柔性直流换流站对传统选相方法的影响分析及对策

Influence of the Integration of MMC-HVDC Station on Traditional Phase Selection Method and the Countermeasure

基于电力电子器件的柔性直流换流站与常规同步电源故障电流特征差异较大,导致传统选相方法存在适应性问题。首先研究了换流变压器阀侧Y形联结和D形联结时交流输电线路换流站侧的故障电流特征,得出故障电流的解析表达式。基于此,推导并分析不同跌落深度、电压不平衡度、不同控制目标等因素对相电流差突变量选相方法和电流序分量选相方法性能的影响。为了能适应柔性直流换流站,分析保护安装处与故障点处的电压序分量关系,据此提出一种基于保护安装处电压序分量的选相方法。在PSCAD/EMTDC中搭建仿真平台,测试传统选相方法的适应性和该文所提选相方法的有效性。

Fault current characteristics of high voltage direct current transmission based modular multilevel converter(MMC-HVDC)station based on power electronic devices are very different with that of conventional synchronous source,which results in the adaptability problem of traditional phase selection method.The fault current characteristics of converter station side of ac transmission line is analyzed under wye configuration and delta configuration for converter transformer valve side,and then the analytical expression of fault current is obtained.The effects of voltage sag depth,voltage unbalance degree,different control targets on the performance of two traditional phase selection method,i.e,the phase selection method based on the sudden-change of two-phase current difference and the phase selection method based on current sequence components,are derived and studied deeply.The relationship of voltage sequence components between relay location and fault location is analyzed.Hereby a novel phase selection method based on voltage sequence components of relay place is presented,which can adapt to MMC-HVDC station.A simulation platform is set up and then the adaptability of traditional phase selection method and the effectiveness of the proposed novel phase selection method are tested.