Discontinuous decoupled SVPWM schemes for a four-level open-end winding induction motor drive with waveform symmetries

Abstract

A four-level open-end winding induction motor drive (OEWIMD) is realised by feeding the open stator windings of a three-phase induction motor from either end with two-level voltage source inverters (VSIs). These VSIs are operated with unequal DC-link voltages, which are in the ratio of 2:1. This circuit configuration has the disadvantage of overcharging the DC link capacitor of the inverter operated with the lower input voltage. Decoupled space vector pulse-width modulation (DSVPWM) schemes, which were suggested in the previous literature to circumvent this problem, result in higher switching power loss in the dual-inverter topology. It is known that the discontinuous pulse-width modulation (PWM) schemes reduce the switching power loss. However, lack of structural symmetry of the power circuit renders it unwieldy to devise these PWM schemes. This study explores the applicability of discontinuous decoupled SVPWM (DDPWM) techniques for the four-level OEWIMD, without compromising on the waveform symmetries. With the aid of an improvised loss model, it is shown that these PWM schemes achieve the reduction of the overall loss of the four-level OEWIMD compared to the DSVPWM schemes. It has also been observed that one of the proposed DDPWM schemes result in reduced dv⁄dt in the motor phase voltages