Abstract:When there is a severe ground fault in AC grid,the modular multilevel converter high voltage direct current (MMC-HVDC) system connected to passive networks will collapse due to the continuous decline of the DC voltage caused by the imbalanced power transfer.Firstly,the discharging mechanism of the capacitors in the MMC is analyzed.Then an AC fault ride-through strategy of the MMC-HVDC system connected to passive networks is proposed,the key of which is to make a balance between the DC power flowing into and out of the MMC-HVDC system through reducing the power absorbed by the passive networks during the fault.Finally,an MMC-HVDC system connected to passive networks,including induction motors and static load models,is established in the PSCAD/EMTDC software,based on which the discharging mechanism of capacitors in the MMC under the condition of ground fault in AC grid is verified.The simulation results demonstrate that,with the help of the proposed fault ride-through strategy,the drop of the DC voltage is mitigated and the MMC-HVDC system operates steadily during the ground fault in the AC system.
肖亮, 徐政, 刘昇, 安婷, 孔明. 向无源网络供电的MMC-HVDC送端交流故障穿越策略[J]. 电工技术学报, 2016, 31(15): 89-98.
Xiao Liang, Xu Zheng, Liu Sheng, An Ting, Kong Ming. AC Fault Ride-Through Strategy of MMC-HVDC Connected to Passive Networks. Transactions of China Electrotechnical Society, 2016, 31(15): 89-98.
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