Improving, Modelling and Simulation of Droop Controller for Grid-forming Inverters in DIgSILENT PowerFactory

Since more and more large conventional power plants, based on direct coupled synchronous generators (SGs), will be phased out in the future, frequency stability must be guaranteed. Consequently, grid-forming inverters are needed to ensure the system stability of the future grids. In the joint research project ""VerbundnetzStabil"", conducted by Fraunhofer ISE and its partners, the stability of a grid system with a high penetration of inverter-based renewable energy sources (RES) is investigated. This paper aims to develop a droop control concept of grid-forming inverters that can stabilize the system under all future grid scenarios (e.g. grid systems can be split into sub-grids with up to 100% RES and high-power transmission). The droop control structure is presented in both synchronous and stationary frames. Moreover, the droop control scheme is modelled and simulated in DIgSILENT PowerFactory with different test cases.