Research On Low Frequency Oscillation Of Power System With Virtual Synchronous Generator

In recent years,the proportion of new energy in the power system has gradually increased,but due to the randomness,volatility and intermittency of its output,it has a certain impact on the stability of the external grid during the process of grid connection.Most new energy sources must be integrated into the grid through inverter devices,Compared with synchronous generators(SG),these power electronic devices do not have large inertia and Advantages such as large damping.In response to this problem,virtual synchronous generator(VSG)technology is applied to power system control.Through the appropriate VSG control algorithm,the new energy power supply is equivalent to a synchronous generator in terms of external characteristics.Based on the analysis of the control principle and mathematical model of the VSG,the paper designs a parameter adaptive VSG control.According to the VSG linearization model,the parameter value range is obtained.Within the value range,the moment of inertia and damping coefficient are based on the system The state adapts to change,so that the system quickly enters a stable state.The VSG model was built in DIg SILENT and connected to the single-machine infinity system and the4-machine 2-area system respectively to verify the effect of VSG adaptive control.Then,taking the single-machine infinite bus system with VSG as the research object,based on the VSG control subsystem and the synchronous generator subsystem model,the Phillips-Heffron model of the interconnected system is established,and the damping torque theory is used to analyze the VSG provid ed to the traditional generator electromechanical oscillation ring.Damping torque,analyze the influence mechanism and effect of VSG on the oscillation stability of the power system,and verify it through calculation examples.Finally,with the help of Active Disturbance Rejection Control(ADRC)that does not depend on the controlled object model,is robust and easy to implement,an ADRC-based VSG additional damping control is proposed to improve the stability of the system.First,the relative unit angular velocity difference is used as the input signal of ADRC.The output signal of the ADRC controller is superimposed on the reference power part of the VSG rotor motion equation.The feasibility of the control strategy is analyzed through linearization and damping torque theory,and the proposed control is verified by simulation.The effectiveness of the strategy.