Large-Signal Stability Analysis of Hybrid Energy Storage System Based on Estimation of Domain of Attraction

The existing research on hybrid energy storage system (HESS) stability mostly focuses on small-signal stability analysis methods. However, when large-signal disturbances occur, the intrinsic nonlinearity of the HESS becomes inevitable so that the small-signal studies are no longer valid, which is beyond the scope of small-signal stability analysis. To address this problem, a large-signal stability analysis method of the HESS is proposed based on the estimation of domain of attraction (DOA). This method can not only analyze the asymptotic stability of the operating point, but also answer the question of how large deviations from the operating point can be tolerated by the system. Specifically, the state space model and Takagi-Sugeno (T-S) fuzzy model of the whole system are first constructed. By using linear matrix inequality (LMI) and Lyapunov's method, the DOA of the system at the operating point is estimated, and the large-signal stability of HESS is analyzed. On this basis, the influence of system parameters (e.g. virtual resistance, virtual inductance and PI regulators) and load power on the large-signal stability are studied, and the dominant parameters affecting the large-signal stability of the HESS is clarified, which provides a practical guiding basis for the parameter optimization design of the HESS to ensure the safe and stable operation of the system under extreme load switching conditions. The simulation results verify the feasibility and effectiveness of the proposed large-signal stability analysis method and the correctness of the analyzing results.