DC Fault Detection in Meshed MTDC Systems Based on Transient Average Value of Current
DC Fault Detection in Meshed MTDC Systems Based on Transient Average Value of Current
复制标题
基于电流暂态平均值的网状 MTdc 系统直流故障检测
DOI：
10.1109/tie.2019.2907499
复制
发表时间：
2020
影响因子：
7.7
通讯作者：
Zhao Xu
中科院分区：
文献类型：
--
作者：
Yujun Li;Jiapeng Li;Liansong Xiong;Xian Zhang;Zhao Xu
对于基于电压源变换器（VSC）的多端直流电网来说，在直流故障发生后的几毫秒内隔离直流故障线路具有重要意义。现有的保护方案和故障分析方法主要基于数值模拟，缺乏理论分析。本文首次提出了一种用于初始直流故障电流计算的基于vsc的MTdc电网高频等效模型。该模型将并联的vsc电容器视为短路，将故障直流线路和健康直流线路的初始故障电流计算简化为简化的RL和RLC电路。在此基础上，进一步提出了一种新的基于vsc的MTdc系统直流故障检测方法。该方法利用线路电流暂态平均值进行一次检测，仅利用一端信息即可快速识别出故障直流线路。此外，还对基于分布参数线模型的暂态故障电流计算与基于集总参数线模型的暂态故障电流计算进行了误差评价。在PSCAD/EMTdc中进行的大量仿真研究表明，所提出的高频等效模型可用于VSC-MTdc系统的初始直流故障分析，所提出的保护方案在不同故障位置和高故障电阻下都是有效的。与传统的基于电流变化率的保护方案相比，该保护方案的采样频率相对较低，计算量较小，具有较高的容错能力和对缺失数据的鲁棒性。
It is of great significance for a voltage source converter (VSC)-based multiterminal dc (MTdc) grid to isolate the dc fault lines within several milliseconds after dc fault. Existing protection schemes and fault analysis methods are mainly based on the numerical simulations, which lack the theoretical analysis. In this paper, a high-frequency (HF) equivalent model of VSC-based MTdc grid that is utilized for initial dc fault current calculation is first proposed. In the proposed model, the parallel connected capacitors of VSCs are regarded as short-circuited, and the initial fault current calculation of the fault dc line and the healthy dc line can be reduced as a simplified RL and RLC circuit. Accordingly, a novel dc fault detection method for VSC-based MTdc system is further proposed. In the proposed approach, the primary detection utilizes the transient average value of line current and the fault dc line can be identified quickly with only one-end information. In addition, the errors between the transient fault current calculation based on the distributed parameter line model and the lumped parameter line model are also evaluated. Numerous simulation studies carried out in PSCAD/EMTdc have demonstrated that the proposed HF equivalent model can be utilized for initial dc fault analysis of VSC-MTdc system and the proposed protection scheme is effective under different fault locations and high fault resistances. Compared with the traditional protection schemes based on rate of change of current, the proposed one requires relatively low sampling frequency and low computation burden, and has high fault resistance tolerance ability and high robustness with respect to the missing data.