## 1 Introduction  
The global photovoltaic (PV) market has grown rapidly over the past decade at a steadily increasing rate, which will lead to PV becoming one of the major sources of power generation for the entire world [1]. However, as the share of electrical energy generated by distributed resources increases, concerns height over the potential for such resources to create voltage unbalances (V\({}_{\text{Unb}}\)) and voltage violations on electrical distribution feeders [2; 3; 4]. When the power generated from distributed resources exceeds the load on a certain feeder or section of it, voltages may rise on that section. Moreover, distributed generation coupled with the existing load demand may cause congestions, feeder currents to approach, and even exceed rated currents. Furthermore, single-phase connections may contribute to a voltage increase in one phase, but to a decrease in another, making the system potentially unbalanced. Such an unbalance degrades the performance and shortens the life of certain equipment, such as motors, and may cause current unbalance, which leads to torque pulsations, increased vibrations, mechanical stresses, and increased losses, resulting in lower efficiency and winding overheating. Power quality studies referring to PV generation limits in low voltage (LV) have been a topic extensively covered in the scientific community, with some referring to voltage unbalance specifically as the main concern [5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16]. A study [16] considering a Canadian network used in suburban residential areas defined voltage variation limits and evaluated PV penetration limits. The results indicated that the PV penetration level should not adversely impact the voltage on the grid when the distributed PV resources do not exceed 2.5 kW per household on average on a typical distribution grid. It is important to bear in mind that the PV penetration has different effects when introduced in different points of the network [5; 6; 7], but also when either a single PV installation is considered or multiple PVs in the same phase are connected. Even though this effect exists, it does not seem to be as important as the PV size itself and the subjacent load applied [8]. Such phenomena has also been studied by [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] (2011) [13] where voltage unbalance sensitivity analysis and stochastic evaluation was performed, based on the ratings and locations of single-phase grid connected rooftop PVs in a residential LV distribution network. For a single PV installation and for a feeder supplying up to a 1-MW load, the results show that a rooftop PV (with less than 5 kW) could cause network voltage unbalance to increase by 0.1%, if installed at the beginning of the feeder For the same installation, the results increase 25% instead if the rooftop PV is installed at the end of the feeder. The authors show that the voltage unbalance factor (VUF) in a feeder rises rapidly as the PVs are added. However, adding PVs in other two feeders causes an increase in the value, but this is not as significant as the increase with the size of the PVs. [PERSON], [PERSON], [PERSON] and [PERSON] (2013) [9] refer to the penetration of PV as a measure of peak load. For 86% of the cases simulated, maximum PV penetration was at least 30% of peak load without exceeding 2% of unbalance. [PERSON] and [PERSON] (2014) [10] present a study on voltage unbalance due to the increased rooftop PV installations on a low-voltage residential distribution system considering three cases. In all the power, the demand of the load is light and the percentage of PV penetration is varied from 0 to 100% of the feeder capacity. The PV's installation is either considered in phase A, phase A and B, or in all of the phases. In Case 1 and Case 2, the results are similar, and the voltage unbalance of 2% is exceeded around 40% of penetration. However, in Case 3, the voltage unbalance never exceeded the standard limit.