The Effects of RPWM on the Conducted Electromagnetic Emissions in Bidirectional Three-Phase Unity Power Factor Boost-Buck Converter

A three-phase PWM unity power factor boost-buck converter generates harmonics at switching frequency and its multiples. This concentrated power spectrum density may produce ElectroMagnetic Interference (EMI) problems and switching losses. In this paper, the Random Pulse Width Modulated (RPWM) technique is employed in order to distribute the power spectrum density on a larger range of frequencies without affecting the fundamental frequency component. Therefore, the amplitudes of these harmonics decrease and both switching losses and radiated EMI are reduced. The RPWM generator developed by using Matlab/Simulink software is detailed and a spectral analysis of the input current is carried out for the two modulation techniques (PWM and RPWM).