基于Pade近似的广域电力系统关键模态时滞轨迹分析

Time Delay Trajectory Analysis of Critical Modes in Wide-area Power System Based on Pade Approximation

采用广域阻尼控制可有效地提高大型互联系统的动态性能,但广域信号传输带来的时滞对广域电力系统关键模态产生显著影响,从而改变闭环系统稳定性,因此关键模态时滞变化轨迹分析对于广域阻尼控制设计具有重要理论意义。首先采用Pade近似方法将时滞环节转化为状态空间表达式,从而建立考虑时滞环节的电力系统线性化模型;之后建立时滞对电力系统机电模态的影响关系模型;采用Arnoldi特征值计算方法研究时滞对区间振荡模态、局部振荡模态和时滞相关模态的影响规律。以四机两区域系统和New England系统为测试系统,仿真结果表明该方法能够较准确地求解上述模态随时滞变化趋势,从而验证了该方法的有效性。

Wide-area damping control has been suggested to enhance the dynamic performance of interconnected power system.But time delay brought by wide-area signal transmission has a significant impact on the critical modes of wide-area power system,and thus change the stability of closed-loop system.Thus,analysis on time delay variation trajectory of the critical modes is of great theoretical significance for wide-area damping control design to suppress inter-area low-frequency oscillations.Firstly,based on Pade approximation,this paper converts time-delay into state space expression and builds linear model of closed-loop power system including wide-area damping controller.Secondly,the relation model of time delay effect on the electromechanical mode of power system is bulit.Arnoldi method is employed to research the rules of influence of time delay on inter-area oscillation mode,local oscillation mode and time-delay control mode.The method is tested on two-area four-machine system and New England system,and the results illuminate the validity in resolving the influence law of time delay.