Experimental short-circuit testing of grid-forming inverters in microgrid and interconnected mode

Power systems with increasing renewable generation are subject to intermittent, at times very high, penetration rates of power electronic generation plants. Grid-forming control schemes are potentially required to guarantee stability at high penetration rates. These schemes introduce voltage-source behavior and replicate the high fault currents of synchronous machines. Adapted control schemes have been developed to reduce fault currents of grid-forming inverters. This contribution presents experimental results on the short-circuit behavior of two grid-forming inverters, one commercial prototype and one experimental device. Two different operation modes, grid-connected and islanded, have been investigated and the different requirements are discussed along the results. The grid-forming schemes are potentially able to follow the same short-circuit requirements as current-controlled plants, but provide a fast inherent reaction to faults.