不对称故障下构网变流器故障电流解析计算OA

To addresses the challenge that the fault current of grid-forming converters is strongly affected by the cou-pling between control strategies and electromagnetic transients,which causes difficulty in analytical calculation,an an-alytical calculation method for the fault current of grid-forming converters under asymmetric faults is proposed in this pa-per.First,based on the differences in dynamic response speed among the converter's control loops,the mathematical model of fault current is simplified into a fast-slow timescale separation model composed of reactive power-voltage con-trol loop dynamics and fault current dynamics.Then,an analytical expression for internal potential is derived according to the reactive power-voltage control loop,which is further substituted into the positive-sequence component dynamic equation of fault current.The negative-sequence component is subsequently superimposed to yield an analytical expres-sion for the fault current of the grid-forming converter.Compared with the conventional numerical or approximate model-ing methods,the proposed approach can accurately characterize the transient current characteristics of grid-forming con-verters under asymmetric faults,so as to reveal the coupled effects of control parameters,virtual impedance and grid conditions on the amplitude and phase of fault current.The results in this paper provide a theoretical foundation for the design of fault current-limiting strategies and the optimization of engineering parameters.