Nonlinear Second-Order Model and Equilibrium Point Characteristic Analysis of DC Traction Power Supply System

Table 1

Relationship between eigenvalue and type of equilibrium point.

Eigenvalues	Type of equilibrium point
𝑝^2−4𝑞>0 and 𝑝>0	Stable node
𝑝^2−4𝑞>0 and 𝑝<0	Unstable node
𝑝^2−4𝑞>0 and 𝑞<0	Saddle
𝑝^2−4𝑞<0 and 𝑝<0	Unstable focus
𝑝^2−4𝑞<0 and 𝑝>0	Stable focus
𝑝=0	Uncertain