Power Reserve for Grid-Forming PV Sources with Stability Enhancement in Mixed-Source Microgrids

Abstract

Mixed-source microgrids that include grid-forming photovoltaic (PV) microsources and synchronous generators suffer from high vulnerability to survivability challenges. The drop in system frequency, current overshoots, and PV dc bus voltage sag can be severe during PV dynamic overloading conditions. Control strategies to enhance the power reserve capabilities of grid-forming PV microsources are presented in this paper. The proposed strategies improve the microgrid's transient dynamics, strengthening the frequency and PV de bus voltage regulation characteristics in mixed-source microgrids under high-load conditions. Two versions of the power reserve control strategies are presented. Simulation results are provided that demonstrate the effectiveness of both proposed strategies. Performance comparisons of the two strategies are provided that highlight differences in their abilities to autonomously retain the same reserve margins following load changes.