With the development of a high proportion of new energy grid connection, the resonance of new energy grid connection systems has become a potential factor affecting the safety and stability of new power systems. Because of the complementary characteristics of wind and solar resources in the time scale, the time-sharing and mutual aid of system damping can be realized by adjusting the grid-connected characteristics of the inverter. Aiming at the parameter design problem of the inverter impedance adaptation branch, an optimal design method is proposed. First, the output impedance expression of the inverter with damping complementary control is derived, and the influence of the damping coefficient on the output impedance is analyzed by combining the amplitude and phase of impedance, and the primary design method of the damping coefficient is proposed. Subsequently, the relationship between the impedance of the power grid and the damping coefficient is analyzed from the perspective of system stability, providing a basis for optimizing the damping coefficient. To address the limitation of fixed damping on control, a damping coefficient adaptive damping complementary control is proposed, making the control more flexible and effective. Finally, the accuracy of the impedance adaptation branch parameter design method and the effectiveness of the damping coefficient adaptive algorithm are verified through simulation and experiments.