Power loop modeling of grid-forming converter and the influence of difference on transient stability

The grid-forming converter （GFM） is prone to transient instability，when a fault occurs in the power grid. At present，the research on voltage ride through control of GFM is comprehensive. However，the influence of power loop difference and interaction on transient stability is rarely analyzed. Therefore，the expression and power-loop model of GFM are derived for transient conditions，based on the typical power-synchronous loops. The expression establishes a bridge to analyze the influence of control loop differentiation. Secondly，the influence of power loop difference on the value of control parameters is analyzed. The difference of active loop is the scaling of control parameters，and the difference of reactive loop is the change of control structure and parameters. Then，the interaction regularity of power loop difference is described. The inertia promotes the coupling of active loop to reactive loop，and voltage correction coefficient alleviates the deterioration of reactive loop to active loop. Finally，the following conclusions are concluded. Increasing damping and decreasing inertia is beneficial to improve power angle and frequency stability，while smaller proportional，integral parameters and larger voltage correction parameters are beneficial to improve voltage stability.