Improved Topology of Modular Multilevel Converter and Application
Zhang Jianpo1, Zhao Chengyong1, Sun Haifeng1, Huang Xiaoming2, Lu Yi2, Qiu Peng2
1. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Baoding 071001 China; 2. State Grid Zhejiang Electric Power Corporation Research Institute Hangzhou 310014 China
Abstract:Modular multilevel converter(MMC) based on cascaded connection of sub modules per phase arm is a newly introduced topology of multilevel converter for multilevel converters with potential for medium voltage and high voltage applications with advantages as high modularity, longer maintenance intervals, low generation of harmonics, etc. However, MMC by itself, is defenseless against DC faults, during such faults, the anti-parallel diodes conduct as rectifier bridges because the fault current continues to be fed, and so the application especially in the high voltage direct current (HVDC) transmission is affected. In this paper, different topologies of sub modules(SM) of MMC are analyzed, according to the relationship between arm current and the capacitance voltage, the series connected double SM(SDSM) is designed, the DC current blocked capability is realized without changing the control strategy. At last, the simulation model is built based on this new topology, the DC current fault characters and the control strategy is analyzed.
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