Probabilistic Voltage Harmonic Compliance-Margin Forecasting with Adaptive Conformal Prediction at Low-Voltage Distribution Points of Common Coupling

Increasing deployment of power-electronic loads has intensified the need for short-horizon forecasting of voltage harmonic distortion at low-voltage points of common coupling. This study develops a telemetry-first framework for forecasting phase-wise voltage total harmonic distortion (UTHD) and its compliance margin using routinely retained 10 min power-quality indices. Independent histogram-based gradient-boosting regressors (HGBRs) were trained for 10, 30, 60, and 120 min horizons using leakage-controlled chronological validation and were benchmarked against persistence, seasonal and climatological references, Ridge, autoregressive integrated moving average (ARIMA), bidirectional long short-term memory (BiLSTM), target-history-only HGBR, XGBoost, and LightGBM. Forecast uncertainty was quantified using symmetric conformal prediction with calibration-only selection of adaptive residual parameters. Across the three Córdoba phases, the common-feature HGBR achieved mean MAEs of 0.198, 0.225, 0.232, and 0.258 percentage points at 10, 30, 60, and 120 min, respectively, and consistently outperformed persistence. The selected conformal configuration achieved mean empirical coverages of 90.55–88.77% for nominal 90% intervals and 95.15–94.17% for nominal 95% intervals across increasing horizons. These findings show that index-level telemetry can support accurate multi-horizon UTHD forecasting with empirically calibrated predictive uncertainty for forecast-informed harmonic monitoring.