基于谐波注入的柔性直流系统接地极线路故障测距方法

Fault Location for Grounding Electrode Line of MMC DC System Based on Harmonic Injection

针对基于模块化多电平换流器(modularmultilevel converter,MMC)的直流输电系统,文中利用其灵活可控性,提出了一种基于谐波主动注入的接地极线路测距方法:通过对某一极换流站投入子模块数量的主动控制,改变对应极线直流电压,从而在接地极线路上产生不平衡谐波电流和电压分量;在此基础上,即可实现可靠的故障测距。仿真结果表明,所提出的谐波注入方法能够产生所需的谐波分量,且对系统正常运行影响较小;此外,接地极线路上直流不平衡电流大小对该方法的测距精度影响较小;在高阻接地、近端接地、噪声影响等工况下仍能保持较高的测距精度,最大误差小于1.5%,能够满足接地极线路的测距精度要求。

In this paper, a grounding electrode line fault location method, based on the actively injecting harmonic, is proposed. By controlling the number of the on-state sub-modules in each phase of the converter station, an AC harmonic component can be generated, which is superimposed on the DC voltage of the corresponding pole line. Therefore, the harmonic with the same frequency can be generated in the grounding electrode line. On this basis, the fault location can be realized. The simulation results verified that the accuracy of the proposed method was less affected by the unbalanced current on the grounding electrode line. And the location accuracy is high under the conditions of high-resistance grounding fault and near-end grounding fault. The maximum error is less than 1.5%, which satisfies the fault location requirement of the grounding electrode line. Besides, the method is almost immune to noise.