IGBT Modules - Technologies, Driver and Application (Second Edition) - page 419

11.6.3Solar power inverter
To reduce the dependence on fossil fuels, since the 1990s solar energy has become
much more popular. In the last few years - due to the rapid rise in energy costs for oil
and gas - this has become more and more of interest to the public. The application
range of inverters for solar applications now stretches from a few 100W up to several
100kW and more. Due to the different possible combinations of solar panels and solar
inverters amultitude of variations are possible as shown i
Thismay include,
for example, the panels connected in series (this is referred to as a string) and then
several strings in parallel. The inverter is fedwith input voltages from 100V up to (rarely)
several kilovolts. The inverter converts the DC voltage into a suitable single- or three-
phase ACmains voltage. For input voltages of only a few volts (such as resulting from
the arrangement of
) the inverter includes a boost converter input stage
which raises theDC voltage to a level that is necessary to a subsequent supply into the
Fig. 11.43
Exampleof combinations of solar panels and solar inverters
The topologies used for solar inverters vary mainly by whether electrical isolation is
made with a transformer or not. Furthermore, the selected switching frequency will
decide whether the power semiconductors used are MOSFETs or IGBTs (with
freewheeling diodes). The higher the total system power, the more likely is the trend to
use IGBTs or IGBTsmodules.
Two aspects are outstanding regarding the requirements for solar inverters: High
efficiency and low distortion of the provided output voltage. Because of these demands,
three-level topologies are becoming increasingly popular. Also SiC diodes have already
beenestablished in this application segment.
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