Advantages: All of the phases share

Advantages:
All of the phases share a common dc bus, which minimizes the capacitance requirements of
the converter. For this reason, a back-to-back topology is not only possible but also practical
for uses such as a high-voltage back-to-back inter-connection or an adjustable speed drive.
The capacitors can be pre-charged as a group.
Efficiency is high for fundamental frequency switching.
Disadvantages:
Real power flow is difficult for a single inverter because the intermediate dc levels will tend
to overcharge or discharge without precise monitoring and control.
The numberof clamping diodes required is quadratically related to the number of levels,
which can be cumber some for units with a high number of levels.