Random PWM scheme for 3-level inverter using offset time randomization

This paper proposes a space vector based Random Pulse Width Modulation (RPWM) scheme for a 3-level inverter. A constant switching frequency technique is employed in this scheme. Randomization is achieved by placing the effective vector randomly in the constant switching time period. The random position of effective vector is calculated from the instantaneous amplitude of the 3-phase reference signals. The method requires no sector identification. No external circuitry is required for generating the switching vectors. The proposed scheme can be implemented for any 3-level inverter topology. In the present work, the scheme is implemented and tested for a dual inverter fed 3-level open-end winding induction motor drive using DSP platform, TMS 320LF2407A and experimental results are presented.