Large virtual voltage vectors for direct controllers in six-phase electric drives

Abstract

The appearance of virtual voltage vectors (VVs) has simultaneously provided two attractive features for multiphase drives: a simple and effective regulation of the x-y currents and a natural fault tolerance that avoids any control reconfiguration after an open-phase fault occurrence. VVs in six-phase drives were initially constructed using large and medium-large voltage vectors, and all subsequent works adopted this procedure without contemplating other alternatives. The use of medium-large vectors limits however the utilization of the dc-link voltage and brings undesired switching harmonics. This work goes back to the initial definition of the VVs and suggests using exclusively large (adjacent) voltage vectors to create the newly proposed large virtual voltage vectors (LVVs). Experimental results confirm that LVVs provide better current quality, lower switching frequency and better dc-link voltage utilization than standard VVs.