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

This paper describes how to perform the modal analysis of power system zeros. Based on this, an approach to design and analyze controllers for large scale power systems which supplements conventional methods is proposed. The main idea is to adjust the existing structure of the power 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 under certain signals will increase. This will improve the robustness of the controlled system. Transfer function zeros, how to compute then and the limitations they pose are discussed. A test power system is used for illustrations.