Steady-state model of converter for fault analysis in the AC-DC hybrid systems

The conventional fault analysis methods and fault analytical models may not be feasible for the AC-DC hybrid systems because of the highly nonlinear time-varying converters. To solve the problem, the paper presents a mathematical model for the analysis of the performance of HVDC converter during the AC faults, especially asymmetric faults. The model is developed using the improved switching functions. To satisfy the special need of fault analysis, the converter is equivalent to steady-state fundamental impedance. Furthermore, the harmonic characteristics of the converter have been taken into account when asymmetric faults occur. Validation of the proposed model is performed by the calculation results comparing with PSCAD/EMTDC simulation results.