Short-circuit calculations considering converter-controlled generation components

Converter connected units are to a large extent replacing conventional synchronous machines. Most grid codes require reactive current injection from converter-controlled equipment in the power system during fault condition. At present, there is no standardized way of calculating the short circuit level in a system with a high penetration of power electronic converters. In this paper, three different methods (IEC60909, superposition and iterative) have been tested on a grid model of the West Danish power system, which has a high wind power penetration. The short-circuit currents at the short-circuit location calculated by means of these three methods show the results with a negligible difference based on the present-stage system model. However, this is because the converter-controlled wind turbines (WTs) at present constitute 7% of the installed capacity in the model. It is foreseen that the total contributed short-circuit current will be larger as the share of the converter-controlled WTs increases. The result achieved using the iterative method is more reasonable because the grid-voltage support from the converter-controlled WTs is represented in the iterative method but not in the IEC60909 or the superposition method.