Maximizing Hosting Capacity of Single-Phase Rooftop PVs in Unbalanced Distribution Systems

Increased installation of single-phase rooftop photovoltaic (PV) systems (SPPVs) and unbalanced loads in low-voltage distribution networks (LVDNs) may cause deterioration in the overall network performance. Major impacts include voltage unbalance, power losses, thermal overloading of lines, and other power quality issues. Therefore, it is crucial for robust integration coordination of SPPVs with proper sizing and placement to sustain the acceptable limits of power quality indices especially in unbalanced three-phase systems. This paper proposes an optimal capacity allocation of SPPVs method, which not only aids in minimizing the voltage unbalance, power losses, and lines’ overloads but also increases the hosting capacity (HC) of LVDNs. HC boosting enables to accommodating of an excessive capacity of SPPVs besides reducing the exchanged power through the utility grid. This work is demonstrated using an IEEE 123-bus unbalanced distribution system and simulated using daily curves of PV generations and load demands by co-simulation between MATLAB and OpenDSS platforms. Initially, the studied LVDN is divided into five operational zones, each zone has aggregated bulk generation of SPPVs switched only on single-phase. Then, the multi-objective grey wolf optimization (MOGWO) algorithm is operated to select the appropriate capacity, connected phase, and location of SPPVs at each operational zone. As a result, the voltage unbalance, power losses, and imported grid power, declined by 10%, 32% (31 kW at 100% overloading), and 26%, respectively. Further, the HC of LVDNs is increased by 185%, which highlights that the integration of SPPVs can improve power quality using accurate capacity allocation for bulk generation.