According to domestic and international technical standards

grid-forming converters (GFMCs) are required to withstand grid voltage phase angle jumps. However

such disturbances may lead to transient synchronization instability. This paper investigates the transient synchronization stability of multi-parallel grid-forming converters under phase angle jump. First

a synchronization dynamic model is established by drawing analogy with the classical rotor swing equation. Then

to enable quantitative stability assessment

a hybrid method combining numerical integration and the equal area criterion is proposed. By calculating the acceleration and deceleration areas with numerical integration

the proposed method fully considers the effects of damping and the interactions among multiple converters

thus enabling high-accuracy transient synchronization stability assessment with clear physical interpretation. Based on this method

the power feasible region that ensures transient synchronization stability under phase angle jump is further characterized. The influence of active and reactive power control parameters on the power feasible region is also quantitatively analyzed. Finally

the RT-LAB hardware-in-the-loop (HIL) experimental results validate the effectiveness of the theoretical analysis.