电力系统时滞稳定裕度求解方法

Computation of Delay Stability Margin of Electric Power Systems

时滞稳定裕度定义为一个系统在保证小扰动稳定的前提下系统可承受的最大延时值。确定电力系统的时滞稳定裕度对于合理利用相量测量装置/广域测量系统数据、设计广域稳定控制器具有重要意义。文中介绍了一种求解动力系统时滞稳定裕度的有效方法,它首先利用Rekasius变换,将时滞系统的特征方程由一个超越方程变换为普通多项式,并保证在临界特征值处Rekasius变换前后方程完全等效;进一步利用Routh判据确定时滞系统的临界特征值和相应的特征频率;最后借助单机无穷大系统验证了该方法的有效性。计算中发现:当负载和励磁放大系数增大时,单机无穷大系统的时滞稳定裕度会降低;而发电机的阻尼系数对系统时滞稳定裕度的影响则较为复杂,需要进一步加以研究。

There exist delays in the data transferring in power system PMU/WAMS （phasor measurement unit/wide area measurement system）. The estimation of maximum allowed delay time that will not cause the loss of system small signal stability is important in the design of a wide-area measurement based controller. Hence in this paper, the maximum allowed delay time is defined to be the delay stability margin and a method to determine the delay stability margin is proposed. Firstly, the transcendental characteristic equation of the time-delay system is converted into a polynomial equation based on Rekasius transformation. Two equations before and after Rekasius transformation are identical when there is a system eigenvalue on the imaginary axis. Secondly, Routh stability criterion is used to determine the critical eigenvalue, the critical oscillation frequency and the delay stability margin. Finally, a slngle-machine infinite-bus system is used to demonstrate the proposed method. It is found that when the generation output and exciter gain increase, the delay stability margin decreases. While the impact of the generator damping to the delay stability margin is very complicated that needs further studies in future.