励磁机时间常数对电力系统动态稳定性的影响

励磁机时间常数对电力系统动稳定有显著影响.在高放大倍数的AVR控制下,快速励磁较慢速励磁更容易恶化系统阻尼;但是在同时附加励磁控制的情况下,快速励磁可使系统的机电模式根轨迹远离虚轴,机电模式阻尼较大;而慢速励磁下,系统机电模式根轨迹接近虚轴,机电模式阻尼较小,快速励磁优于慢速励磁.通过对一个8机系统在AVR、AVR PSS和分散协调励磁调节三种控制规律下的特征分析和动态仿真表明:有附加励磁时,快速励磁比慢速励磁更有利于电力系统动态稳定性.最后借助特征向量理论揭示了所得结论的数学本质.

Influence of excitation time constant on dynamic stability of power system

Excitation time constant influences greatly on stability of power systems.According to analysis of roots locus,( )fast excitation tends to decrease damping of power systems which is controlled by AVR than slow excitation.But eigenvalues of power system are far from imaginary axis and strong damping is obtained when fast excitation system is added.On the contrary,eigenvalues of power systems are near imaginary axis and weak damping is obtained when slow excitation system is installed.Eigenvalues analysis and transient simulation results are given based on a 8-machine system which is controlled by AVR,AVR+PSS and decentralized & coordinated excitation law.From the results a conclusion is confirmed that fast excitation is more beneficial than slow excitation for improving dynamic stability of power systems.The mathematics essence is discovered on the basis of eigvalue-eigenvector theory.It is important to realize that fast excitation is characterized by dual effect,it may result in both much stronger dumping and much weaker damping than slow excitation.