## Harmonic impact of high penetration photovoltaic system on unbalanced distribution networks – learning from an urban photovoltaic network

Solar photovoltaic (PV) system installations are rapidly increasing in distribution networks. These PV systems include power electronic devices which have an influence on the power quality of the grid in the form of harmonic distortion. The aim of this study is the harmonic impact of PV systems on distribution networks. A comprehensive harmonic behaviour analysis has been performed on the IEEE-13 bus distribution network with high PV systems penetration. A certain level of harmonics is also injected into the IEEE network through non-linear loads to resemble a realistic scenario. The investigation has been carried out through simulations of three case studies, namely PV system integrations at a single node in particular with and without the presence of background distortions in the supply and finally PV penetration at multiple nodes with supply distortions. Furthermore, an evaluation study has been conducted at the University of Queensland PV site to validate simulation results. This study has highlighted the PV systems harmonic contributions on real distribution networks and the impact of harmonics propagation on transformer *K*-factor. Results show that the total harmonic distortions of current and voltage are exceeding the limits when the number of PV systems increases, leading to transformer overloading and heating.