考虑过渡电阻影响的柔性直流配电系统电流突变量保护

A DC Current Derivative Protection With Capability of Resisting High Resistance for Flexible DC Distribution System

柔性直流配电系统中,直流故障下,其换流器自身保护的闭锁速度快,有效故障信息极少,系统保护需要高速检测故障。基于有限的故障暂态信号,研究快速、准确识别故障区域的保护是直流配电系统发展的迫切需求。因此,提出了一种适用于多端柔性直流配电系统的暂态量保护。利用直流双极短路故障后的直流电流波形变化特征,计算电流波形曲率并以此为判据,与电流突变量（di/dt）算法相结合,实现不同过渡电阻故障的快速、可靠识别。该保护基于本地测量实现直流线路保护,计算量小,解决了传统电流突变量保护受过渡电阻故障影响无法正确动作的问题。最后,在PSCAD中搭建精细化多端柔性直流配电系统仿真模型,验证了所提出的电流波形曲率保护方法的动作性能,保障了直流配电系统的安全可靠运行。

Converter is fast in blocking speed when DC line fault occurs in flexible DC distribution system. Therefore, there is too little fault information to achieve DC protection meeting both speed and selectivity requirement. In order to meet selectivity and speed requirement of DC protections, this paper proposed a new protection for multi-terminal DC distribution system. This protection is developed based on natural variation characteristics and curvature of DC current under fault transients. The proposed method could identify faults with different high resistances quickly, meeting speed and reliability requirement of the DC distribution system. Results from PSCAD/EMTDC were evaluated to verify feasibility and superiority of the proposed method.