Electric vehicle supply infrastructures represent a valid mean to integrate and encourage electric mobility, ensuring safe integration of electric vehicle (EV), renewable sources, and controllable devices. Management of these infrastructures under DC microgrid framework is affected by EV usage pattern, involving stochastic features, and by vehicle-to-grid ability, yielding the need of suitable operation strategy assessment. This article is focused on the analyses of day-ahead performances of a DC microgrid based on the solution of different optimization algorithms, involving technical and economic targets. The study involves statistical analyses concerning EVs usage, based on historical dataset, with the aim to generate scenarios to be investigated. Performances are compared by means of technical and economic indicators. The considered layout of DC microgrid refers to a realistic installation.

Global earthing systems (GESs), which are created by the interconnection of local earthing systems, should guarantee the absence of dangerous touch voltages. According to international standards, one of the reasons for this safety characteristic of GESs is that medium-voltage and low-voltage grounding systems form a quasi-equipotential area. Typical examples of GESs are in city centers due to the high number of interconnected grounding systems in the area. For this reason, in addition to ground grids, other metallic parts with different primary functions shall be also considered, e.g., water and gas pipes, tramway tracks, and building foundations can modify the electric potential distribution in the area. In this paper, a model based on the Maxwell's subareas method (MaSM) is used to evaluate how buried metallic parts, which are not intentionally connected to ground grids, modify the electric potential on the soil surface. First, the MaSM model is validated with experimental measurements on a simple electrode configuration. The measured voltages are compared with the MaSM results and with the results obtained with a finite-element method model simulated with COMSOL Multiphysics. Then, the simulations are carried out on a realistic urban test case.

When a single line to ground fault (SLGF) happens on the MV side of an HV/MV system, only a small portion of the fault current is injected into the ground by the ground grid of the faulty substation. In fact, the fault current is distributed between grounding electrodes and MV cables sheaths. In systems with isolated neutral or with resonant earthing, this may be sufficient to provide safety from electric shock. Experimental measurements were performed on a real MV distribution network: a real SLGF was made and fault currents were measured in the faulty substation and in four neighboring substations. In this paper, the problem of fault current distribution is introduced, the test system is described and the measurements results are presented.

In this paper a decentralized power regulation approach is presented for converters operating in DC microgrids. The method enables classical droop control to perform power regulation tasks by employing auto-adaptive virtual resistances for the controlled devices. Moreover, the auto-adaptive nature of the droop characteristic is employed to constraint, through a decentralized approach, the microgrid DC bus voltage within an admissible range of values, despite unpredictable changes in the operating conditions of the microgrid (i.e., sudden variations in load and/or in renewable production). The proposed approach is formalized as a multi-objective optimization problem whose solution is entrusted to a method based on dynamic system theory and Lyapunov theory. Simulations are carried out on test DC microgrids, in order to prove the approach effectiveness.

International Standards define a Global Earthing System as an earthing net created interconnecting local Earthing Systems (generally through the shield of MV cables and/or bare buried conductors). In Italy, the regulatory authority for electricity and gas requires distributors to guarantee the electrical continuity of LV neutral conductor. This requirement has led to the standard practice of realizing “reinforcement groundings” along the LV neutral conductor path and at users' delivery cabinet. Moreover, in urban high-load scenarios (prime candidates to be part of a Global Earthing System), it is common that LV distribution scheme creates, through neutral conductors, an effective connection between grounding systems of MV/LV substations, modifying Global Earthing System consistency. The aim of this paper is to evaluate the effect, in terms of electrical safety, of the aforementioned LV neutral distribution scheme when an MV-side fault to ground occurs. For this purpose, simulations are carried out on a realistic urban test case and suitable evaluation indexes are proposed.