Short circuit (SC) fault is one of the most severe disturbances faced by the power system. The traditional worst cases based SC calculation concept ignores the random nature of factors affecting SC current and only gives maximum and minimum SC current results. In this paper, the stochastic behavior of factors such as fault location, fault type and fault impedance is considered and results in the probabilistic SC concept. SC faults not only lead to high SC current but also cause voltage sag in a wide area. Therefore the current and voltage problems caused by SC fault are estimated together based on the probabilistic SC concept. The research is based on a typical Dutch Medium Voltage distribution grid where the penetration level of Distributed Generation (DG) is experiencing rapid growth. Fault Ride Through (FRT) capability will be obligatory for Voltage Source Converter (VSC) based DG in future grid code which is different with currently situation. Therefore an equivalent model is developed in PowerFactory in order to emulate VSC-DG's FRT capability, calculate its SC current contribution and study its effect on the current and voltage results both. The simulation results show that the grid contributed SC current is reduced due to VSC-DG's FRT and the voltage sag performance is improved because of the voltage support effect during FRT.
Probabilistic short circuit calculation and its application in voltage sag estimation considering fault ride through of distributed generator
Li, M. (Author). 31 Aug 2014
Student thesis: Master