Transient stability analysis of the standalone solar‐storage AC supply system based on grid‐forming and grid‐following converters during sudden load variation

Abstract

AbstractThe standalone solar‐storage AC supply system is an efficient form of utilizing renewable energy. The solar‐storage supply system normally includes two types of converters, grid‐forming (GFM) and grid‐following (GFL) converters. Nevertheless, the incompatibility of the dynamic performance between the GFM and GFL converters due to different control schemes may introduce the transient instability risk to the solar‐storage supply system. To address this issue, it is extremely necessary to perform transient stability analysis and stability‐enhanced control for such a system. In this paper, a sixth‐order model of the dc‐link timescale for the solar‐storage supply system is developed, whose accuracy and applicability are verified by comparing with the detailed electromagnetic model. Based on the derived model, the analysis demonstrates that the solar‐storage supply system faces the potential risk of transient instability under large disturbances of sudden load variation, due to the mismatch of the transient response speeds between virtual excitation control of the GFM converter and dc voltage control of the GFL converter. The transient stability boundary of the system is quantitatively investigated, by depicting the basin of attraction of the post‐disturbance equilibrium point. Furthermore, from the perspective of improving the coordination of the transient behaviours between the GFM converter and the GFL converter, the parameters related to virtual excitation control and dc voltage control are designed to enhance the transient stability of the system. Time‐domain simulations and real‐time simulations are conducted to validate the theoretical analysis.DC–AC power convertors, microgrids, power system control, power system transient stability, renewable energy power conversion