Fault operation of grid-forming converters with focus on system stability

Abstract

The increasing integration of renewable energies and battery storages into the electrical grid make new control methods for converters necessary. So called grid-forming converters open the possibility for fully converter based grids. Grid-forming converters have to cope with all kinds of disturbances like short-circuits. These pose the challenge of limiting fault currents in order to protect converters. In this paper we present a control scheme based on the virtual synchronous machine with two different methods of overcurrent protection. We show that fault currents can be limited in order to avoid additional hardware costs. Both methods show superior angular stability during and after the fault and are suitable for parallel operation with synchronous generators and synchronous condensers.