Three-level PN cell for multilevel converters

Multilevel converters rely on plurality of DC capacitors switched in specific patterns to obtain the necessary output voltage level. Modular multilevel converter, flying capacitor converter (FLC) and neutral point clamped (NPC) converters require complex control to balance the capacitors' voltages. Cascaded H-bridge (CHB) converters require plurality of isolated DC sources to energise the capacitors. This study presents a three-level PN cell that modulates the common-mode voltage between the output and input port while simultaneously mirroring the input DC voltage on the output port. Cell's capacitor voltage is naturally balanced and a three-phase multilevel converter requires only one DC power source. The output voltage of a multilevel converter can be higher than the input DC voltage. As a consequence, a single low-voltage DC power source can directly interface a three-phase MV grid.