Stability Analysis and Performance Improvement of Power Sharing Control in Islanded Microgrids

Due to the requirement of synchronism and power sharing, droop control and its variations have become one essential component for distributed generator (DG)-powered microgrids. However, the power sharing accuracy and system stability margin may be threatened by the randomness from the load demand and renewable generation. In this paper, a dynamic stability analysis is first performed on a DG-powered microgrid through a produced system frequency response model (SFR). The results point out that (i) the critical system eigenvalues directly vary with the system operating condition; (ii) a fixed-gain power sharing control is prone to be less damped and loses stability easily under some operating conditions. Then, the heuristic adaptive dynamic programming (HDP) strategy is used for power sharing control with the benefit of adapting to real-time disturbances and uncertainties. Through Lyapunov theorem, stability analysis is provided to demonstrate the reliability of the HDP-based power sharing control in islanded microgrids. Finally, simulation tests verify the analysis results and demonstrate the favorable performance of the HDP-based power sharing control under uncertain load disturbances.