Modular multilevel converter as a low inductance machine drive

Many high performance machines are high speed, use permanent magnets, and have a low turns number in conjunction with minimal to no iron. Under these circumstances, the inductance of the machine is very low, i.e. the design of a voltage sourced power electronics drive is challenging from a current regulation/ripple perspective. Traditional approaches to correct this issue include external line reactors between the drive and machine or high switching frequencies. Implemented individually, these techniques are not optimal as external reactors may be bulky and high switching frequencies may cause additional losses in the drive and degrade the mechanical structure of the machine via parasitic coupling. This paper presents the use of a modular multilevel converter (MMC) to drive a low inductance machine. The MMC topology is unique via its ability to combine the operational characteristics of voltage and current source converter topologies to drive zero inductance loads while regulating current.