Analyzing Short-Circuit Current Behavior Caused by Inverter-Interfaced Renewable Energy Sources. Effects on Distance Protection

The short-circuit current behavior caused by renewable energy sources (RESs) connected to the grid through an inverter-interface is different from the behavior of conventional sources. Furthermore, there are effects on the distance protection of the transmission line coming from the RES. Therefore, an adequate and representative model of the inverter was developed in Matlab. This model simulates the control system in the inverter through an iterative process considering the dynamic voltage support characteristics that is governed by grid codes. As a result, short-circuit currents are obtained with greater precision, which allows more accuracy in the calculation of the impedance value seen by relays on the transmission line. Moreover, the analysis is developed by symmetrical and asymmetrical short-circuit calculations, taking into account the fault resistance variation and fault location. Finally, the analysis shows the main factors causing variations in the impedances seen and their behavior in distance protection zones.