Current-fed multilevel converters: An overview of circuit topologies and modulation techniques

Multilevel converters (MLC) have emerged as standard power electronic converters in high power as well as quality demanding applications. Voltage-fed MLCs have been widely researched whereas the current-fed (CF) MLCs are the recent topic of research. CF-MLC offer several advantages in terms of high power capability, transformer-less operation, short circuit protection and excellent quality of output current waveform. Compared to voltage-fed MLCs, the operation of CF-MLCs need to satisfy additional switching constraints which needs to be included in modulation signals. The goal of this paper is (1) to present review of circuit topologies, methods for incorporating the switching constraints, modulation schemes and applications of CF-MLCs and, (2) to propose an emerging low device switching frequency modulation technique known as synchronous optimal pulsewidth modulation for CF-MLCs.