基于感性模糊识别的MMC直流输电线路单极接地故障分析

Single pole-to-ground fault analysis of MMC DC transmission lines based on inductance fuzzy identification

伪双极模块化多电平换流器(MMC)直流输电系统发生单极接地故障时的故障电流较小,在高阻故障下故障电流更是极其微弱,很难快速识别单极接地故障。考虑MMC直流输电系统中,单极接地故障暂态过程与其他类故障暂态过程的故障回路的区别,提出一种基于感性模糊识别的单极接地故障识别方法。利用电流变化率与电压的相关系数近似表征回路测量点的电感特征,定义正、负极相关系数的比值为感性模糊系数。根据感性模糊系数的符号识别单极接地故障,然后根据感性模糊系数的绝对值判断故障极。大量仿真实验表明,所提方法有较强的速动性和灵敏性,并有很强的耐受过渡电阻能力。

Fault current of pseudo-bipolar MMC(Modular Multilevel Converter)DC(Direct Current)transmission system is relatively small under single pole-to-ground fault,and becomes extremely small under highresistance fault,so it is difficult to identify single pole-to-ground fault quickly.Considering that for MMC DC transmission system,the characteristics of fault circuit in transient process of single pole-to-ground fault are different from that of other faults in MMC DC transmission system,a single pole-to-ground fault recognition method based on inductance fuzzy identification is proposed.The correlation coefficient between current change rate and voltage is used to approximately represent inductance characteristics at the loop measurement points.Meanwhile,the ratio of positive and negative correlation coefficients is defined as the inductance fuzzy coefficient.The single pole-to-ground fault is identified according to the sign of inductance fuzzy coefficient,while the fault pole is identified according to the absolute value of inductance fuzzy coefficient.A large number of simulation show that the proposed method has high speed and sensitivity and strong antitransition resistance ability.