A Novel Unidirectional Three-Phase Multilevel Rectifier Composed of Star-Connected Three Single-Phase Topology Based on Five-Level Flying Capacitor DC–DC Converter

A novel unidirectional three-phase multilevel rectifier composed of star-connected three single-phase topology based on five-level flying capacitor dc–dc converter is proposed, which can be widely applied to many industrial applications, especially for the front-end of multilevel converters for ac adjustable motor drives with open-end winding connection. In addition to not requiring transformers (either line frequency or high frequency), compared to other high-voltage rectifiers, this proposed topology features fewer active switches with lower voltage stress, a high-voltage common dc bus, high input power factor, and low input current harmonics. In this article, a comprehensive analysis to the basic operating principles including the topology configuration, the steady-state modeling, and phase-shifted SPWM modulation is presented. A hybrid control strategy is studied, including the input power factor control, the dc-link voltage balancing control, and the flying capacitor voltage balancing control with balanced and unbalanced loads. Finally, the experimental results are presented to validate the feasibility and correctness of the proposed solution.