## 1 Introduction  
Distribution networks play a fundamental role in electric power systems, which is why reducing their losses and minimizing investment costs are among the greatest challenges faced by current systems [1]. When the voltage level increases, the current circulating through the network decreases, therefore reducing the losses caused by the Joule effect. In the particular case of distribution networks, the voltage is reduced in such a way that the current circulating through the network is higher. This effect generates greater losses, despite being necessary, given that reducing the voltage levels has a significant impact on distribution networks' design and investment costs. In the same way, these losses have an incidence on the power factor, given that the generators are responsible for covering the total demand (i.e., including these losses). This causes greater uncertainty in energy planning, which increases the design difficulty of a distribution network. The above has an effect on the overruns that must be assumed by the network operator and, therefore, by the users [2]. Distributed generation (DG) may be regarded as the best option for reducing power losses. However, its initial installation costs can be very high, especially when compared to strategies such as the reconfiguration and connection of branch capacitors [3]. The main issue with capacitor banks is that they inject power in fixed reactive power steps, which does not contemplate a dynamic daily active and reactive power demand scenario along electrical distribution networks [4]. The use of power compensation techniques by means of devices that implement power electronics has allowed for the development of strategies that consider system dynamics in order to present increasingly efficient solutions in the search for loss reduction [5]. In this particular case, a focus on power electronics devices was chosen, specifically on D-STATCOMs (Distribution Static Compensators), which are connected in parallel to the network [6]. Among the main features of these compensators, the reactive power absorption or injection by varying the phase amplitude and angle with respect to the connected network can be highlighted. All this, as a function of the demand behavior [7]. These devices may be located at any node of the network. Nevertheless, it is necessary to determine their location and sizing, so that a considerable decrease in network losses may be achieved. The implementation of D-STATCOMs has the following advantages: (i) high reliability, (ii) low operating costs, and (iii) durability (typically between 5 and 15 years) [5]. The specialized literature presents different reports on the optimal siting and sizing of D-STATCOMs in distribution systems. Some of these works are described below. The authors of [8] proposed a multiobjective particle swarm optimizer that considers the reconfiguration of the electrical network in order to locate and size D-STATCOMs while analyzing the minimization of power losses (objective function), voltage stability, and the loadabilty factor of distribution lines. The main aspect of the aforementioned article is that the optimization process is only carried out under peak load conditions, which could lead to oversizing in the D-STATCOMs.The authors of [9] present a combination between a genetic algorithm and a mathematical programming method based on second-order cones in order to place and size D-STATCOMs in distribution networks. The main contribution of this work is the utilization of industrial, residential, and commercial demand curves. The results obtained in the IEEE 33- and 69-node systems show the effectiveness of the proposed methodology in comparison with the solution of the exact model in the GAMS software. The authors of [7] present a complete review of the specialized literature with regard to the optimal placement and sizing of D-STATCOMs in distribution systems. The main contribution of this work is the classification of the different existing methodologies for solving the problem.