风电并网系统次同步振荡建模与分析

Modeling and Analysis of Sub-Synchronous Oscillation in Wind Power Grid Connection System

随着风电串补技术在国内的大量应用,也暴露出其存在的安全问题。河北沽源、新疆哈密等地均发生多起次同步振荡事件,导致系统无法安全稳定运行。针对双馈感应风机(double fed induction generator,DFIG)经串联补偿线路外送功率引起的次同步振荡(sub-synchronous oscillation,SSO)问题,建立数学模型;并基于PSCAD搭建仿真模型,分析风电并网系统的SSO影响因素。通过分析可知:风速越小,串补度越高,就越容易发生次同步振荡;在串补度越高的情况下,次同步振荡频率越大,电气阻尼系数越低;转子侧变换器电流内环的比例系数和积分系数越大,产生的次同步控制互作用(sub-synchronous control interaction,SSCI)就越剧烈,对次同步振荡产生影响越大。

With the extensive application of wind power series compensation technology in China,it also exposes the existing safety problems.There are many sub-synchronous oscillation(SSO)events in places such as Guyuan in Hebei and Hami in Xinjiang,which lead to the system can not operating safely and stably.In this paper,a mathematical model is established to solve the SSO problem caused by the outputting power of double fed induction generator(DFIG)through a series compensation line,and the simulation model based on PSCAD is built to analyze the influencing factors of SSO in wind power grid connection system.The analysis shows that,the smaller the wind speed is,the higher the degree of series compensation is,the easier the sub-synchronous oscillation is;when the degree of series compensation is high,the higher the frequency of sub-synchronous oscillation is,the lower the electrical damping coefficient is.The larger the ratio coefficient and integral coefficient of the current inner loop of the rotor-side converter is,the more intense the sub-synchronous control interaction(SSCI)will be and the greater the influence on the SSO will be.