基于双树复小波变换的混合直流输电线路行波保护方法

Traveling Wave Protection for Hybrid HVDC Transmission Lines Based on Dual-tree Complex Wavelet Transform

首先分析了混合直流输电线路故障特征,并以葛南工程为例,搭建了混合直流输电系统电磁暂态仿真模型。理论与仿真分析表明,直流电压共模量和差模量之间相互解耦,且故障前后特征差异显著,该参数可用于混合直流输电线路保护。其次,研究了双树复小波变换在混合直流输电线路保护中的应用,仿真计算表明,利用直流电压差模量二层分解量可作为区分混合直流线路区内外故障的依据。同时,根据直流电压共模量三次方积分值的极性,可以实现故障线路选极。基于以上分析,提出了基于双树复小波变换的混合直流输电线路行波保护方法,该方法能够快速可靠地识别出线路区内外故障,并对高阻接地故障有较高的灵敏度,该方法通过了仿真验证。

Firstly,the fault characteristics of hybrid HVDC transmission lines are analyzed.Taking Gezhouba-Nanqiao(Shanghai)Project as an example,an electromagnetic transient simulation model of hybrid HVDC transmission system is built.Theoretical and simulation results show that the common modulus and differential modulus of DC voltage are decoupled from each other with significantly different characteristics before and after fault.This DC voltage parameter can be used for HVDC line protection.Secondly,application of dual-tree complex wavelet transform in HVDC line protection is studied.Simulation results show that the two-level decomposition of DC voltage differential modulus can be used as the basis for distinguishing the internal and external faults of HVDC line.At the same time,according to the polarity of the cubic integral value of the common modulus of DC voltage,fault line pole selection is realized.Based on above analysis,a traveling wave protection method for hybrid HVDC transmission lines based on dual-tree complex wavelet transform is proposed.The method can quickly and reliably identify the faults inside and outside hybrid HVDC transmission lines with higher sensitivity for high resistance grounding fault,and is verified with simulation.