Unity Power Factor Control for Three-Phase Three-Level Rectifiers Without Current Sensors

Three-level rectifiers with reduced number of switches (such as the Vienna rectifier) to improve the input power quality of rectifier systems have been receiving wide interest in the past years. In this paper, a new carrier-based pulsewidth-modulation control algorithm is proposed for such converters to eliminate the low-frequency harmonics in the line current while achieving unity power factor at the rectifier input terminals. The operating constraints of the Vienna rectifier with the carrier-based modulation strategy are examined carefully, and the proposed control algorithm ensures that appropriate voltage/current directional constraints are met. A promising cost-reduction opportunity can be seen with the elimination of input current sensing to operate the Vienna rectifier. The control algorithm is verified via Saber simulation and experimental results.