An Optimized Asymmetric Modulation Scheme for Three-Phase Buck Rectifier Without Input Current Distortion at the Sector Boundaries

Space vector pulsewidth modulation (SVPWM) is usually utilized in a three-phase buck rectifier to obtain low total harmonic distortion (THD) and low switching losses. When the conventional SVPWM scheme is applied, the input currents of the three-phase buck rectifier are distorted during the transition from even sector to odd sector, which will deteriorate the harmonics of input currents. In this letter, an asymmetric modulation scheme is proposed to eliminate the distortion of input currents of the three-phase buck rectifier during the transition from even sector to odd sector. The proposed modulation scheme combines two kinds of traditional asymmetric modulations in different sectors. A 1.5 kW experimental prototype of the three-phase buck rectifier with an ac input voltage of 115 V/400 Hz is built for more electric aircraft applications. The experimental results show that the THD of 1.3% can be achieved for the three-phase buck rectifier.