Random space vector PWM based on the generalized modulator

A classical space-vector pulsewidth modulator (SVPWM) with equal duration of application of zero-state vectors U0and U7was modified. A variable k0(proportional to the time of application of U7) was introduced. By changing k0from 0 to 1, the duration of application of U7can be changed from 0% to 100% of the combined application time for the sum of zero-state vectors. Correlation between modified space-vector and triangle-comparison methods (with added zero sequence) was established. The research showed that many PWM methods can be realized with different value of k0. Based on the investigation, the conception of generalized modulator was put forward. With random change of k0between 0 and 1 in every sampling interval, the RPWM of random zero-vector distribution can be realized by generalized modulator. Random PWM technology is a direct and effective way to alleviate acoustic noise in adjustable-speed system. The experiment results verified the effectiveness and practicability of the random PWM.