Contents I. Introduction
In recent years, medium voltage drives have been rapidly developed mainly because of the introduction of series multilevel converters. In these converters, the voltage to be switched is shared among several semiconductors, which allows these converters to reach higher dc bus voltages. Many different topologies can be used, but they generally consist of combinations of five main types which have been successively introduced: polygonal and cascaded, neutral point clamped, flying capacitor, Sparc, and M2C [1]–[11]. Multilevel conversion is not a priori limited to voltage source inverter (VSI), but three-phase drives are a huge market, and a lot of effort has been made to optimize the operation of multilevel three-phase VSI. In particular, modulation techniques have been thoroughly investigated, resulting to different options in using the zero sequence component of the reference as a degree of freedom [12]–[21]. When it comes to comparing the performance of these different strategies, the approach presented in [22] is efficient.
