Restraining Method of Subsynchronous Oscillation in Virtual Synchronous Generator Based on Impedance Reshaping

Virtual synchronous generator (VSG) simulates the rotor motion equation to enable power electronic devices to have the inertia and damping characteristics of synchronous generators. However, subsynchronous oscillation is prone to occur when the VSG is connected to the series capacitor compensation power grid. In response to this issue, this article first establishes a sequence impedance model of VSG and series capacitor compensation power grid. Then, the mechanism of subsynchronous oscillation is analyzed using the Bode diagram, and the limitations of traditional active damping methods are studied. On this basis, a restraining method of subsynchronous oscillation in VSG based on impedance reshaping is proposed. An impedance reshaping controller is added to the feedback loop of the VSG damping coefficient, and the impedance characteristics of the proposed system are analyzed using the Bode diagram.This impedance reshaping method can reduce the impedance phase difference between the VSG and the series capacitor compensation power grid in the low frequency range, effectively suppressing the occurrence of subsynchronous oscillation. Compared to traditional active damping control methods, the proposed subsynchronous oscillation suppression method can better adapt to changes in system operation mode and will not cause the virtual synchronous generator working point to shift. Finally, the effectiveness of the proposed method is verified through simulation and experiments. ©2024 Chin.Soc.for Elec.Eng.