2.
Isolated DC-DC converters and some non-
isolated DC-DC converters can provide inherent
fault current blocking (or limiting) capability.2.2 Modular multilevel converter
Modularity critical design consideration for DC
voltage conversion MVDC networks, particularly
when addressing the voltage scaling limitations of
individual converters. Its key advantages
include redundancy, low switching losses and high
voltage output capability.3 DC-DC voltage conversion
DC-DC converters are generally categorized into
two main groups: isolated and non-isolated [41]. These limitations arise from
the lack commercially available high voltage
semiconductors; most semiconductor switches are
typically rated below 6. Prominent
isolated topologies are buck-boost and modular
multilevel. Because
of these characteristics, there growing interest
in leveraging MMCs connect BESS [39] and PV
plants [40] power grids. Isolated DC-DC converters incorporate
a DC-AC-DC conversion sequence, typically
involving two stages AC-DC conversion. Non-
isolated DC-DC converters not require power
transformer and use fewer semiconductors, and
so are more efficient, smaller and cheaper than
their isolated counterparts, but cannot operate at
the voltage ratios isolated converters.34
MVDC technologies and operational considerations
Figure 4-2 High power voltage source converter families
4.
Isolated converters offer galvanic isolation via an
intermediary transformer, protecting the low
voltage side the converter from the high voltage
side, with prominent topologies such dual active
bridge (DAB), DAB-resonant and modular multilevel
DAB.
The basic design MMC involves switching
submodules that cascade together the
AC side the converter.
.
4. This
must kept mind when designing the MVDC
network protection. Each submodule is
equipped with floating capacitor the DC
side, enabling the integration sources and/
or loads, illustrated Figure 4-3. The MMC, introduced
in 2001, seen one the most suitable power
electronic converter topologies interface HVDC/
MVDC grids and grids.5 kV
