基于直流电抗器电压的多端柔性直流电网边界保护方案

直流故障的快速可靠识别是多端柔性直流电网亟须突破的关键技术之一。基于线路边界元件直流电抗器的特征,提出了一种新型的多端柔性直流电网线路边界保护方案。利用故障线路和非故障线路直流电抗器电压大小和方向的不同,实现故障线路的快速识别;利用故障线路正、负极直流电抗器电压大小的差异进行故障类型和故障极的判别。该方案仅通过单端直流电抗器的电压即可实现对故障的快速检测、识别,不仅能够满足直流电网对保护的要求,而且保护方案简单易实现,对硬件要求较低,无需通信。最后,在PSCAD/EMTDC中搭建三端柔性直流电网模型,仿真结果验证了该保护方案在不同直流故障和运行情况下的有效性。

Boundary Protection Scheme for Multi-terminal Flexible DC Grid Based on Voltage of DC Reactor

Fast and reliable DC fault detection is one of the key techniques to break through for multi-terminal flexible DC grid. According to the characteristics of the DC reactors on the line, a novel boundary protection scheme is proposed to quickly detect the fault line using the voltage magnitude and direction of the DC reactors. And the fault type and fault pole can be judged with the difference in the voltage of DC reactor between the positive and negative poles of the fault line. The scheme can provide fast DC fault detection and identification just by the voltage of the single-ended DC reactor, thereby meeting the protection requirement of the DC grid while simplifying implementation. For the local fault detection of the proposed scheme, no telecommunication is needed. A three-terminal flexible DC grid model is built in PSCAD/EMTDC for simulation results to demonstrate the effectiveness of the scheme proposed under different DC faults and operating conditions.