Modeling and assessment of large-scale solar PV generation on Uganda's electricity grid

Abstract

Globally, renewable energy sources like Solar PV are being employed more and more to ensure sustainable and cleaner future energy production. Uganda is endowed with abundant solar energy from the sun in Uganda, meaning that there is potential for integration of solar photovoltaic (PV) into the existing grid at transmission and distribution levels on a large scale beyond what is currently existing. Due to the intermittent (fluctuating) nature of Solar energy, its integration into the electricity grid creates a big impact on the power quality metrics (voltage, frequency, harmonics and power flow). This research therefore was aimed at investigating the impacts of integrating large scale solar PV generation on the Ugandan grid and determining the maximum possible penetration level of solar PV into the national grid by 2025. To achieve the objectives, data was collected mainly from UETCL and ERA. This data included historical demand data since 2013, and future grid development plans. DIgSILENT software was used to generate network models of 201, 2017, 2020 and 2025. The 2016 model was validated before being used as a base to build the other models. Load forecasting for 2017, 2020, 2025 scenarios was done with the aid of STATA statistical software. Each of the models of 2017, 2020, and 2025 were simulated at increasing solar PV penetration levels, carrying out load flow studies and static voltage stability studies per year. The results of the simulations were analyzed in excel software. The maximum allowable penetration level of solar PV into the national grid by 2025 was determined. The study revealed that integration of solar PV power had varying impacts on the different buses, lines and transformers. It caused increase in voltage levels at some buses and a decrease at others. This was found to be the same for the line loading, line losses and transformer loading. The static voltage stability was observed to improve with increasing Solar PV penetration level for each year. For the year 2025, increasing the penetration level from 185MW to 190MW caused voltage violations at some buses. The maximum allowable Solar PV penetration level was therefore observed to be 185 MW.