基于触发角变化特性的高压直流线路纵联保护

Pilot protection of HVDC power transmission lines based on variation characteristics of firing angle

现有的行波保护和电流差动保护间的配合存在延时,使得故障过程中的直流控制暂态阶段缺乏相应的保护。基于控制保护融合的思路,利用故障后直流控制暂态阶段两换流站侧的触发角变化特征,提出一种基于触发角变化特性的高压直流线路纵联保护新原理。通过构造整流侧和逆变侧的触发角变化率均值间的余弦相似度判据和固定时间间隔的触发角变化量判据,实现区内外故障的准确识别。PSCAD/EMTDC仿真结果表明,所提方案可在直流控制暂态阶段识别故障,耐受过渡电阻能力强,动作速度较快,且数据采集不需要严格同步,可作为高压直流线路的快速后备保护。

There exists a matching delay between the traveling wave protection and the current differential protection,which leads to the lack of protection during the transient process of DC control.Based on the idea of control and protection combination,a new principle of pilot protection for HVDC power transmis⁃sion lines is proposed by using the changing characteristics of the firing angle at two converter stations in the transient process of DC control after fault.In the protection,the cosine similarity criterion between the mean values of the firing angle changing rate of the rectifier and inverter stations and the firing angle variation criterion with the fixed time interval are constructed to identify the internal and external faults.The simulative results of PSCAD/EMTDC show that the proposed scheme can identify the faults in the tran⁃sient process of DC control with fast motion speed and strong ability to withstand transition resistance,and it does not need strict synchronization of data acquisition.Therefore,the proposed scheme can be used as a fast backup protection for HVDC lines.