In the three-phase PWM converter, the source phase currents have been independently controlled. But, in the unsymmetrical three phase voltage system, the source currents are distorted by the independent phase control method. If the extension pq method is applied to the three phase PWM converter, the source current will not be distorted. In this paper, the authors propose the application of the extension pq theory to the PWM converter and clarify the effectiveness by simulation.