Abstract

Dual-inverter fed open-end winding (OeW) motor drives offers many advantages over the single multi-level inverter fed motor drives counterpart. However development of modulation method for the dual-inverter fed drives is formidable due to high number of the available switching states. This paper proposes four PWM schemes for the dual-inverter fed OeW 3-phase motor drives. The PWM schemes are developed by dividing the voltage references in a certain way and modulating them in the same or different PWM technique. Simulation results show that the Mixed Switching Frequency (MSF) PWM provides the best output voltage quality among the PWM schemes especially for M > 0.575. At maximum modulation index (M =1.15), THD of the output voltage is improved from 52.88 %, 52.76 %, 32.74% for ERS, URSI and URS2 PWM scheme respectively to 27.45% for the MSF PWM. Further investigation also reveals that the performance of PWM scheme relates with the utilized switching states. The ERS PWM utilizes only 8 switching states while the URS and MSF PWM utilizes 38 switching states among the 64 available states. The MSF PWM is able to select the most effective switching states hence provide a better waveform multi-level outputs compared with the URS PWM methods.

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