In order to study the influence of the inverter (Inv) on the stable operation of the "wind-thermal/solar-thermal" bundled sending-end power grid, a control model that takes into account the system parameters and the inertia matching method of different types of power sources are proposed. First, this paper constructs the mathematical model of all the control links of Inv, and then forms the small signal model of the entire research system, which is verified by Matlab simulation. Secondly, based on the small-signal model, the root locus method is used to analyze the influence of system parameters on the internal low-frequency oscillation of the sending-end power grid. The study shows that the shorter the internal line of the sending-end power grid, the larger the resistance-inductance ratio and the more the Inv output, which is more conducive to system stability. Finally, using the principle of equivalent power supply, the inertia matching method of the two types of power sources in the sending-end power grid is derived. The RT-LAB semi-physical simulation verifies that the proposed inertia matching formula can better distribute power and improve the stability of the sending-end power grid. This work is supported by the Science and Technology Project of State Grid Corporation of China (No. 5100-201955014A-0-0-00).