调速死区和限幅参与的火电机组超低频频率振荡及近似分析

Ultra-low Frequency Oscillation Engaged with Governor Dead Zone and Limit in Thermal Power Unit and Its Approximation Analysis

水电系统中多次出现与调速死区和限幅相关的超低频频率振荡现象,而火电系统中是否存在类似风险有待研究。首先建立了考虑死区和限幅的单机火电非光滑动力系统模型,然后分析了参数变化时火电系统的平衡点、调节区域阻尼特性以及超低频频率振荡风险,并结合描述函数法近似分析了非光滑振荡特性。结果表明,正阻尼时单机火电系统存在死区和限幅参与的超低频频率振荡现象,其与传统光滑系统负阻尼下的振荡不同,无法用平衡点特征根进行分析,但可采用描述函数法近似分析其振荡频率和幅值特性。

The phenomenon of ultra-low frequency oscillation related to the governor dead zone and limit has occurred many times in hydropower systems,and whether there is a similar risk in the thermal power system is still a problem to be investigated.In this paper,the non-smooth dynamic system model of a single-machine thermal power system consid⁃ering the governor dead zone and limit is established.The equilibrium point,damping characteristics of regulating re⁃gion,and risk of ultra-low frequency oscillation of the thermal power system are analyzed when the parameters change.In addition,combined with the description function method,the non-smooth oscillation characteristics are approximate⁃ly analyzed.Results show that the phenomenon of ultra-low frequency oscillation engaged with the governor dead zone and limit exists in the single-machine thermal power system with positive damping,which is different from the oscilla⁃tion of the traditional smooth system with negative damping and cannot be analyzed by the eigenvalue analysis.Howev⁃er,the corresponding frequency and amplitude characteristics of oscillation can be analyzed by the description function method.