## 1 Introduction
In another study, [PERSON], [PERSON] and [PERSON] (2015) [12] describe a way to analyse voltage unbalance sensitivity for different maximum sizes of a single-phase photovoltaic system (SPPS), with multiple PV penetration levels in a typical secondary radial distribution network in Spain. A stochastic assessment method is proposed to account for any random combination of SPPVSs in such a network. The results obtained by the authors show that the connection of SPPVSs (of a size up to 15 kW) is acceptable for a 5% PV penetration level. Overvoltage is one of the main voltage problems that may occur when distributed generation systems are connected in small residential areas. The impacts of PV penetration on LV distribution networks have been studied comprehensively, and several major issues are typically identified. [PERSON] and [PERSON] (2015) [15] present an overview of the advancement of power electronics converters in single-phase PV systems being commonly used in residential applications as well as control strategies. The problems that have been addressed are namely reactive power fluctuations and an increase in power losses, reverse power flow, voltage rise, voltage fluctuations, and the frequent operation of voltage regulation devices [17]. Solar PV impacts on LV three-phase distribution networks have been investigated using a comprehensive assessment tool by [PERSON], [PERSON] and [PERSON] (2012) [5]. This investigation revealed that PV output at midday may significantly change the network behaviour in terms of voltage rise, voltage unbalance, reverse power flows, and feeder losses. Usually, in the middle of the day, with peak PV output, feeder voltage profiles may improve heavily loaded phases, but there is still the risk of voltage rise and reverse power flow on low-loaded phases [5; 18]. Such voltage rise and voltage variation phenomena have a direct impact on consumers' appliances, but also on network equipment. Voltage variations cause frequent operation of line voltage regulators (VRs) and voltage-controlled capacitor banks for controlling the feeder voltage. Furthermore, also the tap changer (if it exists on the power transformer) keeps constantly being requested to change its position. This frequent operation shortens the expected life cycle of such devices and increases maintenance. The voltage unbalance factor relies on how the solar PV loads are dispersed in different phases of the LV distribution feeder [18]. Several studies were performed to determine the factors limiting the level of photovoltaic penetration on distribution feeders, and analyse their influence on network behaviour [9; 19; 20]. Voltage rise has been found to be one of the most important elements that limit the integration of high levels of solar generation in LV distribution systems [19]. There are methods dispensing the use of power flow analysis software for estimating the maximum PV generation that can be integrated into low-voltage feeders, while escaping excessive voltage levels. [PERSON], [PERSON] and [PERSON] (2016) [7] provide maximum PV generation estimates that are close to those calculated by such tools, while being easily implemented in a standard spreadsheet software. The example given for a low-voltage single-phase connection for a network based on Australian characteristics, estimated a 3.5 kW as maximum PV power for each PV system. As can be seen in the literature, it is a consented trend that as the total distributed PV power increases on many feeders, voltage problems are very likely to happen, especially as PV systems whose peak power is a significant fraction of the feeder capacity become more common. The limitations under which an unmanaged network could work are justified and pertinent areas of study. However, many of the studies that have been conducted so far, consider very specific networks, which makes it difficult to draw conclusions or realise their applicability to other scenarios.