不依赖边界元件的柔性直流电网反时限过流保护配置方案

现阶段柔性直流电网线路保护大多依赖边界元件,不适用于线路间无明显边界的“网孔结构”柔性直流电网。针对此类电网在远距离输电场景下的线路保护问题,提出了一套不依赖于边界元件的反时限过流保护配置方案。首先,通过分析故障电流的暂态特性,确定了不同故障位置下保护配置的思路。然后,基于保护要求,利用故障电流的波头特征,构造电阻补偿系数保证方案的耐过渡电阻能力,建立了适用于柔性直流电网故障特性的反时限过流保护动作方程,并确定了延时的计算和整定原则。最后,基于PSCAD/EMTDC仿真平台验证了该方案的有效性和适用性。结果表明,所提方案能够准确、可靠地识别故障,具有较强的耐过渡电阻能力。

Inverse time overcurrent protection configuration scheme for a flexible DC power grid independent of boundary components

At present, the line protection of a flexible DC grid mostly depends on boundary components. This is not suitable for a "mesh structure" flexible DC grid with no obvious boundary between lines. Given the problem of line protection in long-distance transmission, an inverse time overcurrent protection configuration scheme independent of boundary components is proposed. First, by analyzing the transient characteristics of fault current, the requirements of protection configuration in different fault locations are determined. Then, based on protection requirements and using the wave head characteristics of fault current, the resistance compensation coefficient is constructed to ensure the resistance to transition resistance of the scheme. The action equation of inverse time overcurrent protection suitable for the fault characteristics of a flexible DC grid is established, and the calculation and setting principle of time delay are determined. Finally, the effectiveness and applicability of the scheme are verified based on the PSCAD/EMTDC simulation platform. The results show that the proposed scheme can accurately and reliably identify faults and has strong resistance to transition resistance.