When the wind farm is connected to the power system, certain issues, such as SSO, will be caused, rendering the protection of the power grid unstable. Researchers have found that this situation can be effectively avoided by direct-drive permanent magnet wind power generation. Generates synchronous frequency oscillation is with the help of a grid connection without series compensation. This mode of power generation is part of a new method of subsynchronous oscillation of the wind farm, and the concepts and steps are not explicit. From the point of view of theory, this paper analyzes the causes of its effect, as well as the methods and measures used, and lists the study reports and findings on the synchronous oscillation of grid-connected direct-driven wind farms at home and abroad. At the end of the article, the author also put forward the hypothesis and the imagination of this process. The theory of the wind fire bundling DC transmission system is that the equipment and AC current will communicate, and synchronous electrical oscillation will also occur, and the torsional vibration of the thermal power unit will occur. Our study starts from the investigation of the and explaining the theory behind the wind power and AC network. In combination with the power grid parameter data, the oscillation times of subsynchronous current harmonics in the wind farm are obtained in a specific environment and the conditions of the subsynchronous harmonic generation are analyzed. At the same time, the effect of line harmonic impedance and current oscillation frequency is also simulated.