V/f控制MMC带换流变压器空载充电发生高频振荡的机理分析  

High-frequency Oscillation Mechanism Analysis of V/f Controlled Modular Multilevel Converter Charging with Converter Transformer Under No-load Condition

作　　者：李冠群 叶华[1] 宾子君 LI Guanqun;YE Hua;BIN Zijun(School of Electrical Engineering,Shandong University,Jinan 250061,China;Electric Power Research Institute of State Grid Jiangsu Electric Power Co.,Ltd.,Nanjing 211103,China)

机构地区：[1]山东大学电气工程学院,山东省济南市250061 [2]国网江苏省电力有限公司电力科学研究院,江苏省南京市211103

出　　处：《电力系统自动化》2023年第11期50-59,共10页Automation of Electric Power Systems

基　　金：国家自然科学基金资助项目(52077126);泰山学者工程资助项目。

摘　　要：风电经柔性直流输电并网系统中,V/f控制的模块化多电平换流器(MMC)带换流变压器空载充电时可能发生高频振荡,换流变压器动态和MMC控制环节动态对系统高频振荡有较大影响。文中研究V/f控制MMC带换流变压器空载充电发生高频振荡的机理,分析交流电路参数和MMC控制参数对系统高频小干扰稳定性的影响。首先,建立考虑换流变压器杂散电容的送端MMC换流站谐波状态空间模型,通过分析换流变压器杂散电容变化时的特征值轨迹,并与时域仿真结果进行对比,说明高频小干扰稳定性分析中考虑杂散电容的必要性。然后,对MMC带换流变压器空载充电时的高频振荡模式进行参与因子分析,确定参与程度较高的状态变量和关键环节,建立适用于高频小干扰稳定性分析的降阶模型,并利用阻抗特性分析揭示系统发生高频振荡的机理。最后,通过计算系统特征值轨迹,分析交流电路参数和MMC控制参数对系统高频小干扰稳定性的影响,利用电磁暂态仿真验证了分析结果的正确性。In the flexible DC transmission system for wind farm integration,high-frequency oscillation may occur when V/f controlled modular multilevel converter(MMC)charges with the converter transformer under the no-load condition.The dynamics of the converter transformer and the MMC control links have significant influences on the high-frequency oscillation of the system.This paper studies the high-frequency oscillation mechanism when V/f controlled MMC charges with the converter transformer under the no-load condition,and analyzes the influences of parameters of the AC circuit and MMC control on the high-frequency small-signal stability of the system.First,the harmonic state space(HSS)model of a sending-end MMC station considering converter transformer stray capacitance is established.By analyzing the eigenvalue locus with varying converter transformer stray capacitance and comparing it with the time-domain simulation results,the necessity to consider the stray capacitance in the highfrequency small-signal stability analysis is revealed.Then,the participation factor analysis is carried out for the high-frequency oscillation modes when MMC charges with the converter transformer under the no-load condition.The state variables with highdegree participation and corresponding key links are determined.A reduced-order model suitable for the high-frequency small-signal stability analysis is also established.Besides,the mechanism of the high-frequency oscillation is revealed by the impedance characteristic analysis.Finally,the influences of parameters of the AC circuit and MMC control on the high-frequency small-signal stability are analyzed by calculating the eigenvalue locus of the system.The analysis results are validated by the electromagnetic transient simulation.

关 键 词：柔性直流输电 高频振荡 模块化多电平换流器 稳定性分析 谐波状态空间 特征值分析 阻抗分析 

分 类 号：TM721.1[电气工程—电力系统及自动化] TM41