基于突变能量比值的多端柔性直流电网闭锁式纵联保护方案

Blocking pilot protection based on ratio of superimposed energy for VSC-MTDC grid

多端直流电网中的限流电抗器集中配置,直流线路之间边界元件的缺失将使区内、区外故障的辨别变得困难。针对上述多端柔性直流电网,提出了一种基于突变能量比值的闭锁式纵联保护方案。以保护安装处的突变能量作为启动判据检测直流电网中的故障,利用故障前、反行波在换流站两侧的突变能量比值差异构造保护动作判据。双端保护判断完成后,仅需进行逻辑交换即可决定是否执行跳闸。在PSCAD/EMTDC平台上验证了所提保护方案的有效性,仿真结果表明该保护方案能够有效辨别区内、区外故障,并拥有较好的耐过渡电阻能力和抗噪声能力。

When the current limiting reactor in the multi-terminal DC grid is designed for centralized confi-guration,the lack of boundary elements between the DC lines will make it difficult to distinguish internal and external faults.Aiming at the above-mentioned VSC-MTDC grid,a blocking pilot protection scheme based on the ratio of superimposed energy is proposed.The superimposed energy in the protection installation site is used as the start-up criterion to detect the fault in the DC grid,and the protection action criterion is constructed by using the difference between the ratio of superimposed energies of forward and backward traveling waves at two sides of the converter station.A logical exchange can be made to determine whether to perform a trip or not after the judgment of two-terminal protection is completed.The effectiveness of the proposed protection scheme is verified on the PSCAD/EMTDC platform.The simulative results show that the proposed protection scheme can effectively distinguish internal and external faults with better resis tant capability to transition resistance and noise.