A STABLE OPERATION REGION WITH NO LIMIT CYCLES USING THE METHOD OF DOMAINS SEPERATION

In determining the region of stable operation in the plane of two parameters, the issue of limit cycles need be studied carefully. The resonance problem will be raised if the mechanical resonance frequency of power systems'is equal to the limit cycle frequency. Despite the stability of each point in the stable region, it is crucial to determine the boundaries in which one can choose the Automatic voltage Regulator (AVR) parameters in such a way that the global stability with no limit cycle is guaranteed. Seperation of such boundaries to dangrous and safety borders have been investigated in the last few years. Many techniques have been devoted to enhance the safe region such that one can choose the AVR parameters in a better manner. In this paper, the stable region will be separated to a non-limit cycle region and a limit cycle one. The non-limit cycle region is the region in which the adjustable coefficients can be chosen with guarentee that the resonance will never happen. Two different techniques are used here to solve such a problem. Firstly, by scanning of the whole region; secondly by analyzing the describing function. In spite of using the digital computer in both cases, the second technique is much easier and is a time saver than the first one.