Admittance-Based Stability Analysis: Bode Plots, Nyquist Diagrams or Eigenvalue Analysis?

In the literature, Bode plots and Nyquist diagrams are used extensively in stability analysis for admittance-based models. In this letter, we demonstrate that eigenvalues obtained from the total admittance lead to accurate prediction of stability while Bode plots and Nyquist diagrams show limitations. A voltage source converter with weak grid interconnection is used as an illustrative example to demonstrate the pros and cons of the three methods applied to dq-frame admittance matrices.