Application of modal analysis of zeros to power systems control and stability

This paper describes how to perform modal analysis of system zeros. Based on this, an approach to design and analyze controllers for large scale systems, e.g, power systems, which supplements conventional methods is proposed. The main idea is to adjust the existing structure of the system by retuning internal control loops to relocate critical zeros, thus removing the constraints that arise when zeros are at unsuitable locations; the small-signal dynamics of the power system will be more controllable with a particular device, and even its observability in certain signals will increase. This will improve robustness of the controlled system. Transfer function zeros, how to compute them and the limitations they pose are discussed. A test power system is used for illustrations. (C) 1998 Elsevier Science S.A. All rights reserved.