This paper studies an energy storage system based on a three-level DC-DC converter and a gridconnected
neutral-point-clamped inverter. The main advantages of this multilevel power conversion
system are highlighted and the neutral-point voltage oscillations are analyzed. A modulation algorithm
for the DC-DC converter which includes the neutral-point voltage balance control is used to improve
the voltage balancing capabilities of the inverter. Some figures are presented to show the extended
operating areas without neutral-point voltage oscillations thanks to the contribution of the DC-DC
converter to the voltage balance. Finally, some guidelines to size the DC-link capacitors are given for
a practical application.Peer ReviewedPostprint (published version