Global nonlinear control with application to power systems

Two nonlinear controllers which are capable of operating over wide ranges are proposed. The required control actions are identified through geometric structural analysis of the (nonlinear) system which helps in exploitation of its qualitative behavior. In the first approach, feedback linearization control is used for increasing the stability margins of the system. In the second approach, the exploitation of the system structural behavior is used for segmentation of its state space. The operating segments are modeled in terms of fuzzy sets and for each region, based on linear or nonlinear control theory approaches, the proper local control law is identified. The global control law is established as the average of local control laws weighted by the operating region membership functions. The approaches are demonstrated for control of a typical power system model as its loading level is varied.