Characteristics of Symmetrical Components During Unsymmetrical Faults in Distribution Network with PV-Inverter Connected

Abstract

This work modelling the 13 nodes IEEE test feeder connected to a PV-Inverter Single phase to ground (LG) fault and phase to phase (LL) fault are performed to observe the characteristics of the current symmetrical components for pre fault and steady state post fault. Modifications were made to the system under study, where the system is modeled as a source, line, and transformer impedance only. Other parameters were ignored because the aim of this work was to study short circuit faults. The 3 phase PV-inverter is modeled as a second-order generalized integrator (SOGI) frequencylocked-loop (FLL) representation. This model replaces the inverter model as an ideal current source and its positive sequence current, which cannot provide an exact picture of the symmetrical component of the current when an unsymmetrical short circuit fault occurs. The system model was developed using ATP/EMTP. The (LG Fault) simulation results show that the contribution of the fault current and positive sequence current from the PV-Inverter does not experience a significant increase. The same thing also happens to the grid’s positive sequence fault current contribution. In contrast to the zerosequence and negative-sequence currents, the changes appear to be significant compared to before the disturbance occurred. In the LL disturbance, the value of the positive sequence current from the grid after the steady state condition of the disturbance decreased to 2,855 Amperes, from before the disturbance was 2,923 Amperes. Meanwhile, the value of the positive sequence current from the PV inverter in the steady state condition of the disturbance decreased to 2,695 Amperes from the previous 3,022 Amperes. There was no negative sequence current value from the grid and PV inverter before the disturbance occurred, but after the disturbance, the value changed by 19.28 Ampere from the grid and 10.5 Ampere from the PV inverter.