MMC对交流系统三相短路故障短路电流影响的机理研究

Analysis of the Short-circuit Current of MMC-HVDC

该文从柔性直流输电系统运行控制原理出发,分析得到柔性直流电网换流站近区发生三相短路故障后,换流站提供短路电流的特征,并在PSCAD上搭建模型进行仿真验证。研究发现,短路故障发生后,柔性直流换流站呈电流源特性,提供的短路电流分为暂态过程和稳态过程两个阶段。故障发生控制系统响应后,换流站提供的短路电流是三相对称交流量,不存在直流分量。短路电流暂态过程与换流站的控制参数有关,而短路电流稳态值的大小与换流站的控制方式、运行模式以及换流站控制器的控制参数密切相关。该研究可以为今后柔性直流输电工程建设中控制参数的设定,以及柔性直流输电工程换流站接入点的选择提供参考。

Short circuit current characteristics of modular multilevel converter （MMC） have been studied in this paper. First of all, this paper introduced the principle of MMC. Furthermore, the injection short circuit current characteristics of MMC were analyzed. When the three-phase short circuit fault occurs near the converter station, the MMC will supply circuit current, and the converter station presents the current source characteristics There are two stages of the short circuit current. The first is the transient process. After the controllers working, it is totally different from generator, and then there is no DC component anymore. The second is the steady - state stage. The size of short circuit current is related to the control schemes, operation mode and control parameters of MMC. Through comparison with and analysis of the testing results on a typical system, it is shown that the proposed characteristics are accurate. The research result offers a reference of construction of power grid.