Sunny Island Catalgoue - Sinetech

Multi-String Inverters
The Multi-String allows the connection
and the MPP operation of several
strings via DC/DC converters on one
common bridge and provides a compact
and price-effective solution while
still offering the advantages of the
string technology. PV systems consisting
of strings with different geographical
orientation (south, west, east), and
the resulting different time period during
which the power is produced, can
be operated with optimal efficiency.
Multi-String inverters are used in PV
systems in the medium power range
between 3 and 10 kW.
a complex cabling on the AC side,
due to the fact that each module of
the system must be connected to the
230 V grid. With respect to the greatly
increased number of required module
integrated inverters, the complexity of
the circuit increases drastically. This
concept is normally only used in PV
systems with less power, from 50 up
to 400 W.
These three types of inverters are available
on the market. The choice of the
most appropriate inverter depends on
the corresponding application.
Module-integrated Inverters
One inverter is used for each module,
as shown in Fig. 2c. This topology
optimizes the adaptability of
the inverter to the PV characteristics,
since each module has its own MPP
tracker. The efficiency of module integrated
inverters cannot be compared
with the efficiency of string-inverters.
Module integrated inverters require
a) b) c)
Fig. 2: schematic diagram of a PV plant connected with three different topologies:
a) central inverter b) string inverter c) module-integrated inverter
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