Frequency response evaluation of state space designed controllers for systems with lightly damped oscillatory modes-A power system stabilizer example

Abstract

This paper concerns the damping controller design of systems with lightly damped modes, such as power systems and large space structures. Four state space pole-placement methods are studied. A frequency response technique shows that to provide the same amount of damping improvement, the space state designed controllers have similar gain and phase at the oscillatory mode frequency, provided no resonance conditions occur. In addition, the frequency response technique can be used to evaluate the impact of the controllers on the stability of unmodeled dynamics and the damping improvement when the system operating condition changes. Insights obtained from such a frequency response analysis are useful for the design of robust controllers. To make the illustrations practical, a power system stabilizer design example is used.