Power factor control of a three-phase boost rectifier with specific power factor under asymmetrical conditions

A new current controller structure for the three-phase boost rectifier, using actual phase currents achieving both controllable input power factor and constant DC voltage under asymmetrical source voltages and/or unequal line impedances, is presented in this paper. All the control variables in the new scheme are AC signals instead of the DC signals used in the industry standard synchronous reference frame controllers, eliminating the synchronous reference transformations of the currents, voltages and the hardware (phase lock loop) or software required for voltage phase angle measurement. Under asymmetrical source voltages, a generalized discontinuous PWM method is also developed which can also reduce the device switching loss of the rectifier. An attraction of this controller strategy lies in the ability to transparently achieve leading, lagging and unity power factor operation with regulated DC voltage. With a digital signal processor (DSP), the proposed control algorithm has been experimentally implemented; the experimental results demonstrate their significant effectiveness.