As the penetration of the powergrid with renewable energies like wind turbine generators (WTG) connected via power electronic devices is skyrocketing, concerns about the provision

of spinning reserve and frequency stability are emerging. The commonly used grid-following (GFL) controlling approach is, in its plain version, indifferent about frequency deviations.

The grid-forming (GFM) approach is a promising alternative to the latter and extends the application spectrum of inverter-based resources to act as a reference machine and to provide

system inertia. Whereas it is already feasible to use battery energy storage systems with GFM inverters within the grid, the application of the GFM scheme to WTG is more complicated

due to the constraints of the primary energy source. Further, sudden drops in the DC-link voltage of Type 4 generators can even interact with the mechanical parts of the wind turbine.

The control of the DC-link voltage of WTG can be done by the machine side converter or by the grid side converter. GFL-units typically use the grid-side converter for this purpose by

means of direct influence on active power feed-in.

The control of GFM inverters can only indirectly influence the feed-in power. This increases the interaction between the grid and the WTG, and events in the grid have a greater

impact on their mechanical parts. By using detailed grid and converter models and considering the DC power as an interface to the mechanics of the WTG, the effects of a controller

change on of the wind turbine can be estimated as a first approximation and parameter studies can be carried out without using a detailed model taking into account the mechanical and

aerodynamic part of turbine.

The objective of the model analysis is the systematic examination of a GFM WTG model and a GFL WTG model facing angular jumps. It makes use of the power system simulation

tool DIgSILENT PowerFactory and is applied in the EMT-Domain. The focus will be pointed at the GFM model, the accompagning GFL type will taken into account as a reference.

Further, a sensitivity analysis of relevant parameters in this situation will be performed. This aims at the determination of stability limitations. As it is more likely to occur

angular jumps at weak grid conditions, the test framework will also investigate the dependency of this simulation parameter. An outcome of the analysis will be a detailed report of

the processes within the analysed controllers during the angular jump.