Three-phase six-pulse buck rectifier with high quality input waveforms

The design and analysis of a three-phase, six-pulse buck rectifier is presented. The PWM modulation technique is analysed using the commuting function. Such analysis represents the main design tool for the commutation sequence, since it provides information about the harmonic behaviour of the rectifier signals with respect to the parameters involved in the modulation. The carrier signal is selected after a spectral analysis has been performed, to minimise the harmonic distortion content, thus obtaining high quality input currents. Likewise, as an additional and helpful tool for the designer, a digital circuit was developed to generate and store the commuting function, which is then applied to the rectifier. Some tests were carried out on a prototype. The results which focus on the power factor and the total harmonic distortion are presented.