Voltage sag estimation based on probabilistic short circuit including the fault ride through effect of distributed generator

Short circuit (SC) fault is one of the most severe disturbances faced by the power system. SC faults not only lead to high SC currents but also cause voltage sag in a wide area. In this paper the voltage sag problem caused by SC fault are estimated based on the probabilistic SC concept. The research is based on a typical Dutch Medium Voltage distribution grid where the penetration of Distributed Generation (DG) is experiencing rapid growth. Fault Ride Through (FRT) capability will be obligatory for all types of DG system in future grid code which is different with currently situation. However, SC contribution from Voltage Source Converter (VSC) based DG is neglected according to IEC 60909 standard and there is no available model to consider FRT behavior of VSC-DG yet in the simulation software DIgSILENT PowerFactory. Therefore an equivalent model is developed in PowerFactory in order to emulate VSC-DG´s FRT capability and study its effect on the voltage sag estimation results. The simulation results show that the probability of occurrence of severe voltage sag is reduced and the system overall voltage sag performance is improved both due to the voltage support effect during FRT.