输电线路两端受控电压源失谐引发功率振荡的机理分析  

Mechanism Analysis of Power Oscillation Caused by Disharmony of Voltage Source Controlled-units at Both Sides of Transmission Line

作　　者：于其宜 汤奕[1] YU Qiyi;TANG Yi(School of Electrical Engineering,Southeast University,Nanjing 210096,Jiangsu Province,China)

机构地区：[1]东南大学电气工程学院,江苏省南京市210096

出　　处：《中国电机工程学报》2024年第15期5908-5920,I0006,共14页Proceedings of the CSEE

摘　　要：随着构网型(grid-forming,GFM)变流器技术的成熟以及在维持弱电网稳定性方面的优势,其将广泛应用于新型电力系统中的柔直、储能等并网单元。受分布式GFM变流器频率测量和控制精度差异及电网频率时空分布特性的影响,易发生交流输电线路两端基于GFM型变流器的电压源型受控单元(voltage source controlled-unit,VSCU)输出频率长时间不一致的失谐现象。失谐是否会进一步引发线路异常的功率振荡问题,亟待研究。首先,该文基于GFM型变流器不同控制策略特点以及引发失谐诱因的分析,建立输电线路两端带失谐VSCU的等效电路模型;其次,从拓展新型电力系统稳态潮流研究的角度,推导线路单相瞬时电流和单相瞬时功率在失谐VSCU作用下的计算式,并定义反映失谐前后瞬时电流和瞬时功率振荡峰值倍增效应的峰值放大系数;最后,从VSCU间同步和同谐能力两方面,指出峰值放大系数和最大峰值出现时间受线路长度、失谐程度和初相位差影响的变化规律,并拓展分析频率测量精度对失谐型振荡的影响。研究表明,仅通过提高GFM型VSCU间的自同步能力或GFM型控制策略精度/频率测量精度无法从根本上解决失谐型功率振荡问题。As the technology of grid-forming(GFM)converters matures,offering advantages in maintaining stability of weak network,these converters will be widely applied to grid-connected units connected to new power system,such as flexible direct current transmission system and energy storage.Due to the difference in performance of GFM converters’strategy under distributed control,frequency measurement accuracy at each node,and spatiotemporal distribution characteristics of frequency,the long-time different output frequency between voltage source controlled-units(VSCUs)at both sides of AC transmission line will easily cause disharmony under normal operation.It is urgent to study whether such disharmony will further cause abnormal power oscillation.First,based on the analysis of different control strategies of GFM converters and influence factors of disharmony,an equivalent circuit model of an AC transmission line with disharmonious VSCUs is established.Then,to extend power flow analysis of new power systems,the formulas of the single-phase instantaneous current and power of the transmission line under disharmony conditions are deduced.The current and power peak gains are defined to measure the peak amplification effect of oscillation before and after disharmony.Finally,from the two aspects of synchronization capacity and harmony ability between VSCUs,the effects of line length,disharmony degree,and initial phase difference on the peak gain and the first appearance time of the maximum peak are analyzed.Furthermore,the influence of improving frequency measurement accuracy on disharmony oscillation is discussed.The results show that the disharmony oscillation cannot be eliminated only by improving self-synchronization capability between the GFM VSCUs,or GFM control accuracy,or frequency measurement accuracy.

关 键 词：新型电力系统 失谐 功率振荡 构网型变流器 电压源型受控单元 分布式控制 

分 类 号：TM75[电气工程—电力系统及自动化]