Two-Leg Neutral-Point Diode-Clamped Active Front-End Rectifier

Active front-end boost rectifiers can replace the uncontrolled diode bridge rectifiers for ac-dc conversion offering high power quality with near unity power factor. The four-switch, B4, topology is gaining interest, either as an inverter or a rectifier, where each switch should withstand the full dc-link voltage. Higher voltage-rated power semiconductor devices not only imply slower response with lower overall efficiency but also higher cost and size. Thus, multilevel inverters become a viable solution. This article investigates a two-leg neutral-point diode-clamped B8 rectifier allowing the series connection of fast, efficient, and low voltage-rating switches. The proposed rectifier has a better performance and efficiency than the B4 rectifier. Only two inductors instead of three are required. Model predictive current control (MPCC) is developed for accurate current tracking. A model of the proposed rectifier is detailed for the implementation of MPCC. The concept is validated by simulation and experimentation.