The increasing integration of renewable sources, the installation of storage systems, and the growing demand for energy in distribution networks create the need for increasingly complex monitoring techniques. More timely and comprehensive monitoring of network parameters therefore becomes an imperative.

The optimal installation of synchronized monitoring systems, such as Phasor Measurement Units (PMUs), at critical points in the distribution network allows for better observability of the network than can be achieved through Remote Terminal Units (RTUs). In fact, the use of PMUs in the distribution network enables the integration of additional features in the network state estimation, such as estimation of line impedances, identification of network topology, including the identification of a portion of the network in isolation, as well as the identification of faults in the network.

The use of synchronized phasors and the ability to use quantities in Cartesian form in fact allows linear network models to be rewritten with a computational advantage. Despite these advantages, the complexity of low-voltage distribution networks, due to the large number of nodes and configurations and the possible unbalance of phases, creates the need for simplifications in the treatment of the estimation problem.

The work carried out in this report is divided into two parts and aims to identify and study possible methods for solving the state estimation problem in low-voltage networks. The first part concerns the study, development and implementation of a Weighted Least Absolute Value (WLAV) estimator. The developed estimator allows the direct elimination of invalid data and returns much more accurate estimates. A comparison between the WLAV estimator and the Weighted Least Square (WLS) estimator studied in the past three years was carried out, and the result obtained confirms that the WLAV estimator is better than the WLS estimator in terms of speed of execution and error abatement, providing a more accurate estimate of the state.

The second part covers the study, development and implementation of the state estimation of both a balanced and unbalanced three-phase network, enabling the true representation of a low-voltage distribution network with its complexities. I the case of the balanced three-phase distribution network, the state was estimated using PMUs provided at the different nodes of the network for the acquisition and monitoring of synchronized parameters. Considering zero current and voltage drop in the neutral conductor, the problem is solved in the same way as for WLS in the single-phase network, with the difference that in the three-phase network, the equations are tripled and the admittance matrix becomes three times larger, with results similar to a single-phase low-voltage network.

As concerns the unbalanced three-phase network, we considered the voltage drop between the neutral conductor and the earth, and the current circulation in the neutral conductor. Clearly, the problem is complicated by taking into account the contribution of the neutral conductor, having more equations and an even larger admittance matrix. The state is estimated again using synchronized measurements from PMUs based on the weighted least squares method.