Abstract
This paper presents a nonlinear dynamic model for a droop-controlled inverter operating in grid -connected mode with local RL loads and phase-locked loop control. The Region of Attraction (ROA) of the nonlinear system in the context of large-signal disturbances is determined using a fast executing modified approach of the LMI based Takagi-Sugeno Algorithm by reducing computational complexity but leading to a more conservative estimate of the ROA. Results for loads of varying R / X ratios show their impact on the size of the estimate of the system's region of attraction. Time domain simulations illustrate the responses to the initial large reactive power disturbance