Lin Lin1, Pei Zhongchen1, Cai Guowei1, Liu Chuang1, Pei Yong2
1. School of Electrical Engineering Northeast Electric Power University Jilin 132012 China; 2. State Grid Fushun Electric Power Company Fushun 113000 China
Abstract：Thanks to the advantages such as multi-ports, modular topology, easy to achieve voltage level expansion and high quality of output waveform, the power electronic transformer (PET) based on modular multilevel converter (MMC) has received widespread attention. However, because the voltage on the MVAC (medium-voltage alternating current) side is created by the MVDC (medium voltage direct current) bus, the voltage of MVAC port is always lower than the MVDC port voltage. Combining with the modular topology and single-stage power conversion ideas, this paper proposed a hybrid isolated modular multilevel converter (HI-MMC). Firstly, the HI-MMC structure as well as the topology and modulation strategy of two isolated sub-modules in HI-MMC was analyzed. Through the combination of two different sub-modules, HI-MMC could break through the limitation of voltage ratio and realize the flexible design of the voltage level in each port. Moreover, HI-MMC has main advantages of single-stage power conversion, simple control system and capacitance saving. Secondly, the corresponding configuration schemes of various sub-modules under different voltage ratios were studied, and the average equivalent model of single-phase HI-MMC system was established. Finally, the experimental results on a scaled-down 10kW HI-MMC prototype show that the proposed circuit topology is feasible and effective.
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2021, Vol. 36 
