The virtual synchronous generator(VSG)realizes the virtual inertia control of the converter by simulating the swing equation of traditional synchronous generator

which also suffers the transient instability under large disturbance. This paper analyzes the transient stability of the VSG connected to the infinite bus. Firstly

the large signal model of the inverter controlled by the VSG is established and the system order is reduced based on the singular perturbation theory. The correctness of the model is verified by comparison with the electromagnetic transient simulation model. On this basis

the cell mapping method is introduced to analyze the global nonlinear characteristics of the reduced order model. The region of attraction in the phase plane

which is represented by the virtual angular velocity and the virtual phase angle is found and the key factors that affect the stability of the VSG under large disturbance are analyzed. The results of the analysis are compared with the results of the small signal analysis

which shows that system parameters

such as the internal impedance of the power grid

the feeding power

the virtual inertia

the damping coefficient and the filter parameters

have significant influences on the transient stability of the VSG under large disturbance. Finally

based on MATLAB/Simulink simulation

the rationality of the proposed method is verified.