PWM inverter switching strategy for a dual two-level inverter fed open-end winding induction motor drive with a switched neutral

Abstract

A dual two-level inverter fed open-end winding induction motor drive is proposed in this paper. A total of 64 voltage space phasor combinations are possible in this scheme since each inverter produces eight voltage space phasors. The scheme produces voltage space phasor locations similar to that of a three-level inverter except that in a three-level inverter the series-connected DC link capacitors carry the load current, which results in undesirable fluctuating voltage space phasors. Also, a three-level inverter requires a bulky DC link capacitor. In the proposed scheme the DC link capacitor carries only the ripple current and hence the voltage space phasor fluctuations are absent. A PWM switching strategy aimed at suppressing the zero sequence currents is proposed, using auxiliary switch-assisted neutral generation.