In the power system electromagnetic transient(EMT)simulations

the conventional method will produce sustainable numerical oscillations(chatters)when circuit breakers and switches are operated repeatedly. In order to further solve the chatter problems

this paper developes a new high-order algorithm with variable parameters based on the rational approximation of exponential function. This method itself can eliminate chatters

while making up for the shortage of conventional methods by reducing complexity and changing parameters adaptively to improve accuracy and numerical stability. By deriving impedance error coefficients

it has been proved that the simulation accuracy of the proposed algorithm with appropriate parameters is better than conventional methods. At the same time

the algorithm possesses L-stability when appropriate parameters are chosen and its advantages on eliminating chatters are even more prominent. Simulation results show the accuracy and numerical performance of the algorithm

which provides a better solution for off-line/real-time simulations of power systems.This work is supported by National Natural Science Foundation of China(No. 51490683).