多端柔直换流站高频谐振及传播机理分析与抑制

doi:10.12204/j.issn.1000-7229.2024.02.003

摘要/Abstract

摘要：

针对空载线路投入引起的多端柔性直流(modular multilevel converter multi-terminal direct current,MMC-MTDC)输电系统高频谐振的问题,首先建立了MMC高频简化阻抗模型,基于阻抗分析法分析了空载线路投入引发单个MMC发生高频谐振的电气机理,分析发现由于空载线路投入使得MMC交流侧等效阻抗在高频段呈现负阻尼,继而引发高频谐振。而后针对不同控制方式下的受端换流站进行联合建模,通过对高频谐振能量在站间的传播路径及其对受端MMC运行影响的研究,发现MMC交流侧高频谐振能通过直流线路对其他MMC产生影响,其影响程度与外环控制方式有关。针对高频谐振问题,采用电压前馈增设带阻滤波器的抑制策略,消除了MMC在高频谐振点的负阻尼,完成了对起振MMC的阻抗重塑,有效抑制了MMC高频谐振,并降低了高频谐振能量传播对其余MMC的负面影响。最后利用RT-LAB5600实时在线仿真平台,验证了MMC高频谐振分析方法的正确性与相应抑制方法的有效性。

关键词: 多端柔性直流(MMC-MTDC), 高频谐振, 阻抗分析法, 能量传播路径

Abstract:

To address the issue of high-frequency resonance in multiterminal flexible direct current (DC) transmission systems caused by unloaded line input, a simplified impedance model is established for MMC in the high-frequency range. Based on the impedance analysis, the electrical mechanism of high-frequency resonance in a single MMC caused by an unloaded line input was analyzed. The analysis shows that owing to the unloaded line input, the MMC AC-side equivalent impedance exhibits negative damping in the high-frequency range, leading to high-frequency resonance. Joint modeling was then conducted for the receiving converter stations under different control methods. By analyzing the propagation path of high-frequency resonance energy between stations and its impact on the operation of receiving MMCs, research has shown that high-frequency resonance on the AC side of MMC can affect other MMCs through DC lines. The degree of the impact is related to the external control method. To solve the problem of high-frequency resonance, a suppression method involving the addition of a bandstop filter to the voltage feedforward was adopted to eliminate the negative damping of the MMC at the high-frequency resonance point, complete the impedance reshaping of the oscillating MMC, effectively suppress the high-frequency resonance of the MMC, and reduce the negative impact of high-frequency resonance energy propagation on other MMCs. Finally, the accuracy of the MMC high-frequency resonance analysis and the effectiveness of the corresponding suppression method were verified using the RT-LAB5600 real-time online simulation platform.

Key words: modular multilevel converter multiterminal direct current (MMC-MTDC), high-frequency resonance, impedance analysis, energy propagation path

中图分类号:

TM71

陈继开, 孙崇博, 李阳, 张嘉扬. 多端柔直换流站高频谐振及传播机理分析与抑制[J]. 电力建设, 2024, 45(2): 26-36.

CHEN Jikai, SUN Chongbo, LI Yang, ZHANG Jiayang. Analysis and Suppression of High-Frequency Resonance and Propagation Mechanism in Multiterminal Flexible Direct Converter Station[J]. ELECTRIC POWER CONSTRUCTION, 2024, 45(2): 26-36.

图/表 17

图1 MMC典型高频谐振现象

Fig.1 Typical high-frequency resonance phenomenon of MMC

图2 四端MMC-MTDC系统仿真模型

Fig.2 Four terminal MMC-MTDC system simulation model

图3 MMC控制器结构框图

Fig.3 Structure block diagram of MMC station controller

图4 MMC高频简化模型

Fig.4 MMC high-frequency simplified model

图5 空载线路投入点等值电路

Fig.5 Equivalent circuit point of unloaded line input

表1 仿真平台主要参数

Table 1 Main parameters of simulation platform

图6 空载线路投入MMC交流侧等效阻抗Bode图

Fig.6 Equivalent impedance Bode diagram of MMC AC side for unloaded line input

图7 下垂站对直流电压站的高频谐振影响框图

Fig.7 Block diagram of high-frequency resonance effect of sag station on DC voltage station

图8 开环传递函数Bode图

Fig.8 Bode diagram of open-loop transfer function

图9 附加带阻滤波器的MMC简化控制模型

Fig.9 MMC simplified control model with additional bandstop filter

图10 带阻滤波器对柔直系统阻抗特性的影响

Fig.10 Influence of bandstop filter on impedance characteristics of flexible DC system

图11 阻抗改善后的MMC交流侧等效阻抗Bode图

Fig.11 Equivalent impedance Bode diagram of MMC AC side after impedance improvement

图12 空载线路投入前后并网点电压电流波形

Fig.12 Voltage and current waveform of PCC before and after unloaded line input

图13 空载线路投入前后仿真波形及FFT

Fig.13 Simulation waveform and FFT before and after the unloaded line input

图14 启用高频谐振策略前后的仿真波形及FFT

Fig.14 Simulation waveform and FFT before and after enabling high-frequency resonance strategy

图15 高频谐振时MMC直流侧电压电流仿真波形

Fig.15 Simulation waveform of voltage and current on the DC side of MMC during high-frequency resonance

表2 各MMC直流侧电压电流波动

Table 2 Voltage and current fluctuations on the DC side of each MMC

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