A Reduced Arm DC-AC Modular Multilevel Converter Topology

This paper presents a new DC to AC Modular Multilevel Converter (MMC) topology. The proposed topology requires lesser number of arms than the traditional MMC to generate equal magnitude and excellent quality of output AC voltage. The positive arm of the proposed converter is having submodules similar to traditional MMC. In contrast, passive tuned LC filters are present in the place of the negative arms in the proposed MMC topology. This helps to generate an equal magnitude of output AC voltage as traditional MMC with half of the input DC bus voltage magnitude. Additionally, traditional MMC requires large number of submodules to generate many voltage levels and hence create small steps in the output voltage matching close to a sine wave. The passive tuned LC filters in the proposed circuit topology are designed to absorb the switching harmonics generated from the positive arms. This makes the output AC voltage very close to a pure sine wave, with highly reduced higher order switching harmonics. This paper explains the operational principle along with the pre-charging of the submodule capacitors at start-up of the new converter. Simulation and experimental studies confirm the operation of the new converter topology.

Automated summary

This paper introduces a new DC to AC Modular Multilevel Converter (MMC) topology that requires fewer arms than traditional MMC to generate high quality output AC voltage. By utilizing passive tuned LC filters in place of negative arms, this new topology reduces switching harmonics and produces output voltage closer to a pure sine wave. Overall, the proposed converter design offers improved output waveform quality with reduced hardware requirements.