Pre-synchronization method of virtual synchronous generator based on virtual power

The distributed power generation system simulating the characteristics of synchronous generators is grid-friendly to the large power grid. However, a large dash current may be generated at the instant the virtual synchronous generator (VSG) is connected to the grid. This paper proposes a pre-synchronization unit based on the virtual power and the secondary frequency and voltage regulation to achieve seamless transform between the off-disconnection and grid-connection of VSG. Accordingly, the influence of inertia, damping and droop coefficients on the frequency regulation characteristics is analyzed in detail. Simulation and experimental results show that the proposed pre-synchronization control is able to achieve seamless transform between different VSG modes, which is simpler than the conventional pre-synchronization control, while having a good active and reactive power tracking performance.