The increasing share of converter based resources (CBRs) in electrical power systems, in particular the widespread deployment of grid following (GFL) inverters, leads to a progressive reduction of system inertia and can challenge angle, voltage, and frequency stability. So far, the remaining synchronous generators have largely masked these effects, but with their expected phase out, alternative mechanisms for providing grid supporting behaviour are required. Grid forming (GFM) control concepts for CBRs have been proposed as a key solution, yet their impact on system level dynamics under realistic operating conditions is still not fully understood. However, these efforts largely lack a common, structured basis, making it difficult to compare results across studies, control implementations, and grid configurations. This absence of comparability impedes both the systematic evaluation of GFM performance and the derivation of generalised conclusions relevant to real grid applications. Addressing this gap is a central motivation of the present work.

This work develops an automated EMT (electromagnetic transients) simulation framework in DIgSILENT PowerFactory, controlled via the Python API, to systematically investigate the influence of GFM operated CBRs during different grid conditions. The framework covers a structured set of practically relevant disturbance scenarios, including short circuits, loaded line disconnections, system splits, and islanding processes. Furthermore, more generic events as phase angle jumps or forced frequency ramps are under investigation. A structured sensitivity analysis is performed with respect to key GFM parameters, including the accelerating time constant of the virtual synchronous machine (VSM), damping characteristics, and droop settings. The framework is applied to a real German high voltage distribution grid. The simulations are designed to support an upcoming field test in which battery inverters operated in GFM mode will be evaluated in interconnected operation, in planned islanded operation, and in small restoration islands.

All simulations are carried out in the EMT domain with distributed parameter line models. Generic EMT type inverter models are employed, including power controllers, inner voltage and current controllers, and basic current limiting functions. The paper presents the automation workflow and compares results for different GFM CBR penetration levels in the benchmark system, highlighting their impact on dynamic performance and stability margins. For the real grid, the analysis identifies practically relevant sensitivities and examines the interaction of GFM CBRs with remaining synchronous machines in both interconnected and islanded operation. Beyond the specific case studies, the proposed framework is intended as a reusable basis for researchers and practitioners investigating the introduction and large scale deployment of distributed GFM CBRs in future power systems.