Research On Effect Of Virtual Synchronous Generator On Low Frequency Oscillation Characteristics Of System

In recent years,the proportion of new energy generating units in the power system has increased year by year,but due to the fluctuation and discontinuity of new energy power generation,large-scale new energy access to the grid will pose a certain threat to the stable operation of the grid,and distributed power supplies are connected to the grid through power electronic devices,but the inverter power supply does not have the inertial support of a synchronous generator(SG),which puts a lot of pressure on the frequency modulation of traditional generators.In response to the above problems,a virtual synchronous generator(VSG)control technology is introduced.The VSG is approximately equivalent to a synchronous generator in terms of external characteristics through a certain control strategy.But at the same time,low frequency oscillation is inherented in generators.This article focuses on the analysis of the impact of the VSG at the transmission end of the new energy on the low-frequency oscillation between the system machines,and explores the decisive factors of the VSG influence on the characteristics of the lowfrequency oscillation between the system machines.First,model the various control links of SG and VSG.Then set up two systems of SG-SG and VSG-SG.Observing the movement of the low-frequency characteristic trajectory when changing the inertial time constant and the active frequency modulation coefficient.Analysis of the similarities and differences of the system low-frequency characteristics are conducted.Finally,two factors affecting the low-frequency oscillation characteristics are analyzed: the frequency modulation speed and the virtual impedance.By building the corresponding model on the RT-LAB simulation platform for simulation verification,the simulation results are consistent with the experimental results,indicating that the faster the frequency modulation speed of the VSG,the smaller the virtual impedance,and the more obvious the effect of the VSG on the inter-machine low-frequency oscillation.