Comparative evaluation of modulation methods of a three-phase buck + boost PWM rectifier. Part I: Theoretical analysis

Different switching state sequences of a three-phase three-switch buck-type unity power factor PWM rectifier with integrated DC/DC boost output stage are presented. They are analysed concerning switching losses and ripple components at the input (filter capacitor voltage ripple) and at the output (DC link current inductor ripple). For a fair comparison, pulse frequencies of different modulation methods are adopted in order to achieve the same switching losses. The rms value and envelopes and time behaviour of the ripple components are analysed analytically and by simulation, and one advantageous modulation method is determined. The paper provides the basis for a subsequent experimental verification, which is performed in part II.