<p>Virtual synchronous generators are not only affected by synchronous resonance but also by the transient stability of the power angle. Although a virtual resistance can effectively suppress synchronous resonance, it will decrease the transient stability of the power angle. In addition, although the increase in the value of inductance of transmission lines connected to the grid will limit fault current, it will further reduce the transient stability of the power angle. To resolve the above contradictions, firstly, the influence of virtual resistance, the inductance of transmission line, and grid voltage sag on the transient stability of power angle are analyzed by the power angle curve and phase portrait in this article. Secondly, by further improving the additional feedback control based on voltage deviation and frequency deviation, the design of control parameters and the adjustment of active power reference during grid voltage sag are made more effective and reasonable while ensuring transient stability of the power angle. Finally, the control strategy of transient stability of the power angle is verified by the simulation results.</p>