Minimization of the DC current ripple of a three-phase buck-boost PWM unity power factor rectifier

The modulation of a novel three-phase three-switch buck-type unity power factor rectifier with integrated DC/DC boost converter output stage is optimized concerning the ripple amplitude of the buck-boost inductor current. This is achieved by coordination of the switching operation of the buck input stage and of the boost output stage. A comparative evaluation of different modulation schemes does identify a modulation scheme which simultaneously does provide minimum DC current ripple and minimum input filter capacitor voltage ripple at minimum switching losses and/or maximum pulse frequency. All theoretical considerations are for operation in a wide input voltage range and are verified by simulations and by measurements on a DSP-controlled 5 k W prototype of the system