基于HHT的微电网差分能量保护策略

针对微电网双向潮流和并网/孤岛运行时故障电流差异大的特点,在微电网差动保护的基础上,提出了基于HHT变换的差分能量保护新方法。对故障线路两端电流进行时-频变换(HHT变换)获得Hilbert谱,并计算谱能量,利用差分能量是否超出阈值判断是区内故障还是区外故障,且不同故障类型阈值无需改变。在PSCAD中搭建10 kV微电网模型并在Matlab中进行算例验证。大量仿真表明此方法能够可靠检测出并网和孤岛两种运行状态下的各种故障,而且有效解决了高阻抗故障(HIF)保护失效问题。

Microgrid protection using Hilbert-Huang transform based-differential energy scheme

The study presents a new HHT-based method of differential energy protection on the basis of the microgrid differential protection, aiming at the features of microgrid bi-directional power flow and large difference in fault current when operating in grid-connected and islanded modes. Hilbert spectra are obtained by Hilbert-Huang Transform (HHT) of the currents at both ends of the faulty line, and the spectrum energy is calculated. Whether it is an intra-area or out-area fault can be decided by checking if the differential energy exceeds the threshold, without needing to change the thresholds of different fault types. A 10 kV microgrid model is set up in PSCAD and example validation is conducted in Matlab. A large number of simulations demonstrate that this method can reliably detect all kinds of faults under both grid-connected and islanding operation conditions and effectively solve the problem of High Impedance Fault (HIF) protection failure. This work is supported by Youth Science Fund of National Natural Science Foudation of China (No. 61403127).