The stability of a system influenced by power electronics depends to a large extent on the behaviour of the individual generation units, which is defined in the respective national grid codes. This requires a comprehensive and robust analysis of possible faults, occurring phenomena and modes of action as well as the derivation and determination of the necessary behaviour of the plants taking into account realistically realizable requirements. Due to the complexity and speed of the control elements, the focus is increasingly on shorter time ranges and the transient behavior of plants. Especially regarding the behavior in the first periods after fault occurance and fault clearance, there are still open aspects in current grid codes.

Since a large part of the generation plants are connected to the distribution grids, the analysis of system stability and transient behavior must also take into account local and regional connection conditions.

In this paper, the transient behaviour of generating units in high-voltage grids is investigated by means of detailed EMT simulations.

The basis of the investigations is an extensive research of real-world events, which are categorized in terms of their manifestations and severity. The focus is on events that have led to the disconnection of generation units. Relevant event sequences such as voltage profiles, phase angle jumps and frequency gradients are subsequently implemented in the simulations. It turns out that phase angle jumps up to approx. 30 degrees were measured and also combined LVRT and HVRT events occurred in reality.

Synthetic, regional-specific distribution network models are then created and dynamised on the basis of publicly available data. Different network types are considered, which differ in terms of network size, supply task, penetration of generation plants or degree of cabling. Publicly available data are also evaluated for the modelling of generation units in order to enable a detailed mapping of park models, which takes into account the internal cable systems. The behaviour of a detailed modelling and an aggregated park models is compared and recommendations regarding necessary modeling depth is derived considering modeling complexity.

The system behavior and the influence of the fault cases is then combined with different shares of grid-forming generating units to determine to what extent they can stabilize the system behavior in the event of a fault and which penetrations are necessary for this. The grid-following and grid-forming units are modeled considering current limitation scheme and taking into account DC-side restrictions regarding available energy.