The Overcurrent Limiting Method of GF-SVG in a Wind Farm Based on Adaptive Virtual Reactance

As a new dynamic reactive power compensator, the grid-forming Static Var Generator (GF-SVG) can not only provide reactive power-voltage support, but also has inertial support capability. It has been experimentally deployed in many wind farms. However, studies have shown that when the three-phase short-circuit fault occurs in the wind farm, the transient overcurrent during the fault occurrence and fault clearance is suppressed, making it difficult for GF-SVG to use traditional fixed virtual impedance. Aiming at the problem, firstly, the influence of virtual reactance on control stability is analyzed using the GF-SVG’s current open-loop transfer function. Secondly, based on the existing current limitation strategies of GF-SVG, an adaptive virtual reactance current limitation strategy suitable for symmetrical faults of the power grid is proposed, which limits GF-SVG’s transient overcurrent during fault occurrence and fault clearance stage to the tolerance range of GF-SVG’s power devices. Based on the GF-SVG’s active power loop and reactive power loop small signal models, the availability of the proposed adaptive virtual reactance in suppressing the DC voltage drop of GF-SVG is analyzed, and shortening the transient overvoltage recovery time of the wind farm after the fault clearance is also discussed. Finally, electromagnetic simulation proves the effectiveness and correctness of the proposed adaptive current limitation method.