A Fast Method to Identify the Order of Frequency-Dependent Network Equivalents

Rational approximation of frequency-dependent network equivalents with vector fitting (VF) is widely used in power system analysis; however, a detailed examination of methods to determine the order of the model has not been reported. The traditional order identification method of the frequency response resonance peak is conservative, as demonstrated in this paper. We discuss the essential relationships between VF and Prony analysis (PA). A PA-based method is then proposed to identify the order of model, considering the resonance peaks. The method is computationally inexpensive, and the precision can be adjusted easily. Numerical investigations demonstrate the validity and efficiency of the method.