A new random PWM(SRP-PWM) technique for decreasing acoustic noise radiated from V/F controlled motor drives

Comparison of Different Control Strategies of Multilevel Inverters Used to Fed a Dual Star Induction Machine

“…The method is based on a random selection of the carrier frequency for each carrier period [13][14][15][16][17][18]. In this technique the randomization of frequency of carrier wave is by taking some times the carrier wave and the other times the inverse of carrier wave.…”

“…So, for do this we work with PRBS (the random bits generator, Figure 4) which it generates random bites even 0 or 1, we take the result of PRBS and multiple with the carrier wave and the inverse of PRBS multiple with the inverse of carrier wave and add the both results like it's been shown in Figure 4. where, if the result of PRBS is one the inverse is 0 so the carrier wave is the same as classic PWM, but if PRBS generate 0 the carrier wave become the inverse of the carrier wave [13][14][15][16][17] in this way we make a carrier signal ( Figure 5) with random frequency which sometimes is bigger than the frequency of the same carrier wave and that's increase the quality of the fed wave because the THD is lower when the carrier frequency is higher.…”