基于限流电抗器电压的直流配电网单端量保护

Single-terminal Protection for DC Distribution Network Based on Current Limiting Reactor Voltage

直流配电网故障特性复杂,故障电流上升速度快且峰值大,快速、灵敏的故障识别与线路保护是保障直流配电网安全运行的关键技术之一。为此,针对增设限流电抗器的直流配电网,提出一种利用限流电抗器电压实现高灵敏故障识别的直流配电网单端量保护方案。首先,通过分析含限流电抗器的直流配电网故障特性,明确区内、区外故障时限流电抗器电压的特征差异。其次,研究限流电抗器对故障特性及直流保护的影响机制,提出虚拟补偿策略以增强故障识别的灵敏性。在此基础上,根据线路电压变化率设计保护启动判据,提出基于虚拟补偿的故障识别判据和故障选极判据,并给出完整的保护方案流程。最后,基于PSCAD/EMTDC仿真平台进行大量的仿真测试,结果表明所提保护方案能够实现对直流故障的快速准确判断,无需通信支持,且对过渡电阻、噪声及负荷波动具有较强的耐受能力。

In the DC distribution network,the fault characteristics are complex.The DC fault current rises rapidly,and the peak value is significant.Fast and sensitive fault identification and line protection are the key technologies to ensure the safe operation of the DC distribution network.Thus,a single-terminal protection strategy for the DC distribution network by utlizing current limiting reactor voltage is proposed for the DC distribution network with additional current-limiting reactors,which can sensitively identify faults.Firstly,the characteristic difference of current limiting reactor voltage during internal and external faults is clarified by analyzing the fault characteristics of the DC distribution network with current limiting reactors.Secondly,the influence mechanism of the current limiting reactor on the fault characteristics and DC protection is analyzed in detail,and a virtual compensation strategy is proposed to enhance the sensitivity of fault identification.On this basis,the protection starting criterion is designed according to the change rate of line voltages,the fault identification criterion and fault pole selection criterion based on virtual compensation are proposed,and the complete protection scheme is given.Finally,based on the PSCAD/EMTDC platform,a large number of simulation tests have been carried out.The results show that the proposed protection can achieve fast and accurate fault determination with strong tolerance to transition resistance,noise,and load fluctuations.