Inertia Evaluation in Grid-Forming Converters Using Time-Domain Modeling

Grid-Forming (GFM) converters exhibit stability issues that worsen as the inertia coefficient increases. Novel power synchronization control methods have been proposed in the literature to improve GFM converters stability. Frequency-domain based inertia evaluation is typically used to adjust the control parameters of these methods, ensuring frequency responses align with the inertia and droop requirements outlined in the grid code. Therefore, the actual inertia performance of the converter highly depends on the accuracy of the inertia evaluation. In this paper, a straightforward inertia evaluation method using time-domain modeling is proposed. This method demonstrates that frequency-domain approaches can introduce errors, especially under high droop conditions. As a result, control parameters tuned using frequency-domain approaches may lead to a mismatch between the required inertia and the actual inertia, potentially violating the grid codes. In contrast, the proposed method helps in tuning the control parameters of GFM converter to achieve more accurate inertia behavior, ensuring grid codes compliance. Experimental and simulation results validate the effectiveness of the proposed method.