Multiobjective PWM Strategy With Independent ZSC Suppression, CMV Variation Elimination, and NPV Balance for OEWIM Fed by Dual Three-Level VSI

In an open-end winding (OEW) drive fed by dual three-level voltage source inverters (dual-3L VSI) with a common dc bus, the zero-sequence current (ZSC), the common-mode voltage (CMV) as well as the neutral-point voltage (NPV) are three critical factors needing to be considered simultaneously. ZSC can cause torque ripples and additional losses. CMV can produce shaft current, contributing to bearing failure. NPV adversely affects the quality of the output waveform and voltage safety of the power electronic tubes. However, how to achieve these three objectives simultaneously is still an open question. To solve it, a multi-objective pulse width modulation (MOPWM) strategy is proposed. In this strategy, the vectors with zero CMV amplitude are selected at first to eliminate CMV variation. Following that, some redundant vector pairs consisting of two of these vectors are built according to their spatial positions and their effects on the ZSC and the NPV, which provides the degree to control ZSC or NPV independently. As a result, the conflicts among these objectives are resolved. Moreover, a compensation scheme is proposed to address the negative effect of the dead time on the CMV variation. Finally, the feasibility and the effectiveness of the MOPWM strategy are validated through experiments.