Hybrid PWMs for shaft voltage reduction in a dual inverter fed induction motor drive

Dual two-level inverter employing an open-end winding induction motor stator windings works as a three-level inverter. This paper presents investigations on the common mode voltage in the dual-inverter scheme that identified to be different from the zero-sequence voltage. The relation between the common mode voltage in the dual-inverter scheme and the common mode voltages of the individual two-level inverters is also established in this paper. The degree of freedom of operating the individual inverters independently is exploited in this paper and hybrid PWMs are proposed for the dual-inverter scheme that significantly reduce the magnitude as well as the number of levels of the shaft voltage in the induction motor drive when compared to the use of sinusoidal PWM method. Suitable experiments are performed on a three-phase induction motor drive, driven from the hybrid PWM controlled dual-inverter in order to validate the proposed PWM methods.