高压直流输电线路入口端谐波阻抗特性研究

Research on the characteristics of harmonic impedance at the inlet of HVDC transmission line

空充变压器时直流线路沿线的50 Hz谐波分量分布与直流线路入口端谐波阻抗有关。针对直流线路入口端谐波阻抗特性展开详细研究。分析了不同直流运行方式下的直流线路入口端谐波阻抗,定性对比其大小关系。研究了直流线路入口端谐波阻抗的解析等值模型,并基于实际直流系统仿真模型,分别通过解析等值法和测试信号法对不同运行方式下的直流线路入口端谐波阻抗进行计算,验证该解析等值模型的准确性。进一步地,根据计算结果分析直流运行方式对直流线路入口端谐波阻抗大小的影响,所得结论与前文定性分析一致。改变换流器模型中换流变套管杂散电容的大小,研究杂散电容对直流线路入口端谐波阻抗的影响,实现了解析等值模型的简化。

The 50 Hz harmonic component distribution along HVDC transmission line when energizing a no-load transformer is related to the harmonic impedance at the inlet of HVDC line. This paper studies the characteristics of harmonic impedance at the inlet of HVDC transmission line in detail. The harmonic impedances in different operation modes are analyzed and compared with each other qualitatively. The analytical equivalence model of the harmonic impedance is studied, and its accuracy is verified by comparing the calculation results of the analytical method and the test signal method in different operation modes based on the simulation model of an actual HVDC system. Furthermore, the influence of the operation mode on the harmonic impedance is analyzed according to the analytical calculation results, and its conclusion is consistent with the above qualitative analysis. The effect of stray capacitance of the converter transformer casing on harmonic impedance at the inlet of the HVDC transmission line is studied by changing the size of stray capacitance in the converter model, and the equivalence model is simplified.