Noise spectrum shaping in power electronic converters by New RPWM technique

The power electronic converters with fixed switching frequency causes electromagnetic propagation and creates severe harmonics with switching frequency and its multiples in the voltage and current. Presence of strong harmonics in current and in frequency range of human hearing makes the whistling noise that it is unpleasant for humans. Random pulsewidth modulation (RPWM) techniques reduce this harmonics and transforms the frequency spectrum from discrete mode to continuous. In other words, when using RPWM, in voltage spectrum almost all frequencies are excited. Voltage components may match the system resonance frequencies thus, they increase acoustic noise and vibration. In this paper a new RPWM technique is proposed that can create a gap in the noise spectrum at selective frequency to avoid system resonant frequencies being excited. In the following theoretical analysis, computer simulations, are presented.