Research On Control Strategy Of Micro Grid Inverter Based On Virtual Synchronous Generator

In recent years,with the increasingly serious energy problems faced by the world,new energy power generation technologies such as solar energy and wind energy have been developed rapidly,and distributed power generation has attracted more and more attention.Distributed power generation improves the utilization of energy,but due to the lack of inertial support in the micro grid system,it is not conducive to the stability of the system operation.The Virtual Synchronous Generator(VSG)control technology can simulate the external characteristics of the synchronous generator,increase the inertia of the micro grid system,and thus improve the system stability.This paper takes the working principle and control strategy of VSG as the research object.First,establish the mathematical model of the synchronous generator,establish the mathematical model of the VSG on this basis,and give the specific implementation method of the VSG control algorithm,and then model the implementation carrier of the VSG control algorithm-three-phase full-bridge inverter.The principle of selecting the parameters of related components of the main circuit is given.The voltage and current double-loop control is designed in the two-phase rotating coordinate system and the calculation method of the controller parameters is given.The off-grid/on-grid switching method of VSG is given.In off-grid operation mode,the traditional VSG's constant rotational inertia control strategy can not take into account the impact on the frequency dynamic performance when the load disturbance is generated and eliminated.Adapting to the control strategy,using the flexibility of power electronic device control,by analyzing the power angle characteristic curve of the synchronous generator and its corresponding rotor motion curve,the rotational inertia control principle of the VSG is designed,and its implementation algorithm is given when load disturbance occurs Can guarantee the stability of system operation to the utmost extent.In grid-connected operation mode,for the harmonic suppression of grid-connected current,the output impedance model of VSG is given,the generation mechanism of grid-connected current is analyzed,and a control strategy based on grid voltage feedforward is proposed.The method achieves the purpose of eliminating the influence on grid-connected current by feeding forward the grid voltage on the control structure.Finally,build a simulation model on the MATLAB / Simulink simulation platform to simulate the control strategy mentioned above to verify its correctness and effectiveness.