Direct Control Strategy for a Three Phase Eight-Level Flying-Capacitor Inverter
Résumé
Flying-capacitor converters is a multilevel topology which provide several advantages
over classic two level converters. They reduce a dv/dt phenomena and offer a better harmonic
content. On the other, thanks to the series connection of commutation cells, they provide a
means of increasing power and voltage. Furthermore, for certain failures, their structure can be
reconfigured in order to work in degraded mode. However, all these advantages come at the price
of a more complex control since it is necessary to maintain the flying capacitors voltages at their
target operating levels. To overcome this problem and motivated by an industrial application in
collaboration with GS Maintenance company, a direct control strategy is proposed for a three-
phase eight-level flying capacitor inverter. It is showed that the control strategy is simpler than
other control algorithms proposed in the literature, like for example Pulse Width Modulation
(PWM) control, and leads less expensive hardware implementations. Moreover its stability is
proved by means of Lyapunov theory. This approach is compared to the conventional PWM
control to show its good performances during disturbances through simulation results.