Method of Conjugate Vectors for the Analysis of Single-Phase-to-Ground-Faulted Grid

With the wide application of power electronic devices (PED), the characteristics of the grid fault vary greatly. The grid voltage/current exhibits the time-varying amplitude/frequency characteristics under asymmetrical fault conditions, which have brought new challenges to power system asymmetrical fault analysis. However, the method of symmetrical components based on phasors, which is a traditional method, assumes that the amplitude/frequency of the grid voltage/current remains constant and consequently does not apply to the time-varying amplitude/frequency problem. Hence, this paper proposes a method of conjugate vectors for the dynamic analysis of asymmetrical-faulted grid. The proposed method constructs a forward network, a reverse network, and an impulse network coupled at the fault point by employing rotating vectors. Taking a single-phase ground fault as an example, the dynamic analysis process is introduced. The accuracy of the analysis results is validated with simulation models. It indicates that the proposed method applies to dynamic analysis of asymmetrical-faulted grid under time-varying amplitude/frequency circumstances.