Influence of excitation saturation element on power system voltage stability based on bifurcation theory

With a three-bus power system model, the influences of excitation saturation element and top excitation voltage value on the system voltage stability are studied. Though a smooth function maybe applied to imprecisely simulate the performance of an excitation limiter, a method based on the dimensionality reduction of equation set is adopted, which sets Efd as the top excitation voltage and ignores the excitation transient equations when the excitation saturation element functions. Examples are analyzed by software AUTO 07 and results show that, when the excitation saturation element is considered, the motion trajectory of load bus voltage changes obviously along with the increase of the mechanical input power; when system reaches and runs on the excitation limit, the declining of top excitation voltage makes the load bus voltage more quickly approaching the saddle-node and Hopf bifurcation node along with the increase of mechanical input power, where system is more likely to lose its stability. ©, 2015, Electric Power Automation Equipment Press. All right reserved.