构网型变换器故障恢复阶段电流越限机理及安全控制研究OA

Virtual impedance technology effectively prevents overcurrent in grid-forming converters during faults,but during the fault recovery stage,there's a risk of current exceeding limits.This paper analyses this post-fault overcurrent mechanism and discovers that the converter's overcurrent occurs only if the virtual impedance design value is higher than the grid's impedance value.Under this condition,the increasing of virtual power angle is the main cause of overcurrent.Accordingly,this paper proposes a current safety control strategy that dynamically adjusts virtual impedance and power command values.This strategy restrains the output current within the safe range while ensuring transient power angle stability.Simulations and experiments confirm the correctness of theory and the effectiveness of proposed strategy.