The sudden change of load has a great influence on the stability of asynchronous generator due to its weakness in loading capacity. Use of static synchronous compensation device（STATCOM）to compensate its reactive power output can enhance the robustness of the system. In this paper

The STATCOM is taken as the study object

the theory of amplitude/phase dynamics is used to establish the transient amplitude phase motion equation model of the device. The transient characteristics of the potential amplitude phase motion of the device during system operation are analyzed

and the shortcomings of the existing control methods are pointed out and improved. It is found by the study that the STATCOM under the traditional voltage stabilizing method only shows the response to the amplitude of the system voltage without responding the voltage frequency of system

namely dynamic. Introduction of frequency control of system under DC voltage scale can keep the STATCOM respond simultaneously voltage amplitude and phase dynamic of asynchronous generator system so to improve stability of the whole system. Both effectiveness and correctness of the control strategy to the system under the multi time scale is verified by the simulation and experimentalresult.