An improved predictive control for three-phase PWM AC/DC converter with low sampling frequency

In this paper an improved predictive current-controlled three-phase PWM AC/DC converter is described. An analysis is given to explain the phase shift caused by the predictive current control for PWM AC/DC converter which, at low sampling frequency, results in a failure of the converter for power factor control. A compensation circuit is then applied to correct the phase shift to ensure the predictive control with high power factor. The space vector PWM strategy is employed to obtain small current and DC voltage ripples as well as high performance. Moreover, an investigation result shows the possibility to apply small filter capacitance in DC link of the designed PWM converter. The simulation results verify a satisfactory performance of the system with nearly unity power factor both in rectifying and regenerating operations at low sampling frequency, small current ripple and fast dynamic responses in the condition of comparatively small DC link capacitance