Research On Control Technology Of Inverter Based On Virtual Synchronous Generator Technology

In recent years,with the continuous development of power industry informatization and automation,the application and popularization of power electronic devices have made great progress.To a great extent,the efficiency of energy conversion and use has been improved.However,at the same time,the nonlinear element makes the harmonic pollution in the power system more and more serious,the power quality is obviously affected,which seriously affects the safe and stable operation of the power system.Based on this,it is very necessary to study active power filter which can suppress harmonics dynamically.In this paper,the causes of harmonic generation,harmonic suppression methods and basic concepts in power grid are reviewed.According to the main circuit structure of active power filter and the mathematical model of ABC coordinate system and dq rotation coordinate system,the numerical values of each parameter of the main circuit are determined.Based on the topology of the filter,the simulation model of the harmonic command tracking circuit and the active power filter is built.Secondly,the advantages and disadvantages of the existing harmonic current detection methods are analyzed and compared.Finally,the d-q harmonic command tracking and detecting circuit based on instantaneous reactive power theory is selected to track and detect the harmonic current in the power grid in real time.Then,the current control strategy of the main circuit is designed.This paper reviews the common main circuit control strategies.Firstly,PI control structure is adopted.In view of the low compensation precision of this control strategy,the compensation effect is not ideal.Then the control strategy combining PI and repetitive control is used to simulate the control strategy.Through the analysis of the results,it can be seen that the composite control strategy on the basis of PI control strategy improves the compensation accuracy and speeds up the timeliness of compensation,but it still cannot meet the real-time requirements of the power grid for dynamic compensation.Therefore,a new composite control strategy composed of PI control strategy and sliding mode control strategy is further studied and a new composite controller is designed.The simulation of the new control strategy shows that the new control strategy proposed in this paper improves the compensation accuracy and dynamic response speed.Finally,simulation and result analysis are carried out for the compensation effectiveness of each control strategy in the steady state and dynamic state of the power grid.The compensation capability and response speed of PI and repetitive control strategy in steady state power grid are analyzed.Simulation analysis and result comparison of a new composite control strategy composed of PI and sliding mode control strategy.Then,the compensation effect of the above control methods is considered when the load in the system changes suddenly.The compensation of each control strategy in these two cases is analyzed.Verify the practicability and rationality of the simulation system.