Single-Phase PV Power Injection Limit due to Voltage Unbalances Applied to an Urban Reference Network Using Real-Time Simulation

Abstract

As photovoltaic (PV) penetration increases in low-voltage distribution networks, voltage variation may become a problem. This is particularly important in residential single-phase systems, due to voltage unbalances created by the inflow of points in the network. The existing literature frequently refers to three-phase systems focusing on losses and voltage variations. Many studies tend to use case studies whose conclusions are difficult to replicate and generalise. As levels of residential PV rise, single-phase PV power injection levels, before voltage unbalances reach standard limits, become important to be investigated. In this study, an urban European reference network is considered, and using a real-time digital simulator, different levels of PV penetration are simulated. PV systems are connected to the same phase (unbalanced case), and are also evenly phase-distributed (balanced case). Considering a 2-3% unbalance limit, approximately 3.5-4.6 kW could be injected in every bus in an unbalanced scenario. With a balanced PV distribution, the power injected could reach 10-13 kW per bus. Buses closer to the power transformer allow higher power connections, due to cable distances and inferior voltage drops. Feeder length, loads considered during simulation, and cable shunt capacitance reactance influence the results the most.

Active Power Management for PV Systems under High Penetration Scenario

“…It is assumed an axial grid connection since it is the most typical configuration in an LV distribution network in a resident area [44]. There are different grid configurations described in other works [14,21,45]. A typical residential cluster is considered, which is illustrated in Figure 1(a).…”

“…Different studies deal with the effects of high PV penetration into the electric grid [15][16][17][18][19][20]. The most important effect is the variation in the voltage level [15][16][17][18][19][20][21]. The relevance of this problem is that the safe operating area of sensitive electronic equipment such as computers or medical devices may be lost [22].…”

A Comparative Study into Enhancing the PV Penetration Limit of a LV CIGRE Residential Network with Distributed Grid-Tied Single-Phase PV Systems

“…According to the European PV connection guidelines, the installed PV capacity should not exceed the contracted power [24]. Therefore, for simplicity, it is assumed that installed PV penetration depends upon the rated load of load buses, and based on this, different PV penetration levels are analyzed.…”

System Unbalance Analyses and Improvement for Rooftop Photovoltaic Generation Systems in Distribution Networks

“…As levels of residential PVGSs rise, single-phase PVGSs levels also increase. The approximate PV capacities can be installed considering a 2-3% voltage unbalance limit under unbalanced and balanced PVGS placements were estimated in [14]. The voltage unbalance (VU) leading to overheating and fast thermal ageing has a harmful effect on the loads and equipment connected to grids.…”