Fault Ride-Through Strategy for GFM Inverters Based on Power Command Constraints

[Objective] To address the issues of power angle instability and output current overload in grid-forming（GFM）inverter during symmetrical grid faults，this paper proposes a fault ride-through strategy based on power command constraints. [Methods] First，a transient model of a droop-controlled GFM inverter is established to analyze the transient characteristics of the system under grid voltage sag conditions，revealing the impact of power commands on transient stability. Second，based on the circuit relationship between the inverter and the grid，the characteristics of fault currents and their primary influencing factors are identified. Finally，a fault ride-through method based on active power command constraints is proposed，which only requires calculating and setting the active power command value to restore power angle stability and limit fault currents. [Conclusions] Simulations performed in MATLAB/Simulink demonstrate that the proposed strategy effectively enhances power angle stability，achieving fault ride-through. [Conclusions] The proposed fault ride-through strategy based on power command constraints effectively addresses power angle instability and overcurrent issues in GFM inverters during voltage sag by constraining active power commands，providing a feasible solution for enhancing the fault ride-through capability of renewable energy grid-connected systems.