Stability Analysis of Grid-Connected Photovoltaic and Storage Systems under Energy Management

Grid-connected photovoltaic (PV) and storage systems enable coordinated control of PV and energy storage systems(ESS) through energy management, which can substantially improve the economic efficiency of the system. However, systems face oscillations or voltage instability risks due to the converter interactions and dynamic energy management control. To analyze system stability, lots of work has been done focusing on the individual components, such as PV or ESS, which lacks a comprehensive system-level analysis. In addition, the influence of energy management on system stability has not been well analyzed, which makes it difficult to evaluate and improve system stability when energy management control interacts with converters. To address these issues, this paper investigates system stability, taking into consideration the interaction between different converters and energy management control. First, the small-signal impedance model is established for the entire grid-connected PV-ESS system with energy management control, which accounts for the dynamic coupling between energy management parameters and system dynamics. Then, an impedance ratio criterion is derived to assess system stability. And, the influence of system parameters, such as grid impedance, power distribution coefficients, on system stability is analyzed, which can provide a theoretical foundation for further optimization control. Finally, the simulation based on Matlab/Simulink is done to verify the correctness of the theories.