A new nine-level boost PWM rectifier based on stacked multilevel concepts

In this paper a new AC/DC unidirectional switching cell with nine voltage levels is proposed. It is called Stacked-Flying-Capacitors-Coupled-Inductors (SFC²I) and can be connected between an AC current source and a DC voltage source. The novelty of 9L-SFC²I topology is based on two cascaded stages that work at different currents, different voltage and different switching frequency. The first stage contains two diodes that operate at high-current, high-voltage and low-frequency. The second stage works at low-current, low-voltage and high-frequency. It combines the advantages of two stacked multilevel concepts, named Stacked-Flying-Capacitors (SFC) and Stacked-Coupled-Inductors (SCI). The SFC principle reduces the energy stored in flying-capacitors, while the SCI concept naturally sets to zero any difference between the winding currents of the coupled-inductors after each cycle. The operation principle of the 9L-SFC²I cell is verified both for single- and for three-phase unity-power-factor PWM rectifiers.