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Figure 4.6 MATLAB/SIMULINK model of three level cascaded multilevel inverter.
substantiated and other multilevel converter applications under advancement are pre-
sented [11]. They are categorized by the field of application.
4.1 Energy and power systems
Grid-connected systems, such as flexible ac transmission systems (FACTs), regen-
erative converters, and renewable energy to grid systems are causing main advance-
ments in drives in terms of power quality and efficiency. And since most of these
applications are extended to large power levels, it is not at all an extraordinary fact
that multilevel inverters have drawn the attention as an adaptable solution. Nowadays,
one of the main concerns of renewable energy providers is the integration problem,
because new grid codes relevant to this topic have been conferred in recent years and
are now coming into response. This has prompted research and improvement in mul-
tilevel inverter technology or grid connection of renewable energy sources. In particu-
lar, wind energy conversion provide betterments in terms of efficiency of larger wind
turbines that today can reach up to 5 MW. Therefore, multilevel topologies have been
recommended, mainly NPC back-to-back configurations, as in Fig. 4.7.
Photovoltaic (PV) power-conversion systems are not yet in the multilevel power
rate range. Even though there are some photovoltaic farms spreading up to levels of
