To solve the problem of how to represent and how to improve the grid-forming ability of GFM converter in very weak grid asymmetric fault scenarios

the characteristic characterization model of VSG under the traditional fault ride-through strategy is firstly deduced and established

which is used to characterize the network synchronization

voltage support and overvoltage suppression characteristics of the inverter during the asymmetric fault stage. Then the concept of grid-forming feasible region of converter during fault stage is proposed

in order to quantitatively measure the severity of grid faults that converter can successfully ride through under different strategies. Secondly

aiming at the problem that the traditional fault traversing strategy may be ineffective in some fault scenarios

this paper proposes an IVC-CAPC type strategy. The simulation results show that

in addition to limiting short circuit current

the srrategy can significantly improve the gird voltage support effect and its own synchronization stability when the grid strength changes.