基于电网N-1数据反演交流电网中直流电流分布的土壤等效电阻模型研究

为了解决直流偏磁研究中无法准确建立土壤模型的问题，提出了一种基于电网N-1原则将电网多次多点测量数据与仿真计算相结合的土壤等效电阻模型建模方法，用以计算交流电网中的直流电流分布数据。该方法在已知交流系统网络参数的情况下，通过依次开断建模范围内两变电站间的交流输电线路，测得多组交流电网中直流电流的分布数据，利用矩阵运算或遗传算法反演土壤等效电阻模型。针对某直流接地极近区交流电网建立土壤等效电阻模型仿真算例，分析计算在直流输电系统单极大地运行情况下，该地区交流电网中直流电流的分布情况。结果表明，采用土壤等效电阻模型所得的计算结果能够逼近实际数据，且模型受交流系统拓扑结构的影响较小，能够在土壤构成复杂的情况下，保持计算误差在允许的范围内。仿真算例进一步验证了土壤等效电阻模型建模方法的正确性。基于电网N-1数据反演土壤等效电阻模型的建模方法，避免了复杂的电场计算，无需收集土壤参数且计算结果准确，具有一定的工程实用价值。

Study on Soil Equivalent Resistance Model Inversion for DC-bias Distribution Based on Grid N-1 Changing Principle in AC Power System

In order to solve the problem that the soil model cannot be established accurately in the study of DC-bias, a soil equivalent resistance model based on N-1 principle was proposed, which combines the multiplemeasured data and simulation calculation of the power gridto calculate DC current distribution data in AC system. With known AC grid parameters, the multi-group distribution data of DC-bias current in AC power grid were obtained when the transmission line between two substations was put out of service in turn. The accurate equivalent resistance of soil model could be deduced by using matrix operation or genetic algorithm. A simulation example of soil equivalent resistance model was established for AC power grid near a grounding electrode, and the distribution of DC-bias current in the AC power grid was calculated while the HVDC transmission system operates under monopole ground return mode. The results indicated that the calculation data obtained from the soil equivalent resistance model are more close to the measured data. This model is less affected by the topology of the AC system and can keep the calculation error within the allowable range when the soil composition is complex. It is thus clear that the correctness of the modeling method is proved by the example. The modeling method of soil equivalent resistance based on N-1 changing principle of the power grid, avoids complicated calculation of electric field and does not need to get soil parameters. It has certain practical value in engineering projects.