A performance comparison of PWM techniques for five-leg VSIs supplying two-motor drives

Component minimized multi-machine drives have recently become an area of much research interest. One such drive comprises two three-phase induction motors supplied by a five-leg voltage source inverter (VSI). With only five legs available to supply two three-phase motors one inverter leg is connected to both motors and the drive is controlled in such a way that both machines can operate independently. A number of PWM methods have recently been developed for such a drive system. This paper compares, by simulation, four of the available techniques and shows that the PWM method termed as dasiadouble zero-sequence injectionpsila is by far the best. It is the only method which enables an arbitrary distribution of the available DC link voltage between the two machines, while still being able to operate with equal and constant switching frequency in all five inverter legs. Experimental results, which illustrate operation with double zero-sequence injection PWM and thus verify the theoretical findings, are provided.