**(3) Differential equation calculation limits**

The numerical ODE solving tool is required to validate the calculated and estimated Floquet multipliers. For time domain simulation, the ODE45 tool of MATLAB was used. In some parameter ranges, the solution diverged within one or two cycles, which means that not enough local minima were gathered to construct the Poincaré surface. In real power system problems, the proposed method is aimed at sustaining oscillation measured by PMU. The computation of solution of Equation (1) is beyond the scope of the present study.
