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基于模块化多电平换流技术的分区互联装置在城市电磁环网解环方面具有广阔的应用前景,该文重点研究单变压器分区互联装置交流系统单相接地故障和直流系统单极控制接地故障的故障特性.针对交流单相接地故障引起零序电压问题,分析零序电压对故障穿越策略的影响,提出零序电压策略,降低故障情况下的直流侧过电压水平.针对直流单极接地故障引起的交流电流直流偏置问题,分析交流电流直流偏置机理,推导故障情况下交流电流的数学表达式,提出基于切除子模块和闭合子模块旁路开关的保护动作策略.在PSCAD/EMTDC中建立单变压器分区互联装置系统模型,通过仿真分析验证保护控制策略的正确性.“,”Modular multilevel converter (MMC) based interconnecting device has a promising future in open-loop for urban electromagnetic loop.This paper mainly studies fault characteristic of single transformer interconnecting device under ac and de grounding fault.In view of zero sequence voltage caused by the single line to ground fault at transformerless side,the impact of zero sequence voltage to fault ride though strategy was analyzed and zero sequence voltage controller was proposed,which could reduce overvoltage level in the dc side.In view of DC bias in the AC current caused by the DC pole to ground fault,fault mechanisms were analyzed and mathematic expression of fault components were derived.Control and protection scheme was proposed based on bypassing submodule or closing submodule bypass switch.Simulation results based on a PSCAD/EMTDC model prove the control and protection scheme is validity.