## 1 Introduction  
### Motivation  
The reduction in centralized power plants' energy production has been attributed to the emergence of distributed generation in electric distribution networks (EDNs), particularly at the low voltage (LV) level [1]. The increasing number of photovoltaic systems (PV) installed at the level of consumers (called prosumers) connected to low voltage electric distribution networks (LVEDNs) is expected to increase annually due to their various economic and technical advantages, besides the fact that they also can help reduce greenhouse gas emissions. However, distribution network operators (DNOs) are not fully prepared to integrate a very high number of PV prosumers with a variable character due to, on the one hand, the topologies of LVEDNs and, on the other hand, the ageing technical infrastructure [2]. A lack of voltage quality, defined by the number of incidences where voltages violate the admissible limits, has been identified by DNOs as their main concern in hosting more PV in their LVEDNs to accommodate the growing number of PV prosumers [3, 4]. Another uncertainty is the reverse power flow between the LVEDN and medium voltage (MV) EDN causing voltage level issues [5, 6]. DNOs should develop new strategies to address these issues and increase the penetration degree of PV prosumers. An overview of the strategies to improve voltage quality emphasizes that most of them belong to passive LVEDNs, without the renewable energy sources integrated. These strategies include replacing the no-load tap changing (NLTC)-fitted MV/LV transformers and reducing the cable impedances to decrease the excessive ratio between the resistance and the reactance of the LVEDNs. However, the expensive cost and the low efficiency from a technical point of view in the active LVEDNs (integrating the renewable energy sources) represent the weaknesses of these strategies [1; 7]. On the other hand, the high-frequency solar ramping caused by the rapid emergence and evolution of clouds can lead to over-voltages in LVEDNs [2]. Thus, the high intermittency of these sources could be a burden for DNOs in the voltage control of LVEDNs. As long as new strategies are not developed, the voltage violations could appear more and more often when a high number of PV prosumers are integrated, in conditions in which the voltage control band is usually between 0.9 and 1.1 p.u. of the rated voltage. Developing new strategies will require more advanced voltage control technologies, including smart devices/equipment that can process the data and help to identify the optimal solution [8]. The advanced voltage control technologies, integrated especially in the pilot LVEDNs, are represented by automatic voltage regulators [9; 10], energy storage systems [11; 12], capacitor banks [13; 14], or load balancing devices [15; 16]. However, before they can be implemented widely and correlated with each other, DNOs should do a cost-benefit analysis. One of the most efficient devices to ensure the resilience of voltage control is represented by the on-load tap changer fitted to the MV/LV distribution transformers [17; 18; 19; 20; 21]. These devices have demonstrated their performance in high (HV) and ultra-high (UHV) voltage electric transmission networks. The research carried out so far has not clearly defined the maximum PV hosting capacity of LVEDNs supplied from an EDS with an OLTC-fitted transformer. In these conditions, efficient strategies must be developed to increase as much as possible the limit threshold. Based on the aspects outlined above and the current context under which innovative energy solutions must be developed and implemented to fight climate change, we need to find a solution where more and more renewable sources are integrated into the existing EDNs. In this context, this paper will focus on developing an efficient voltage control solution to increase the penetration degree of PV prosumers quantified through the hosting capacity of LVEDNs.