Abstract: The multilevel converters receive wide acceptance in industry and energy systems because they enable the design of medium and high voltage systems with excellent output voltage quality. Among the different topologies for multilevel converters, multicell converters feature the highest degree of modularity and the lowest expense for redundancy due to the large number of cells they have, as well as the lowest harmonic content due to the large number of output voltage levels they produce. In this paper a Four-cell Nine-level DFCM Converter is explained.The main advantages of this converter, in comparison with FCM, are doubling the rms and the number of output voltage levels and improving the output voltage frequency spectrum. Moreover the number of high frequency switches,flying capacitors and input dc voltage sources are reduced by 50%.This converter is controlled by modified phase-shifted pulsewidth modulation technique.The Four-cell nine-level DFCM circuit is simulated in MATLAB software and simulation results are presented to validate the effectiveness and advantages of the respective configuration and the THD for the converter was found to be less than 1%(which meets the harmonic standards of IEEE).

Keywords: Flying capacitor multicell (FCM) converter, phase shifted pulsewidth modulation (PSPWM), natural balance, stacked multicell (SM) converter).