Virtual coupling control of photovoltaic-energy storage power generation system for efficient power support

The key to achieving efficient and rapid frequency support and suppression of power oscillations in power grids, especially with increased penetration of new energy sources, lies in accurately assessing the inertia and damping requirements of the photovoltaic energy storage system and establishing a controllable coupling relationship between the virtual synchronous generator and the main network. In this paper, the inertia and damping requirements of the photovoltaic energy storage system are estimated using frequency safety warnings and power oscillation suppression constraints. Furthermore, the oscillation characteristics of the power system, which include photovoltaic and energy storage in the presence of periodic load disturbances, are analyzed. Based on this analysis, a coupled virtual synchronous controller for energy storage is proposed. This controller employs a forced oscillation suppression technique through natural frequency shifting, and establishes a controllable power coupling relationship between the photovoltaic energy storage system and the main network to achieve the desired frequency shift. Finally, a simulation system incorporating conventional generators and a photovoltaic energy storage system controlled with the proposed strategy is built to test the frequency support and power oscillation suppression behaviors of the grid-connected power generation system.