Evaluating the impact of solar photovoltaic generation on the power quality of mine power systems

Abstract

The South African mining industry utilises numerous high-power electrical machines to extract minerals from the earth's crust. The dependence of this industry on electricity necessitates the requirement of a reliable and high-quality energy supply around the clock to ensure efficient and safe mining operations. However, the looming crisis around the energy supply capability of the power utility, Eskom, escalating energy costs and South Africa's commitment towards the Paris Agreement on reducing greenhouse emissions are concerning towards the energy security required by the mining industry. Accordingly, after amendments in the generation limits for the private sector, renewable energy sources have become increasingly common within the South African mining industry to combat the previously mentioned problems. However, the integration of these renewable energy sources influences the power quality of the mine power system. The deterioration of power quality in the mine power system can have a profound impact on various aspects of mining operations, such as production interruptions due to equipment maintenance or failure, safety implications, and grid compliance issues. Of the identified renewable sources that are integrated into mine power systems in South Africa, solar PV systems are the most common. Due to the electronic nature of these systems, they have a high probability of impacting the power quality of the entire integrated power system. Therefore, there is a need to evaluate the power quality impacts of solar photovoltaic systems integrated into mine power systems, since the power quality impacts of this integrated system are largely underdetermined in the literature. The power quality impacts of solar PV integrated mine power systems were evaluated through the use of power system modelling software. This enabled the prediction of power quality changes from the integration of this system. A methodology was determined based on existing literature to meet the study objectives. In this dissertation, a solar photovoltaic integrated deep-level mine power system was simulated to determine potential power quality impacts. The power quality impacts were quantified by first determining the operation of the mine power system, before the integration of the solar photovoltaic system for voltages and power factors at the main substation bus, then simulating the integrated system to determine any power quality effects that are caused by the integration solar photovoltaic system. A deep-level mine case study was observed that adopted a 7.3 MW solar photovoltaic system without battery storage. An interactive power system simulation package was used and calibrated with empirical data obtained from the real-world mining power system. It was observed that the addition of the solar PV power plant affected the system voltage and power factor at the main substation bus, which is interfaced with the power utility. The simulation accurately predicted the system voltage and power factor of the integrated system, with results showing an increase in system voltage and power factors decreasing to concerning levels. This suggests that the addition of a solar photovoltaic powerplant with an existing deep-level mine power greatly affects the power quality of the systems especially during the time of solar power production.