Application of D-Q frame impedance-based stability criterion in power systems with multiple STATCOMs in proximity

摘要

Impedance-based stability criterion has been proven to be a powerful tool for small-signal stability analysis and design, derived from Nyquist stability criterion and first developed in dc-dc power electronics converter systems. Recently it has been extended to ac systems to address the issues and challenges coming with more and more power electronics based converters connected to the existing ac power grids, either in transmission or distribution level. With that, only terminal information is sufficient to judge small-signal stability, which can be from either impedance model or experimental results. Therefore, internal details of inverters are not necessary, facilitating the system operator to integrate. This paper specifically presents a case study with multiple STATCOMs in IEEE 14-bus system to illustrate the application of the d-q frame impedance-based stability criterion. It shows that the impedance-based stability criterion can predict the small-signal stability with accurate oscillatory frequency for STATCOMs' interactions, and a new instability pattern was found from the impedance point of view.