New optimal pulsewidth modulation for single DC-link dual inverter fed open-end stator winding induction motor drives

The multilevel topologies of dual inverters feeding an open-end stator winding induction motor has been introduced around two decades ago. However, these topologies require common-mode inductor in series with motor windings to suppress zero-sequence or common-mode currents. In medium-voltage high power drives, low device switching frequencies are preferred to improve the overall efficiency of drive system. On the other hand, low device switching frequencies leads to higher total harmonic distortion (THD) of stator currents. Therefore, the objective of our study was to propose a new optimal pulsewidth modulation to eliminate zero-sequence currents and minimize harmonic distortion of stator currents, while operating power semiconductor devices at low device switching frequencies. The main idea is to select switching patterns such that all zero-sequence components are eliminated and then, perform optimization for every steady-state operating point to minimize the THD of stator currents. The proposed modulation has been validated on dual two-level and dual three-level inverters fed 1.5-kW open-end stator winding Induction motor drive.