行波波头的参数识别方法在高压直流输电系统中的应用

Parameter Identification Method with Applications to Traveling Wave Head in VSC-HVDC

为了提高识别电压源换流器型高压直流输电(VSC-HVDC)系统中的行波波头的可靠性,提出了一种行波波头的参数识别方法。根据VSC-HVDC系统零模网络的分析结果,直流线路两端的系统可以等效为电容,利用保护安装处测得的零模电压和零模电流可以计算零模识别电容。当直流线路发生故障后,零模识别电容会在行波波头到达线路两端的时刻突变至等效电容,因此可以根据零模识别电容的突变时刻确定行波波头的到达时刻。仿真结果表明:对于全长为100km的线路,采用行波波头的参数识别方法,故障定位的绝对误差小于200m,说明该方法具有较高的识别精度。与传统的行波波头识别方法相比,文中方法的优势在于能够始终可靠识别VSC-HVDC系统中行波波头的到达时刻,不受电气量波形渐变和输电线路参数频变的影响,且适用于高阻接地故障,能够应用于VSC-HVDC直流线路区内接地故障的定位,因此具有一定的理论和实用价值。

In voltage source converter based high voltage direct current（VSC-HVDC）system,the zero-sequence network at both ends of the DC line can be equivalent to a parallel capacitor,which reduces the slope of voltage traveling waveform to difficultly identify the traveling wave head with electrical quantities.A method is proposed to identify the arriving time of traveling wave head via judging the sudden changing time of the calculated zero-sequence capacitance.The method is used to locate fault points in the DC line of VSC-HVDC system of 100 km,and the absolute location error can be limited within range of 200 m.The theoretical analysis and simulations show that the proposed method is reliable and accurate to identify the arriving time of the traveling wave head,especially,it is immune from the slow change of electrical quantities and the frequency dependent characteristics of DC lines and suitable for high resistance grounding cases.