Virtual synchronous generator (VSG) possesses the external characteristics of a voltage source and serves as a crucial supporting device for the safe and stable operation of new-type power systems. This paper establishes an electromechanical transient simulation model of the VSG grid- connected system that takes into account the dual constraints of current limiting and internal electromotive force(EMF) amplitude. For VSG grid-connected systems with different short-circuit ratios

the law is analyzed by which the current limiting constraint causes changes in the equivalent internal EMF amplitude

thereby leading to the migration of the system's oscillation center. In response to the positional characteristics of the oscillation center migration

an active stability control strategy based on VSG states and wide-area branch responses is proposed. For the modified IEEE 10- machine 39-bus system incorporating VSGs

simulations verify the correctness of the oscillation center migration characteristic analysis and the effectiveness of the active stability control strategy in maintaining the stability of the main power grid.