completely shutting
down the device, the effect on the external power network is smaller with derating.
Grid impedance
The grid impedance is a characteristic grid specification, which is determined by the
grid's infrastructure, as well as by the number of power suppliers and power consumers.
If supply to the grid section drops out due to a grid shutdown on the part of the adjacent
supplier (medium voltage transformer), the grid impedance changes abruptly. In order
to detect this occurrence, and to prevent an unwanted stand-alone grid, SMA grid gu-
ard measures the grid impedance and disconnects the inverter from the grid in the event
of a jump in impedance.
Inverter
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 fee-
ding energy into an existing mains supply network. Inverters for PV-systems usually con-
tain one or more MPP-trackers.
Mains coupled system
A PV system that is connected to the mains supply grid of an external energy supplier.
Maximum Power Point "MPP"
The operational point (current / voltage) of the PV generator at which the highest pos-
sible performance under the prevailing conditions is achieved. The actual MPP changes
constantly depending (e.g.) on the level of solar irradiation and the cell temperature.
Installation Guide SMC50A_60A-11:SE3706 Page 99