An open-end winding approach to the design of multi-level multi-motor drives

An Open-end Winding approach to the design of multi-motor drives exploiting multi-level inverters is presented in this paper. A key feature of the proposed approach is that a single multi-level inverter is tasked to provide the entire active power required by the system, while a two-level inverter acts as a power filter, providing a zero average active power. Moreover, a staircase voltage modulation technique is adopted on the multi-level inverter in order to minimize the switching losses, while the two-level inverter is PWM operated to accurately shape the motor currents. The proposed solution produces a much lower stator current distortion if compared to a conventional MLI switching at the fundamental frequency, while it requires less power switches and generates lower power losses than a PWM multi-level inverter featuring the same THD. Experimental results obtained on Multiple Motor Single Converter and Multiple Motor Multiple Converter systems are provided in order to confirm the consistence of the proposed approach in terms of efficiency maximization and motor voltage THD minimization.