Technical Impacts of High Penetration of Solar Photovoltaic Systems in Low-Voltage Radial Distribution Network – Case Study

Rapid integration of Solar Photovoltaic (PV) based Distributed Energy Resources (DERs) at the distribution network has posed challenges to the grid operators since higher solar PV penetration coincides with the lower load demand, leading to issues like reverse power flow, overvoltage, harmonic current injection in the low-voltage (LV) network. In this paper, a realistic LV electric distribution network in the Kalmunai area, which is operated by the main utility provider in Sri Lanka, is modeled in ETAP software. The impact of PV penetration on transformer’s loading, power factor, power flow, power losses, and voltage profile of LV feeders are plotted and analyzed. Furthermore, the analysis is extended by considering various irradiance levels for different PV penetrations. Subsequently, the variation of voltage profile for solar PV concentrated feeder is plotted under various irradiance levels for different PV penetrations. The results indicate that overvoltage condition occurs at concentrated solar PV feeder, when the irradiance is high $\left(900 \mathrm{~W} / \mathrm{m}^{2}\right.$ and above), and the PV penetration is after the zero-crossing point. Additionally, the results show that reverse power flow occurs through the transformer when the aggregated solar PV active power generation exceeds the total active power demand of customers within the LV distribution network, which typically occurs during mid-day time (lower load demand time) when irradiance is higher ($\mathbf{9 0 0} \mathrm{W} / \mathrm{m}^{2}$ and above).