A Passivation Approach to Power Systems Stabilization

Abstract In this paper we address the problem of supression of low frequency oscillations in power systems. These oscillations appear in strongly interconnected networks because of load and topology changes, and they may cause loss of synchronism and generator tripping. We propose the utilisation of passivation techniques to design power system stabilizers for the synchronous generators. The generator to be controlled is described by a standard lagrange model, with three forcing terms: the mechanical torque coming from the turbine, the terminal voltage of the network and the field voltage, which is our control variable. In view of the significant differences between the mechanical and the electrical time scales, the first signal can be treated as a constant disturbance. The terminal voltage may be viewed as the output of an operator, -defined by the remaining part of the network-, which is in feedback interconnection with the generator. Our basic assumption is that the network is always absorbing energy from the generator, whence the interconnection subsystem (as viewed from the generator) is passsive. The control objective is then to close a loop around the field voltage so as to passivize the generator system. We characterize, in terms of a simple linear matrix inequality, a class of linear state-feedback controllers which achieve this objective.