Harmonic reduction of CO/sub 2/ welding machine using single-switch, three phase boost converter with sixth order harmonic injected PWM

In this paper, sixth order harmonic injected PWM for improving input current distortion of single switch three phase boost converter is presented. A periodic sixth order harmonic voltage is injected in the control circuit to vary the duty ratio of the converter switch within one switching cycle. As a result, the input phase currents are forced to track the input voltage and almost unity power factor is obtained. Experimental results are verified by a converter operating at 400 V/6 KW with three phase 140 V-220 V input and by a CO/sub 2/ arc welding machine which was nonlinear load with 3/spl phi/ 220 V input.