Real-time stability analysis of power electronic systems

The paper presents a new method for performing online stability analysis of power electronic systems. The method is based on impedance analysis, where the only information required are measurements taken at a single point. The proposed method injects current composed by several frequencies. The impedance is estimated at these frequencies, and the Vector Fitting method is used to estimate a continuous impedance model. The Nyquist Criterion is then applied to the fitted models of source and load subsystem impedance. The stability analysis is performed continuously with an update rate up to 10 Hz. The proposed method has been compared with the conventional frequency sweep method in an experimental setup.