Improved control of virtual synchronous generator under unbalance of grid voltage

Asymmetric faults in the power grid will lead to unbalanced grid voltage. When the traditional VSG control operates under unbalanced grid voltage, the output current will be unbalanced, resulting in output power oscillation. This article first establishes a mathematical model for traditional VSG control, and then analyzes the problems that arise when traditional VSG operates under unbalanced voltage in the power grid. The main reason is that there are too many negative sequence components in the system. In response to these issues, this article proposes a positive and negative sequence independent control strategy, which improves the adaptability of VSG under asymmetric faults in the power grid by adding a negative sequence current loop and transient current suppression, and can output different control objectives. The proposed control strategy does not change the VSG characteristics and can operate normally connected to the grid. Finally, the effectiveness of the proposed strategy was verified through MATLAB/simulink simulation.