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Distributed generation (DG) produces many benefits for the distribution systems that are operated as active systems, even if they have been traditionally designed as passive networks. Then, new technical issues must be addressed, involving both normal and abnormal operating conditions such as short circuits. Photovoltaic systems (PVSs) are among the most diffuse DG and their contributions to the short-circuit operating conditions depend on several factors, such as environmental conditions, PVS inverter control characteristics, self-protection systems, and fault location and type. An analytical model that aims at quickly and accurately analyzing the three-phase short-circuit operating conditions in a distribution system in presence of PVSs is presented in this paper. The model is applied to a typical North American MV network characterized by large penetration of PVSs, investigating the influence of the aforementioned factors.

Nowadays, the development of the hybrid microgrids is mainly addressed towards industrial applications, where different AC and DC typologies of distributed energy resources coexist. In a such context, the management of devices in the hybrid AC/DC microgrid becomes a not-obvious task, that has gained great interest in relevant literature. In this paper, the importance of the optimal management of both active and reactive powers in an hybrid AC/DC microgrid is analyzed, highlighting that, in these applications, the reactive power control is mandatory not only when the microgrid operates in islanding mode, but also in grid-connected mode. Specifically, a comparison between control strategies with and without reactive power management is performed in the hybrid AC/DC microgrid proposed for an actual industrial facility in the southern Italy. Numerical experiments demonstrate the need of utilizing the former strategy than the latter one.

In this paper, we address the problem of the probabilistic steady-state analysis of an electrical distribution system that includes wind and photovoltaic power plants. We propose a new method that takes into account the uncertainties due to the time variations of power load demands and the random nature of solar and wind energy. The new method extends a probabilistic approach proposed in the relevant literature for balanced electrical distribution systems to unbalanced electrical distribution systems, and it also takes into account the correlation among the random input variables. The method is based on Taguchi's orthogonal arrays. Numerical applications based on an IEEE test system provide evidence of the probabilistic performance of the proposed approach. The results obtained with the proposed method are compared with the results obtained using non-linear Monte Carlo simulation and the Point Estimate Method.

In this paper, a probabilistic method is proposed to analyze the steady-state operating conditions of an active electrical distribution system with Wind (WD) and Photovoltaic (PV) generation plants. This method takes into account the uncertainties of power load demands and power production from renewable generation systems and combines Monte Carlo simulation techniques and multi-linearized power flow equations. The power flow equations include models of wind turbine and PV generation units and multi-linearization is accomplished by applying a criterion based on the total active power of the system. The method properly extends a probabilistic method proposed in the relevant literature for traditional passive electrical distribution systems to the field of an active electrical distribution system with WD and PV generation units. Numerical applications are presented and discussed with reference to a 17-bus test distribution system characterized by WD and PV systems connected at different busbars. The results obtained with the proposed algorithm are compared with the results obtained using a Monte Carlo simulation algorithm that included non-linear power flow equations.