As the traditional power system undergoes a gradual transition towards a new-type power system with high incorporation of renewable energy sources, the dynamic interaction between these renewable energy sources, weak grid, and LCC-HVDC may potentially give rise to some concerns. The grid-forming energy storage converters are regarded as a crucial component in the construction of a new-type power system, as they possess the capacity to address emerging energy consumption patterns and enhance the rotational inertia of the system. In this paper, we establish an impedance network model of the system in sending AC grid that considers frequency coupling, and derive the system's s-domain node admittance matrix(SNAM). Subsequently, the SNAM method is employed to analyze the oscillation characteristics of the 6-node system encompassing four DFIG wind farms. Combining the participation factor index, the optimal access point for the grid-forming energy storage system is identified as a means of suppressing sub/super-synchronous oscillations and enhancing system stability. Finally, the findings are validated in MATLAB/Simulink.