Short-Circuit Analysis in Unbalanced LV Distribution Networks With Distributed Generators

The growing sensitivity to the climate impact due to the fossil fuels, used to produce electrical energy, supports the implementation and diffusion on large scale of Renewable Energy Source (RES) power plants, to support eco-sustainability and energy transition. Typically, Low Voltage (LV) distribution networks are supplied by the grid and by low size power plants, called Distributed Generators (DGs). The installation of several single-phase photovoltaic DGs, interfaced to the grid through DC/AC converters, from a rising number of users, increases the voltage unbalances of the electrical system, leading to the adoption of three-phase models of grid's components. Therefore, it becomes interesting for the literature, to study and characterize unbalanced networks in presence of multiple DGs, especially in fault conditions. In this paper, new parameters and indices are proposed to evaluate asymmetries due to short-circuit events, such as voltage sags and voltage swells. The proposed figures allow comparing the short-circuit conditions of the network without and with single-phase DG units so evidencing the impact of RES on the distribution network performance. The case study is performed on the CIGRE' LV test system.