A four-level π-type converter for low-voltage applications

This paper has introduced a four-level π-type converter for low-voltage applications which has a simple structure with six switches per phase leg. The line output voltage has seven levels and the output harmonics is much lower than the conventional two-level converter. The switching states and their associated output voltage levels have been analyzed. A simple carrier-based modulation method with zero-sequence signal injection has been devised to modulate the converter and regulate dc-link neutral points´ voltages. The two neutral points´ voltages can be well controlled with a back to back configuration even under high modulation index and high power factor. Simulation and experimental results have validated the topology, modulation and control strategy for the four-level π-type converter.