Xi'an Jiaotong University, Xi'an, Shaanxi, China.
Electric Power Research Institute of Shanghai Electric Power Company, Shanghai, China.
PLoS One. 2019 Jan 10;14(1):e0209548. doi: 10.1371/journal.pone.0209548. eCollection 2019.
Large currents are injected into the earth from grounding poles of HVDC systems under monopole ground return mode. The currents change the earth surface potential and result in DC currents in AC systems. This paper proposes a computationally efficient decoupled circuital calculation method for assessing the unwanted DC currents in AC grids. Firstly, the earth resistive network is acquired by simulating the DC grounding current distribution using Finite Element Method (FEM). Secondly, the earth resistive network and AC grid are combined to develop a decoupled circuital model of the overall system. The acquired model is used to calculate the DC currents in AC grids by solving a set of linear equations. The proposed method is computationally more efficient as compared to field-circuit coupled methods. In addition, its accuracy is proved by showing a close agreement between our results and field-circuit coupled model as well as the actual measurements. Finally, in Shanghai area power grid the DC currents are calculated using the proposed technique. Based on these calculations, remedial measures for reducing the DC currents in AC grid are suggested. Our research results indicate that DC currents in AC systems can be reduced by operating the two HVDC projects with opposite polarities.
在单极大地回线方式下，高压直流（HVDC）系统的接地极会向大地注入大电流。这些电流改变了大地表面的电势，导致交流系统中出现直流电流。本文提出了一种计算效率高的解耦电路计算方法，用于评估交流电网中不受欢迎的直流电流。首先，通过使用有限元方法（FEM）模拟直流接地电流分布来获得大地电阻网络。其次，将大地电阻网络与交流电网相结合，开发出整个系统的解耦电路模型。通过求解一组线性方程，利用所获得的模型来计算交流电网中的直流电流。与场路耦合方法相比，该方法具有更高的计算效率。此外，通过将我们的结果与场路耦合模型以及实际测量结果进行比较，证明了其准确性。最后，使用所提出的技术计算了上海地区电网中的直流电流。基于这些计算结果，提出了减少交流电网中直流电流的补救措施。我们的研究结果表明，通过运行两个极性相反的 HVDC 项目，可以减少交流系统中的直流电流。
