Abstract: The phenomenon of numerical simulation oscillation often occurs in the transient stability calculation for large power grid under the condition of extreme voltage and frequency change.It is urgent for automatic identification and adjustment to improve simulation convergence.For this reason,this paper proposes several numerical convergence indices of transient simulation.Based on the ratio of variance and mean of output variables of generators,generator control systems and dynamic load during the integral iteration in the alternating solution process,the key dynamic components affecting the simulation convergence are automatically identified.From the aspects of the iterative initial value improvement,automatic integral step adjustment,rational approximation,and reasonable iterative solution selection,some methods are put forward to improve the dynamic simulation convergence.Finally,the proposed methods are applied in the transient simulation of IEEE 14-bus system and an actual system data,to determine the numerical convergence indices and key dynamic components and automatically adjust the integral step.The results show the correctness and effectiveness of the proposed methods.