Asymmetrical fault analysis on distribution feeders with inverter interfaced distributed generators

Abstract

As the penetration level of the inverter interfaced distributed generators (IIDGs) increases, it is necessary to consider the effect of the IIDG connection on fault analysis in distribution networks. To extend the conventional analysis methods, this paper proposed a sequence component-based method to analyse the asymmetrical short-circuit faults. The boundary condition alternation caused by the IIDG connection was presented as well as its effect on the phase components of the feeder fault currents. Moreover, the difference between fault currents before and after IIDG connection was analysed, considering the boundary condition alternation. The fault current values obtained in network without IIDG connection were used to calculate fault currents of the feeders connected with IIDGs, which can simplify the calculation process and reduce the calculation time. The proposed method was programmed and implemented on different cases, and results were compared with the simulation and conventional analysis method. Comparisons demonstrated the improvements of the proposed method in accuracy of the results and calculation time. The new method can be conveniently integrated into software packages for power system analysis and relay protection evaluation.