Benchmarking Classical Machine Learning Models for Shading-Fault Detection in Rooftop Photovoltaic Systems Using Real Sensor Data
Most published comparisons of machine-learning classifiers for photovoltaic (PV) fault detection are validated on simulated faults. We compare seven classical and ensemble-tree classifiers on the Réunion dataset, a 4 kW domestic rooftop plant on which shading faults were physically staged and logged. Readings within a staged episode are near-duplicates, so every train/test split is grouped by episode. A 20,800-row subsample that retains all 17 fault episodes was evaluated with three repeats of five-fold group-aware nested cross-validation, with synthetic minority oversampling (SMOTE) applied inside the training folds. Random Forest and XGBoost gave the highest mean accuracy (0.838 and 0.831) and Matthews correlation coefficient (MCC; 0.526 and 0.522). After Holm correction across the 21 pairwise Wilcoxon tests, only Random Forest's accuracy advantage over k-nearest neighbours and the multi-layer perceptron remained significant. Logistic Regression and the Decision Tree (accuracy 0.820) could be separated neither from the ensembles nor from the weakest models. SMOTE lowered binary MCC for six of the seven classifiers. Errors were concentrated in whole episodes: the Random Forest almost entirely missed four of the 17 fault episodes, including one of two uniform-shading and two of five intermittent-shading episodes. A post-hoc diagnostic shows that the no-fault rows were sampled over a wider range of times of day and output levels than the fault rows. Clock time alone reaches an MCC of 0.44, and PV-side voltage alone 0.72. The reported scores therefore reflect operating-condition differences as well as shading signatures. We release the pipeline and the diagnostics, and identify matched no-fault sampling as the step needed before the classifier ranking can be generalised.