计及柔性直流的系统短路电流实用计算方法

Practical Calculation Method for Short-circuit Current of System Considering VSC-HVDC

柔性直流输电可实现故障穿越,在交流系统发生短路故障后持续运行。随着柔性直流输电日趋广泛的工程应用,其对系统短路电流的影响不容忽略。针对含有柔性直流输电接入的交流系统缺乏准确实用的短路电流计算方法问题,分析了交流系统发生短路故障后柔性直流注入系统电流特征。基于柔性直流的控制策略,研究了短路电流计算过程中柔性直流等效电流源设计,分析了电流源幅值设定的合理性。在弱化柔性直流输出电流与并网点电压耦合作用的基础上,提出了基于叠加原理的计及柔性直流输电的三相交流短路电流计算方法。最后,搭建测试系统,通过电磁暂态仿真验证了所提方法的有效性。

The voltage source converter based high voltage direct current transmission(VSC-HVDC)can achieve fault ride-through and continue to operate after a short-circuit fault occurs in the AC system.With the increasingly widespread engineering applications of VSC-HVDC,its influence on the short-circuit current of the system cannot be ignored.Aimed at the lack of an accurate and practical short-circuit current calculation method for AC system connected with VSC-HVDC,the current characteristics of VSC-HVDC injection system after the short-circuit fault occurs in the AC system are analyzed.Based on the control strategy for VSC-HVDC,the design of a VSC-HVDC equivalent current source in the process of short-circuit current calculation is studied,and the rationality of current source amplitude setting is analyzed.On the basis of weakening the coupling effect between VSC-HVDC output current and the voltage at grid-connected point,a three-phase AC short-circuit current calculation method considering VSC-HVDC is proposed,which is based on the superposition principle.Finally,a test system is built,and the effectiveness of the proposed method is verified by electromagnetic transient simulation.