Abstract: The power output characteristics of the wind power transmission system are dominated by the wind power converters and their control systems. Under large disturbances, they easily lead to over-limit operation, grid separation, and instability. The transient stability analysis of the wind power transmission system faces challenges. Based on the operation and control principles of wind power converters, this paper analyzes the interaction coupling mechanism among the output power of the wind power transmission system, the depth of voltage sag at the grid connection point, and the DC-side capacitor voltage. An imbalance power-generated impact energy characterization method during fault periods is proposed. Based on this, a transient stability improvement strategy for wind power transmission systems with DC-side capacitor voltage limitation and a supercapacitor capacity configuration method is proposed. Based on simulation examples, the transient characteristics of the wind power transmission system with DC-side capacitor voltage as the state variable are quantitatively analyzed, and the effectiveness of the proposed transient stability improvement strategy for wind power transmission systems is verified through simulation.