Random SVPWM technique for three-level vector control inverters

Aiming at the optimizing pulse width modulation(PWM) control in three-level vector control inverter,a random space vector PWM(SVPWM) method with fixed switching and sampling frequency is proposed.In this method,all vectors action time was randomly assigned between the ascent and descent stage of each triangle carrier on the basis of the unchanging voltage-second balance law,and the random effect does not rely on the zero vectors.To insure better random effect of the SVPWM,a design for maximal-length shift register sequences(M-sequences) was proposed.Simulation and experiment results show the proposed scheme leads to a well-distributed spectrum of the line-to-line voltage and phase current,and smaller harmonic amplitude at the integral multiple of the switching frequency compared with the conventional SVPWM.