The European Union is working towards becoming greenhouse gas neutral by 2050. This involves reducing the carbon emissions from its electricity generation and electrifying sectors that previously relied on fossil fuels. For these reasons, the energy system is currently undergoing a massive transformation, with significant changes to infrastructure and technology. The number of conventional power plants connected via synchronous generators is steadily declining, with these being replaced by converter-based renewable energy systems. Moreover, the power system tends to be operated closer to its operational limits. Due to the changes in the system and in the way it is operated, dynamic stability limits can be reached earlier, in particular before the conventional steady-state operating limits, which makes grid dynamics increasingly important. The System Operation Guideline (SO-GL) addresses this issue by prescribing Dynamic Stability Assessment (DSA) by TSOs in Articles 38 and 39.

In the future, dynamic stability assessments must be considered in both real-time system operations and operational planning to assure stable system operation.

The German TSO TransnetBW conducts DSA as part of the grid planning process using the software application PowerFactory with planning models. In the last four years, TransnetBW developed and implemented the new software development PSIpassage/NEPLAN of PSI for DSA in real-time operation and operational planning. Viable simulation results are crucial to base future decisions on grid operation like redispatch and switching operations in the European synchronous area. The study presented here was performed to gain trust in the algorithms, the simulation results, and their visualisation by comparisons of the two calculation engines based on dynamized benchmark network models. Steady-state load flow calculations and contingency calculations first were analysed to demonstrate the differences and similarities between the tools. Subsequently, RMS simulations involving voltage controllers, turbine controllers, and power system stabilizers were conducted in compliance with the IEEE standards. The dynamic behaviour of the bus voltages, generator speeds, and rotor angles in the event of a three-phase short circuit on a line with fault clearing were analysed.

Our contribution will provide recommendations on parameterising the models and setting the reference variables for the controllers of the synchronous generators. We will discuss the effects of the simulation step size and the limits of agreement of the results, in particular with respect to the stability limit. Finally, we will compare the computation times for the two tools. This creates a basis for future comparisons of power systems with HVDC, phase-shifting transformers, or converter-based generation system models. Such comparisons can be performed to identify possible mismatches and issues in software tools and models and, thus, contribute to reliable DSA results.