The provision of inertia through grid-forming capabilities of generation plants and battery energy storage systems is a key element in ensuring system stability. In addition to the established German certification framework for grid-code compliance, qualified plant reports are increasingly required for grid connections to the public extra-high-voltage network, particularly in the context of the rapid expansion of battery storage grid connections in Germany. Within these assessment reports, evidence must be provided regarding several grid-forming related electrical characteristics.

The required evidence must be demonstrated using detailed RMS and/or EMT models of the respective plants, whose components are to be modelled over a frequency range of at least 3 Hz to 2.5 kHz. For this newly defined verification process, this paper provides an experience report based on early grid connection processes and illustrates selected verification steps using a simplified fictitious plant model. In doing so, lessons learned regarding the emerging need for case-specific coordination among the project stakeholders are shared, and the practical applicability of the described guidelines is examined.