Impact of Reactive Power Control on Low-Frequency Oscillation of Virtual Synchronous Generators

This letter investigates the impact of typical reactive power control (RPC) on the low-frequency oscillation of virtual synchronous generators, where a unified <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P/\omega$</tex-math></inline-formula> admittance is proposed to indicate the coupling effect resulting from RPC, with clear physical meanings. It is found that the mechanisms of different RPC for affecting oscillation damping are distinct. Specifically, the proportional RPC weakens system damping by reducing synchronization reactance, while inertial and PI-type RPC directly introduce negative conductance. A criterion is then proposed to identify the negative damping caused by inertial and PItype RPC. Finally, the theoretical analysis is validated by simulations.