Impact of Distributed Generation's Fault Ride Through Strategies on System Stability in the Transmission Grid

This paper presents a new method for a detailed modeling of specific fault ride through (FRT) strategies according to the current grid code requirements for renewable energy sources (RES) connected to the low, medium and high voltage level based on an aggregated distribution grid model. By considering the aggregated distribution grid model, the impact of the distribution grid structures is analyzed. It is shown, that the current grid code requirements for the low voltage level cause high active power deficits resulting in high frequency gradients. In addition, progressive voltage sags can be observed, if the droop characteristic is set to k=2 value. Suitable countermeasures are implemented and the impact on power system stability is evaluated. A combination of an increased droop constant and a fast resynchronization of inverter based generation units connected to the LV level is identified as the most effective countermeasure.