Grid-Forming Photovoltaic-Energy Storage System with Higher Flexibility Based on DC-Link Voltage Synchronization Control

As the grid strength gradually weakens, there is an urgent need to enhance the weak grid adaptability and precise control capability of photovoltaic-energy storage (PV-ES) systems. This paper analyzes the basic principles of the PV-ES virtual synchronous generator (PV-ES VSG) control scheme under the common DC bus. A flexible control scheme for grid-connected PV-ES systems is proposed based on DC-link voltage synchronization control (DVSC). Compared to existing PV-ES VSG control schemes, the proposed scheme can significantly improve the control flexibility of the energy storage and increase the diversity of its control algorithms, while maintaining similar power support capabilities and grid-connected performance. This improvement not only optimizes the performance of the energy storage unit in the power grid, but also reduces its burden and pressure on DC bus voltage control. Simulation results based on MATLAB/Simulink and the experiment results based on the Hardware-In-Loop (HIL) platform validate the effectiveness and rationality of the proposed scheme. The comparison with the PV-ES VSG also shows the advantages of the proposed scheme.