Harmonic Reduction for 12-Pulse Rectifier Using Two Auxiliary Single-Phase Full-Wave Rectifiers

A simple and robust harmonics reduction scheme for 12-pulse diode rectifier using two auxiliary single-phase full-wave rectifiers (ASFRs) is proposed in this letter. The two ASFRs are installed at the dc side of the rectifier. One ASFR is connected in series with the load to directly modulate the output current of double star rectifiers (DSRs), whereas another ASFR is connected in parallel with the load to indirectly shape the output current of DSRs. The coadjutant modulation of the two ASFRs increases the output current states of DSRs first, thereby increasing the number of steps in the input line currents. This modification extends the conventional 12-step input line current to a 36-step input line current. The proposed rectifier draws near sinusoidal input line currents with the absence of 11th, 13th, 23rd, and 25th harmonics. Since only two ASFRs are sufficient, the proposed rectifier is completely passive and has the least number of component count, making it robust and simple to implement. Analytical results are experimentally verified on 1.8-kW experimental rectifiers.