考虑深层大地电阻率的电网广域直流电流分布数值计算

Computation for Wide-area Direct Current Distribution of Power Grids Considering Deep Earth Resistivity

为解决直流输电大地返回电流导致的电磁兼容问题,全面论述了考虑深层大地电阻率的广域电流场数值计算方案。首先基于场路耦合的方法建立了通用的理论模型,并对模型的简化、等效和信息录入等环节进行了讨论。再结合四极法与大地电磁法从测量方案和反演算法2个方面对大地电阻率的测量问题进行了研究。最后提出了基于自适应采样的复镜像法进行复杂结构的水平多层大地格林函数的高精度计算。算例结果表明,对省级电网的简化可以大大缩减模型的规模,四极法与大地电磁法的测量方案能够完全满足现场应用需求,而自适应采样的复镜像法关于格林函数的最大误差约为10^(-6),精度比高阶复镜像法更高。

To solve the electromagnetic compatibility issues induced by the earth-return current of HVDC transmission, we put forward a numerical method of wide-area current field computation considering the deep earth resistivity. Firstly, a general theoretical model is established based on the field-path coupling method. Moreover, simplification of the model and the feasible input of the wide-area grounding system are discussed. Secondly, both the measurement and inversion have been studied by combining the four-point method and the magnetotelluric method. Finally, a new type of complex image method based on adaptive sampling is proposed to compute the Green＇s fianction accurately. The results show that the AC system of a province can be simplified by nodal equivalence, and the earth resistivity measurement methods of the four-point method and the magnetotelluric method can satisfy the practical demands. In this paper, the maximum error of the complex image method of adaptive sampling is about 10^-6, which is higher than that of the high-order complex image method.