Renewable energy grid connection brings new challenges to the stability of the power system, and it is a feasible solution to adopt motor-generator pair (MGP) for grid-connection method. This paper first introduces the structure of the renewable energy via MGP grid-connected system and its control method. Then the mathematical model of the system is established, and the power transmission model and electromagnetic-mechanical coupling characteristics of the system are analyzed to reveal influence of the control parameters, MGP inertia and damping parameters on system frequency and active power response. The simulation model of renewable energy via MGP grid connection is built in PLECS. In order to analyze the effect of different parameters on the system, by setting voltage faults in the simulation model, and comparing the changes of system frequency and active power. The results show that the optimization of the parameters is beneficial to suppressing and attenuating the oscillations of system frequency and active output. Finally, the frequency and power response are compared at different voltage rising levels in the experiment platform of renewable energy via MGP grid connection. The results show that MGP is helpful to improve the stability of renewable energy grid connection.