On The Implementation of an FRT Strategy for Grid-Forming Converters Under Symmetrical and Asymmetrical Grid Faults
Roberto Rosso, Soenke Engelken, Marco Liserre
Abstract
Recent studies have shown the potential benefits of grid-forming (GFM) converters and their capability of stabilizing a power system with high penetration of power electronics-based generation. A crucial aspect of any GFM converter control strategy will be the handling of fault-ride through (FRT) scenarios, which converters for generation sources will face regularly in the field. In this article, an FRT strategy for GFM converters is proposed, which respects the converter hardware limitations (i.e., current limitations) while maintaining GFM behavior even during “protective” operating modes. The FRT strategy addresses both symmetrical and asymmetrical faults and is compliant with recently proposed draft grid codes requirements published by the British system operator NGESO. The issues related to FRT of GFM converters are first discussed in detail, then a proper strategy is presented and its effectiveness is demonstrated by means of an extensive power-hardware-in-the-loop measurement campaign, showing its efficacy even against severe fault conditions.