Abstract To address the critical issue of frequency stability in grid-connected photovoltaic energy storage systems, a control strategy based on grid-friendly technologies is proposed. This strategy integrates the principles and topology of traditional Virtual Synchronous Generator (VSG) with adaptive VSG control and pre-synchronization techniques. Firstly, based on the traditional VSG control strategy, the frequency operation curve of the VSG is divided into three intervals corresponding to different control modes: islanding mode, PV-storage frequency stabilization mode, and adaptive regulation mode. Each mode is analysed to understand the impact of different inertia and damping coefficients on system output characteristics. A control strategy that allows for adaptive adjustment of inertia and damping coefficients is designed, referencing the power angle characteristic curve and frequency oscillation curve of a synchronous generator (SG). By introducing inertia elements, the robustness of the system against disturbances is enhanced. Utilizing the operational characteristics of energy storage, the combined PV and energy storage system can better interact with and support the grid. Finally, simulation experiments are conducted by using MATLAB/Simulink. The proposed strategy is compared with traditional adaptive control and VSG control strategies. The results demonstrate that the proposed grid-friendly VSG control strategy offers superior frequency stability, robustness, and response speed.
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