Pole-Placement Designs of Power System Stabilizers

This paper examines four pole placement techniques applied to the design of power system stabilizers. These methods are the full state feedback, an output feedback by the projective method [1], a design based on a full order observer, and a low order dynamic compensator also based on the projective method [2]. A single machine infinite bus power system is used to illustrate the different design approaches. The power system stabilizer is designed to provide damping to the local mode of this system. It is shown that in order to provide the same amount of damping improvement, the power system stabilizers designed using the different methods have similar gains and plases at the modal frequency, Figure 1. This result is explained by establishing a link between the frequency modal response method and the close-loop system electromechnical modes. The response of the dynamic controllers with modes close to the local mode is also investigated. It is shown that this situation causes a resonant condition which, in general, should be avoided. This paper also presents a simple robust damping controller design considering two different operating conditions of the power system: a weak connection case and a strong connection case. The robust controller is based on the reduction of two controllers using a Hankel-Norm model reduction algorithm [3].