Analytical Calculation of the Grid-Connected Frequency for Energy Storage Power Stations Considering the Influence of the Phase-Locked Loop under Grid Disturbances

Grid-side energy storage power stations provide an effective means to enhance the stability of renewable energy integration into the power grid. Accurate calculation and prediction of key characteristic parameters—such as frequency variation trajectories and maximum frequency deviations—are essential for effective frequency control in energy storage systems and their grid-connected operations. Currently, the power control of such stations primarily relies on Phase-Locked Loop (PLL) technology to track the real-time voltage phase angle at the point of common coupling. However, during grid fault occurrence and clearance, the PLL may exhibit transient responses, leading to phase-locking deviation and consequently reducing the accuracy of frequency prediction. To address this issue, this study proposes a quantitative frequency analysis method for grid-connected energy storage systems that incorporates the impact of PLL dynamics. By examining the propagation path of phase-locking deviation, an analytical model is developed to assess the system’s frequency response and maximum frequency deviation. The accuracy and effectiveness of the proposed method are validated through simulations on a representative test system.