Random modulation schemes for industrial drives

Random Pulse Position Pulse Width Modulation (RPPPWM) scheme can achieve the distributed harmonic spectrum of both voltage and current. This results in reduction of acoustic noise and mechanical vibrations. The gate signals are generated by comparing sine wave and pseudorandom bits (PRBS). The PRBS random bit generator is implemented using a shift register. In this paper, an induction motor driven with a RPPPWM controlled inverter is designed and simulated. The simulation results indicate uniform distribution of harmonic spectrum of inverter output and thus the acoustic noise and mechanical vibrations are reduced.