Region of Attraction Estimation for Large-Scale DC Microgrids With Low Computations

Due to high energy efficiency and low energy losses, DC microgrid is a promising solution for integrating renewable energy source. Nevertheless, the system may suffer instability when subjected to large disturbances including abrupt load changes and line fault. The region of attraction (ROA) is an important indicator for measuring the large-signal stability in a system, which ensures the convergence of the system state trajectory after large disturbances. However, the issue that estimating the ROA for DC microgrids, especially for large-scale DC microgrids, has not been resolved completely. This paper mainly focuses on the estimation of the ROA of DC microgrids with constant power loads (CPLs). Firstly, the Lyapunov energy function of meshed DC microgrids based on Brayton-Moser's mixed potential theory is calculated. Secondly, we propose a framework of estimating the ROA of high-voltage equilibrium for DC microgrids using Brayton-Moser's general mixed potential function (GMPF), which provides useful perspectives for designing algorithm of estimation of ROA. Thirdly, an analytical energy function value is developed, which reduces computations greatly. Compared to existing results, the proposed critical energy function value is greater. Finally, simulation results verify the feasibility of the proposed method.