Research On Control Strategy Of Inverter Based On Virtual Synchronous Generator

New energy has the outstanding advantages of environmental friendliness and renewability.Inverter as an important means of new energy access to the grid.How to make the inverter safe,stable and efficient operation,advanced control strategy is essential.Therefore,the research on the control strategy of inverter has become a hotspot at present.The control method of conventional inverter lacks inertia and damping,and the ability to resist external disturbances decreases with the high proportion of grid-connected capacity of new energy.Inverter control strategy based on Virtual Synchronous Generator(VSG)can provide inertia and damping for the system.It is a grid-friendly inverter control strategy and has great significance for its research.Inverter based on VSG control strategy is taken as the research object.The mathematical model of three-phase voltage source inverter is established and its voltage and current double-loop control is analyzed.The working principle of synchronous generator is analyzed.The inverter is controlled by simulating the external characteristics of synchronous generator.The principle of VSG control is researched and the controller is designed.The correctness of VSG controller design is verified by simulation.An improved adaptive control strategy of moment of inertia is proposed.The dynamic phasor model of VSG is built,and the influence of VSG control parameters on system performance is analyzed by small signal analysis method.The influence of moment of inertia on output active power and system frequency is analyzed.When the grid-connected power or load power changes,the improved adaptive control strategy of moment of inertia is proposed to dynamically adjust the moment of inertia according to the change of system frequency and its change rate caused by external disturbances.So this control strategy can improve the stability of the system.The simulation results show that this control strategy is superior to the fixed moment of inertia.A three-phase grid-connected current balance control strategy of VSG based on Multimode High-order Complex Vector Filter(MHO-CVF)is proposed.The influence of unbalanced grid voltage and harmonics on grid-connected current of VSG is analyzed.A multi-module high-order complex vector filter is introduced to extract the positive sequence component of voltage fundamental wave and calculate the given value of grid-connected current to restrain the grid-connected current distortion of VSG output.The correctness of the control strategy is verified by simulation.The experimental platform of three-phase voltage source inverter is designed and built.The main circuit components of the experimental device are selected and the control circuit components are selected.The VSG control strategy,the improved inertia adaptive control strategy of moment of inertia and the three-phase grid-connected current balance control strategy of VSG based on MHO-CVF are verified by experiments.