Voltage-phase shifting effect of three-phase harmonic canceling reactors and their applications to three-level diode rectifiers

For replacing a conventional transformer-coupled system, a novel double rectifier system with 24-step input voltages is proposed for mid-power applications. The system consists of double three-level voltage-type diode rectifiers coupled with three harmonic canceling reactors with a total power capacity of 13.4-18.2% of the DC output power. Additional switches of the unit rectifiers act as forced commutation circuits and the reactors absorb lower harmonics. The proposed system has the advantages over conventional transformer coupled systems of: economical design; small size; light weight; high-quality input currents; and highly reliable operation