Large signal stability analysis based on gyrator model with constant power load

Power electronic converters are widely used in advanced automobiles, especially in electrical vehicles (EVs). However, the stability analysis of the advanced automotive electrical systems which composed by multi-voltage level hybrid ac and dc systems is much complex than a single converter. In the system level, the downstream converter behaves as a constant power load (CPL) which shows negative incremental resistance and may cause negative impedance instability in the system. In addition, there is no general model for large signal stability analysis of nonlinear dynamical systems. In view of the above, this paper set up a reduced order large signal model for the step-down cascaded system first, and analyzes the stability of converters with CPL based on Lyapunov stability theory. Phase plane analysis and attraction region are presented to demonstrate the system stability. Key parameters are also analyzed in detail. The simulation results using Saber software confirm the theoretical analysis.