Harmonic Modelling of a Grid-Forming Inverter in Stationary Frame

The increasing integration of inverter-based technologies for renewable energy resources demands advanced control strategies to ensure the stability and dynamic performance of future power systems. To facilitate effective control, converters commonly use rotating reference frames, such as the synchronous reference frame, allowing for easier system linearization and improved dynamic understanding. A solid grasp of these transformations is essential when designing and analyzing modern control algorithms, particularly grid-forming strategies. As grid-forming inverters aim to emulate the behavior of synchronous machines, their accurate admittance modeling becomes critical for understanding the system behavior and ensuring robust operation. This paper investigates the admittance shaping of a standard grid-forming control in the stationary frame to highlight the controller’s role in influencing the dynamic responses of the grid-forming unit. Special attention is given to the coupling effects between harmonic sequences, which can introduce significant challenges in unbalanced or fault conditions, thereby impacting overall control performance.