针对间隙非线性环节的水轮机调节系统稳定性分析

An analysis on stability of hydropower systems with backlash nonlinearity

间隙环节是机械系统中典型的非线性环节,亦存在于水轮机调节系统中;随着水轮发电机组服役年限的增加和执行机构的老化,间隙特性的影响也愈加明显。推导了孤网运行工况下水轮机调节系统各部分的传递函数,运用描述函数法表示系统执行机构内的间隙特性,建立了具有间隙非线性环节的水轮发电机组模型。通过理论分析,基于Nyquist稳定判据分析了间隙特性对系统稳定性特征的影响,并采用时域数值仿真,模拟了在频率调节模式下负荷扰动的小波动过渡过程。结果表明:间隙特性能使机组瞬态性能恶化,甚至使系统产生极限环振荡,系统稳定性特征受到间隙死区大小、间隙特性与调速器参数匹配规律等因素的影响。分析结果可为具有典型间隙非线性环节的水轮机调节系统小波动稳定运行提供理论支持。

Backlash is a typical nonlinearity in mechanical systems,and it also exists in hydropower systems.With the increase of the service age of hydro-generators and the aging of actuators,the influence of backlash is more and more obvious and important.In this paper,the transfer functions of the islanded hydro-turbine governing system are derived,the backlash in the actuator of the system is expressed by the description function method,and the model of the hydro-generator with backlash nonlinearity is established.The influence of backlash on system stability characteristics is analyzed based on Nyquist stability criterion by theoretical analysis,and the transition processes of small load disturbance in frequency regulation mode are simulated by time domain numerical simulation.The results show that backlash deteriorates the transient performance of the system,and even induces the limit cycle oscillation,and the stability characteristics are affected by the size of backlash,the matching law of the backlash characteristics and the parameters of the governor as well as other factors.The analysis results provide theoretical supports for the small fluctuation and stable operation of hydropower systems with typical backlash nonlinearity.