计及电压测量特性的MMC中高频阻抗建模及稳定性分析

Medium-High Frequency Impedance Modeling of MMC and System Stability Analysis Considering Voltage Measurement Characteristics

在建立MMC阻抗模型时,现有研究未计及电容式电压互感器(CVT)测量特性对MMC阻抗中、高频段的影响,可能会降低柔性直流输电系统稳定性分析的准确度。以渝鄂柔直工程南通道单元为研究对象,在分析杂散电容对500 kV速饱和型CVT测量特性影响的基础上,基于多谐波线性化原理提出了一种计及CVT宽频测量特性的MMC阻抗模型建立方法。采用阻抗分析法分析当柔直换流站接入不同交流系统、运行于不同稳态工作点时,CVT宽频测量特性对柔直系统稳定性的影响。分析结果表明,在某些场景下CVT宽频测量特性将导致系统的振荡频率发生变化。通过电磁暂态时域仿真,验证了所提出的计及CVT宽频测量特性的MMC阻抗模型可提高柔直系统稳定性分析的准确度。

In MMC impedance modelling,the existing research does not take into account the influence of the capacitive voltage transformer(CVT)measurement characteristics on the mid and high frequency bands of the MMC impedance,which may reduce the accuracy of the stability analysis of the flexible HVDC transmission system.By taking the south channel unit of the Yu’E flexible HVDC project as the research object,and based on an analysis of the influence of stray capacitance on the measurement characteristics of a 500kV fast saturated CVT,a MMC impedance modelling method is proposed using the multi-harmonic linearization method.The impedance analysis method is used to analyze the influence of the CVT broadband measurement characteristics on the stability of the HVDC system when the MMC station is connected to different AC systems and operates at different steady-state operating points.The results show that the CVT broadband measurement characteristics will cause the oscillation frequency of the system to change under certain working conditions.Through PSCAD/EMTTDC simulation,it is verified that the proposed MMC impedance model,which takes into account the CVT broadband measurement characteristics,can improve the accuracy of the stability analysis of the flexible HVDC system.