考虑高阻故障的多端直流电网快速保护方案

A Fast Protection Scheme for Multi-Terminal DC Grid Considering High Resistance Faults

针对含限流电感的多端直流电网,提出了一种考虑高阻故障的快速保护方案。该方案以线路附加电感前端的电压变化率作为主判据,并增加了基于小波高频能量的高阻故障辅助判据。辅助判据通过平稳小波变换提取时窗内初始故障波和反射波的高频特征量,从而有效地提高保护在高阻故障下的灵敏度。保护方案的主判据和辅助判据在动作速度和耐受过渡电阻能力方面形成互补,且仅由本地量构成,无通信延时,能够满足多端直流电网对保护速动性和可靠性要求。最后,基于PSCAD/EMTDC搭建四端直流电网,仿真结果证明了本文所提方法的有效性。

A fast protection scheme considering high-resistance fault is proposed for multi-terminal DC grid with current limiting inductance.The rate of change of voltage measured at the front-end of current limiting inductance is used as the main protection criterion in the new algorithm,and an auxiliary criterion,which uses the wavelet-based high frequency energy,is added to improve the performance of protection under high resistance faults.The auxiliary criterion extracts the high-frequency characteristics of the initial and reflected traveling waves by using stationary wavelet transform(SWT),and can improve the sensitivity of the protection significantly under high resistance faults.The main and auxiliary criterion of the protection scheme complement each other in terms of speed and tolerance to fault resistance.In addition,the protection scheme only utilizes the local signals,and thus has no signal communication delay,which can satisfy the requirement of protection speed of multi-terminal DC grid.At last,a four-terminal DC grid is modeled based on PSCAD/EMTDC simulation platform,and substantial simulation results verify the effectiveness of the proposed method.