中文摘要：

为揭示直流系统运行方式与变压器直流偏磁现象之间的内在联系,基于宜昌电网的实际参数和PSCAD/EMTDC电磁暂态仿真平台,采用交流系统网络化建模的方法,建立了包含宜昌电网两条500 k V直流输电线路以及接地极临近区域220 k V交流变压器的直流偏磁电流分布仿真模型。对给定工况下变压器中性点直流电流的分布情况进行了仿真,并与现场实测的数据进行了对比验证,还分别对单接地极场景以及双接地极场景时各个特征变电站主变中性点直流电流分布情况进行仿真,揭示了变压器中性点电位差是决定其直流电流分布特征的根本原因。结果表明：所建立模型的误差在10%以下,具备复现系统实际运行情况的能力。分析结果能够为从系统运行角度抑制直流偏磁提供理论依据。

英文摘要：

Theoretical fundamentals of mitigating DC bias current for smooth system operation are seldom researched. We have validated and verified the relationship of system DC bias current of power transformer and system operation mode. The simulation model based on PSCAD/EMTDC contains two 500 k V DC transmission lines and 220 k V transformers adjusted to grounding pole and is built up by using the method of AC system network modeling. By DC bias current distribution simulations, it is found that the developed simulation model has an error margin of less than 10% and has the ability to recur the actual operational scenarios. Comparison is performed on DC current distribution scenarios among the neutral points of specific transformers under the conditions of single grounding pole and dual grounding pole. It is revealed that the potential difference decides the mechanism of various distribution characteristics of DC current through transformer neutral points, which provides the theoretical fundamentals for mitigating the DC bias current for the smooth system operations.