The research activity described in this paper was aimed at validating through experimental tests the software tools needed to improve the observability of an electrical distribution network using measurements made by Phasor Measurement Unit (PMU). Specifically, methods for estimating grid state, estimating line impedances, identifying grid topology, and recognizing islanded operation were tested through RSE’s Distributed Energy Resources Test Facility (DER-TF). The purpose of the activity was not only to check the tools developed but also to analyze the actual ability of PMUs to be used to increase network observability.
From the results obtained, it is evident that measurements from PMUs alone allow reconstructing the state of the network by solving linear problems, with subsequent low computational cost.
In addition, the availability of both amplitude and phase measurements makes it possible to recognize islanded operation and identify line impedances.
The conducted analyses show that model errors result in errors in estimation due to different network layout or errors in cable nameplate data; however, they can be compensated for via PMU-based methods that allow reconstruction of uncertain network parameters. Nevertheless, it is clear that multiple measurements through PMUs are required to accurately estimate the network model; therefore, methods for optimal placement of PMUs should be applied in order to limit infrastructure costs and identify the minimum number of measurement points, considering the constraint of keeping the network observable under all expected operating conditions. Tests have also shown that different placement of PMUs does not affect the estimation results and thus the network state can be reconstructed with a smaller number of measurements and reducing infrastructure costs. It should be noted, however, that a limited number of voltage measurements can lead to high errors in estimation in the case of large measurement uncertainties or problems at a single PMU. For this reason, during the planning phase of the PMUs to be installed in the network, analysis should be done in a simulation environment to check how different measurement uncertainties and different errors may affect the estimator results. The results obtained from the experimentation demonstrated the effectiveness of the developed software tools. In addition, the activity resulted in an integrated infrastructure with the DER-TF that can be used for future developments and improvements of the estimation algorithms.