Transient effects of faults in high-voltage grids considering the share of grid-forming generation

The stability of a system influenced by power electronics depends to a large extent on the behaviour of the individual generation units. This behaviour in defined in the respective national grid codes. This requires a comprehensive and robust analysis of possible faults and occurring phenomena as well as the derivation of the necessary behaviour of the plants. Especially regarding the behaviour in the first periods after fault occurrence and fault clearance, there are still open aspects in current grid codes. The basis of the investigations in this paper 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. A toolchain is presented for the dynamic adaptation of derived networks and the analysis of identified faults, enabling large-scale electromagnetic transient (EMT) simulations to be conducted within modern power system analysis tools. Local and regional connection conditions are incorporated in the simulation framework. Subsequently, the transient behaviour of generating units in high-voltage power grids is investigated. The behaviour of a detailed modelling and an aggregated park model is compared and recommendations regarding necessary modelling depth is derived considering modelling complexity. The system behaviour and the influence of the fault cases is then combined with different shares of grid-forming (GFM) generating units to determine to what extent they can stabilize the system behaviour in the event of a fault and which levels of penetrations are necessary.