Sensitivity Quantification for Distribution System State Estimation
For researchers and practitioners in power systems, this work highlights a previously overlooked sensitivity in DSSE uncertainty quantification, though the findings are incremental as they confirm known limitations of WLS under non-Gaussian assumptions.
This paper investigates whether the uncertainty bounds assumed by weighted least squares (WLS)-based distribution system state estimation (DSSE) are sensitive to distributional assumptions of pseudo-measurements, and proposes a diagnostic framework using the Fisher Information Matrix. Experiments on the CIGRE MV network show that heavy-tailed and skewed distributions cause WLS to systematically overstate uncertainty bounds, with miscalibration varying across buses and scenarios.
Pseudo-measurements are the dominant source of uncertainty in distribution system state estimation (DSSE), yet their distributional assumptions are treated as fixed inputs by existing uncertainty quantification methods. This paper investigates whether the uncertainty bounds assumed by weighted least squares (WLS)-based DSSE are sensitive to these distributional assumptions, and whether this sensitivity is quantifiable using the Fisher Information Matrix (FIM). We propose a diagnostic framework that compares the true Cramér-Rao Bound (CRB) against the WLS-assumed CRB via a per-bus, per-scenario ratio, computed directly from the converged WLS solution. Pseudo-measurement distributions are varied across five types in 22 variants matched at equal spread to isolate shape effects from variance. Experiments on the CIGRE MV network across 100 operating scenarios yield three findings. First, heavy-tailed and skewed distributions show consistently that WLS systematically overstates its uncertainty bounds. Second, the degree of miscalibration varies across buses and operating scenarios, confirming that distributional sensitivity is not uniform. Third, the CRB ratio is structurally blind to mean-shift bias, exposing a fundamental limitation of variance-based uncertainty diagnostics. Together, these results confirm the hypothesis and show that the choice of pseudo-measurement distribution directly distorts the confidence limits under WLS-based assumptions, which must be explicitly accounted for in any uncertainty-aware DSSE method.