Transient Stability Analysis of the Grid Forming Inverters Based on Inverse Trajectory Method

With the transformation of global energy structure and the improvement of environmental awareness, grid connected inverters based on grid-forming (GFM) control are receiving increasing attention. However, the transient stability judgment conditions based on traditional equal area criterion (EAC) or Lyapunov method ignore the damping effect, which often leads to significant errors when analyzing the GFM inverters with large damping. This paper uses the inverse trajectory method to characterize the critical stable boundary based on phase diagrams, and intersects with the forward motion trajectory to obtain the critical clearance angle. In addition, the conservatism of the inverse trajectory method is theoretically analyzed, and its conservative boundary is solved. Finally, simulation verification was conducted using the Matlab/Simulink platform, demonstrating the conservatism and accuracy of the proposed method.