In order to alleviate the energy pressure caused by the depletion of traditional fossil fuels, new energy sources such as photovoltaics (PV) have been receiving increasing attention and development. However, large-scale PV power plants face practical challenges when connecting to weak electrical grids due to the intermittent nature of energy generation, which is influenced by sunlight intensity. Additionally, these power plants typically connect to the grid through long-distance transmission lines, where line impedance cannot be neglected. Operating large-scale PV power plants in weak grid conditions enhances the coupling with grid-tied PV inverters, often involving components like phase-locked loops and voltage-current controllers. This coupling introduces a series of instability issues characterized by wide-frequency domain and multiple time scales. To ensure the stable operation of large-scale PV power plants when integrated into weak electrical grids, it is essential to understand the mechanisms of oscillatory instability, harmonic amplification, and other related issues. Moreover, appropriate control strategies need to be designed to address these challenges effectively. <div> <div> </div> </div>

photovoltaic power plants,weak power grids,oscillation stability,harmonic resonance,voltage protection