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Previous research indicates that post-fault grid-forming (GFM) converters only work in current limiting control (CLC) mode. However, converters integrating the current saturation algorithm (CSA) can operate in both constant voltage control (CVC) and CLC modes. This paper firstly derives the angle-switched model of the grid-connected system governed by CSA and virtual synchronous generator (VSG). Then, combining the fault and three types of post-fault trajectories, critical clearing angle is analytically formulated through the Segmental Equal Area Criterion (SEAC). Finally, a range of values for the saturated current angle is proposed to ensure that the system is stabilized in CVC mode. Notably, the optimal saturated current angle, which is the minimum value within the range, provides the maximum critical clearing angle. • An angle-switched model for a virtual synchronous generator equipped with the current limit is established. • Segmental equal area criterion is proposed and analytical formulations are derived for the critical clearing angle under three post-fault operational states. • Optimal saturated current angle control is proposed to enhance transient stability by configuring the saturation current angle. [ABSTRACT FROM AUTHOR]