To investigate the evolution trend of transient stability of power-controlled grid-forming(GFM)converters connected to AC systems,generators are replaced with power-controlled grid-forming(GFM)converters and grid-following(GFL)converters of equal capacity using the IEEE 39-bus AC test system.Additionally,the number of connections and integration positions in the AC system are varied for electromagnetic transient simulations.The re-sults indicate that power-controlled grid-forming converters exhibit superior transient stability enhancement capabili-ties in the integration area,especially when the replaced generators are adjacent.As the proportion of such convert-ers in the system increases,the system's transient stability strengthens.Furthermore,higher equivalent inertia coef-ficients within power-controlled GFM converters lead to weaker synchronous stability of the system,whereas higher internal damping coefficients enhance synchronous stability.