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High power DC/AC/DC converter based on different modulation strategies

The recent researches on high voltage and power DC/DC converter mainly focus on topology. The newest topology based on modular multilevel converter(MMC) is composed of a transformer coupling two three-phase MMC, so that it can be easily extended according to the required voltage rating. However, the present topology almost adopt the same modulation strategy at two sides of converter. Because of the different applications of the high power DC/DC converter, the voltages on two sides will be different leading to the number of submodules (SM) different. For the different structure mentioned above, this paper presents the method which takes different modulation strategies at two sides of converter. It respectively selects the optimal modulation strategy according to the SM number at two sides, which could reduce switching losses and harmonic content. Finally, a simulation model of 5kV/500V DC/AC/DC converter is established in MATLAB/Simulink, which verifies the feasibility of the method.