A Four-Level Active Nested Neutral Point Clamped (4L-ANNPC) Converter

The existing four-level nested neutral point clamped (4L-NNPC) converter is a good candidate for medium-voltage motor drive applications. However, the inner two switches per phase leg suffer from high voltage stresses due to the two clamping diodes per phase leg. Besides, the flying capacitors suffer from large low-frequency voltage fluctuations, especially at low frequency operations. To overcome the two problems, a four-level active nested neutral point clamped (4L-ANNPC) converter with a low-frequency fluctuation suppression method is proposed and analyzed in this paper. Compared to the 4L-NNPC converter, the proposed 4L-ANNPC converter realizes uniform voltage stress distribution and small low-frequency voltage fluctuations. Finally, simulation studies are provided and analyzed to verify the proposed topology and the low-frequency fluctuation suppression method.