Harmonic Suppression Capability Enhanced for 12-Pulse Rectifiers Using a Single-Switch Step-Quadrupling Circuit

To effectively suppress the harmonics of a 12-pulse rectifier without increasing the complexity of the phase-shifting transformer, this paper proposes a single-switch step quadrupling circuit (SSSQC) for constructing a low-harmonic multi-pulse rectifier. The proposed rectifier topology consists of a conventional 12-pulse rectifier and an SSSQC, where the SSSQC is installed on the DC side of the rectifier. The MOSFET Q1 in the SSSQC is triggered according to the voltage relationship between the multi-tapped interphase reactor (MT-IPR) winding and the load, enabling the rectifier to operate in five distinct operating modes. By regulating the coupling relationship between the AC and DC sides, the number of steps in the input current is increased from 12 to 48, allowing the input current to more closely approximate a sinusoidal waveform. Consequently, the total harmonic distortion (THD) of the input current is reduced from 12.2% to 2.2%, achieving effective mitigation of input current harmonics. The power rating of the proposed SSSQC is only 2.44% of the output power, and the scheme employs only a single MOSFET Q₁, featuring a simple structure, easy implementation, and low cost. Finally, a 1.8 kW laboratory prototype is developed to verify the validity of the theoretical analysis.