基于临界阻抗边界的多馈直流系统同时故障风险评估

Critical Impedance Boundary-Based Risk Assessment on Simultaneous Faults in Multi-Infeed DC Transmission System

目前多馈直流输电系统同时故障风险评估主要依赖时域暂态仿真扫描计算来确定,该方法计算量大,耗时长,难以满足系统规划运行方式灵活多变的应用需求。引入节点电压影响因子(voltage influencing factor,VIF)定义,推导建立换流站母线电压跌落比的节点阻抗表达式,以临界电压跌落阀值为判据,划出各直流换流站的临界故障阻抗边界,根据各直流的临界故障阻抗边界重叠情况可准确、快捷、直观地给出多馈直流系统发生同时故障的风险评估结论。通过实际系统的时域仿真结果对比,验证了该方法的有效性,可应用于电力系统规划、设计及运行等领域。

At present the risk assessment on simultaneous faults occurred in multi-infeed DC transmission system is mainly performed by use of time-domain transient simulation tolls.In view of heavy computational burden and long computation time,it is difficult to meet flexible and changeable application requirements of power system planning and operation.Leading in the definition of nodal voltage influencing factor（VIF）,the expression of nodal impedance matrix for bus voltage drop ratio of converter substation is derived,and taking critical voltage drop threshold as criterion,the boundaries of critical fault impedances of converter stations are determined and according to overlap of critical fault impedance boundaries of converter stations the risk assessment of simultaneous faults occurred in multi-infeed DC transmission system can be concluded fast,accurately and intuitively.Taking an actual multi-infeed DC transmission system in Guangdong power gird for example,the effectiveness of the proposed method is verified by comparing risk assessment results with time-domain simulation results.