Fig. 7
From: Revealing interactions between HVDC cross-area flows and frequency stability with explainable AI
Relation between frequency integrals and unscheduled flows indicates different HVDC operation modes. We show the feature importance of the frequency integrals, which is the mean absolute SHAP value normalized by the sum of all such values, i.e., it becomes one if the model uses only this single feature. The numbers indicate the feature rank within the respective model. For a specific area, the values \(\tau\) depict the correlation between the SHAP values of a frequency integral and the unscheduled outflows from this area, i.e., disturbance-like relations appear on the left side and control-like interactions on the right side. The strong control-like effects in the Britned and Estlink model probably relate to their uni-directional control scheme, while the weaker disturbance-like effects for Kontiskan and Storebaelt can be a result of the bi-directional application of frequency control