Self-Block and Voltage Balance Modular Multilevel Converter Sub Module Topology and Control
Zhang Jianpo1, Cui Diqiong1, Tian Xincheng2, Zhao Chengyong1
1. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Baoding 071001 China; 2. State Grid Tangshan Power Corporation Tangshan 063000 China
Abstract：High-voltage DC transmission based on modular multilevel converters (MMC) needs to deal with possible short-circuit faults on the DC line and the capacitor voltage balance problem caused by too many sub modules. To ensure sub modules working independently as a constraint, the paper first analyzes the full bridge topology fault suppression mechanism. Then a sub module topology with DC link fault blocking and internal capacitor balance ability is designed based on the fault clamp circuit and switch capacitor multilevel ideas. Thus, it will not only meet the self-suppression requirement but also reduce the number of capacitors participating in the sort balancing algorithm to half. What is more, for the self blocking and voltage balance topology, the DC link fault suppression characteristics under two different blocking modes, i.e. self-balancing control strategy based on the voltage level output priority and the unblocking DC link fault suppression strategy, are also studied. Finally, a PSCAD-EMTDC simulation model is used to verify the effectiveness of the proposed topology of DC link fault suppression and control strategy.
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2020, Vol. 35 
