Conventional electromechanical transient or electromagnetic transient simulators each have their disadvantages and limitations in simulating increasingly large-scale power systems. It is shown that by combining two kinds of simulators to make hybrid simulation

the scale

velocity and precision of calculation can be improved. It also provides a new solution for research on power system transient stability and dynamic characteristics. The key algorithm for dealing with the interface in hybrid simulation is presented in this paper. The solution to equivalent parameter and method of equivalent circuit for two kinds of simulators are discussed. In particular

a new method is presented for solving the equivalent fundamental frequency complex impedance according to the existing post-difference nodal admittance real matrix. In addition

the problem about asymmetric impedance matrix in electromechanical transient simulators and fundamental extraction in electromagnetic transient simulators are also discussed and analyzed at length

providing the specific scheme of implementation and laying a solid theoretical foundation for program design of the hybrid simulation system.