基于协同型复合判据的多端直流环网边界保护原理

Boundary Protection Principle of Multi-terminal DC Loop Network Based on

利用直流线路两侧加装的限流电抗器对故障高频分量的阻断特性构造边界保护判据,是多端直流电网实现有选择性故障切除的可行技术路线之一。然而,限流电抗器的选型并不以适配保护的灵敏性为依据,导致现有基于最高特征频带的边界保护原理存在着兼顾选择性及灵敏性的矛盾。为解决上述问题,文中研究借助小波包变换将故障暂态量分解为若干频带,并以保护的安全性、灵敏性为双重约束对频带进行了综合考察及预选;在此基础上,利用D-S证据理论将预选频带的多重信息进行融合,最终得到兼顾低特征频带的高抗扰性以及高特征频带的高灵敏性的复合判据。仿真结果表明,所提出判据能够更灵活地区分区内高阻故障及伴随噪声的区外故障。在大样本随机故障场景下,所提判据比传统保护方案具有更高的动作正确率。

It is one of the feasible technical routes for the selective fault removal of the multi-terminal DC power grid using the blocking characteristics of the current-limiting reactors installed on both sides of the DC line for the high-frequency fault component to construct the boundary protection criterion.However,the selection of current-limiting reactor is not based on the sensitivity match of protections,which leads to the contradiction between selectivity and sensitivity in the existing boundary protection principle based on the highest characteristic frequency band.In order to solve the above problems,this paper uses wavelet packet transform to decompose the fault transient component into several frequency bands,and takes the security and sensitivity of the protection as the dual constraints to comprehensively investigate and preselected the frequency band.On this basis,the D-S evidence theory is used to fuse the multi-information of the preselected frequency band.Finally,a composite criterion which takes into account the high immunity of the low characteristic frequency band and the high sensitivity of the high characteristic frequency band is obtained.The simulation results show that the proposed criterion can flexibly distinguish the internal fault with high resistance and the external fault with noise.In the case of large sample of randomized faults,the proposed criterion can maintain higher correct operation rate than traditional protection scheme.