Impact of Increasing Distributed Solar PV Systems on Distribution Networks in South Africa

Authors: Aradhna Pandarum

Abstract:

South Africa is experiencing an exponential growth of distributed solar PV installations. This is due to various factors with the predominant one being increasing electricity tariffs along with decreasing installation costs, resulting in attractive business cases to some end-users. Despite there being a variety of economic and environmental advantages associated with the installation of PV, their potential impact on distribution grids has yet to be thoroughly investigated. This is especially true since the locations of these units cannot be controlled by Network Service Providers (NSPs) and their output power is stochastic and non-dispatchable. This report details two case studies that were completed to determine the possible voltage and technical losses impact of increasing PV penetration in the Northern Cape of South Africa. Some major impacts considered for the simulations were ramping of PV generation due to intermittency caused by moving clouds, the size and overall hosting capacity and the location of the systems. The main finding is that the technical impact is different on a constrained feeder vs a non-constrained feeder. The acceptable PV penetration level is much lower for a constrained feeder than a non-constrained feeder, depending on where the systems are located.

Keywords: Medium voltage networks, power system losses, power system voltage, solar photovoltaic, PV.

References:

[1] A. Pandarum, G. Lekoloane and D. Milazi, "Trends and statistics of Solar PV distributed generation in SA," in The Sustainable Energy Resource Handbook Vol 9, Alive2green, 2019, pp. 21-27.
[2] V. H. M. Quezada, J. R. Abbad and T. G. S. Román, "Assessment of energy distribution Losses for increasing penetration of Distributed generation," IEEE, vol. 21, no. 2, 2006.
[3] R. Shayani and M. de Oliveira, "Photovoltaic Generation Penetration Limits in Radial Distribution Systems," IEEE Transactions on Power Systems, vol. 26, no. 3, pp. 1625-1631, 2011.
[4] H. Pezeshki, P. Wolfs and G. Ledwich, "Impact of High PV Penetration on Distribution Transformer Insulation Life," IEEE Transactions on Power Systems, pp. 1-9, 2013.
[5] H. Beltran, E. Perez, N. Aparicio and P. Rodríguez, "Daily solar energy estimation for minimizing energy storage requirements in PV power plants," IEEE Transactions on Sustainable Energy, vol. 4, no. 1, p. 474–481, 2013.
[6] P. Mohammadi and S. Mehraeen, "Challenges of PV integration in low-voltage secondary networks," IEEE Transactions on Power Systems, vol. 32, no. 1, pp. 525-535, 2017.
[7] Q. Alsafasfeh, O. Saraereh, I. Khan and S. Sunghwan Kim, "Solar PV Grid Power Flow Analysis," Sustainability, 2019.
[8] S. Hashemi and J. Østergaard, "Methods and strategies for overvoltage prevention in low voltage distribution systems with PV," IET Renewable Power Generation, vol. 11, no. 2, pp. 205-214, 2016.
[9] C. Trueblood, S. Coley, T. Key, L. Rogers, A. Ellis, C. Hansen and E. Philpot, "PV measures up for fleet duty," IEEE Power and Energy magazine, pp. 33-44, 2013.
[10] K. Turitsyn, P. Sulc, S. Backhaus and M. Chertkov, "Distributed control of reactive power flow in a radial distribution circuit with high photovoltaic penetration," 2010.
[11] M. Alam, K. Muttaqi and D. Sutanto, "A Novel Approach for Ramp-rate Control of Solar PV Using Energy Storage to Mitigate Output Fluctuations Caused by Cloud Passing," IEEE Transactions on Energy Conversion, vol. 29, no. 2, pp. 507-518, 2014.
[12] A. Mubaraki, "Impact of photovoltaic system penetration on the operation of voltage regulator equipment," California Polytechnic State University, 2013.
[13] M. McGranaghan, T. Ortmeyer, D. Crudele, T. Key and J. Smith, "Renewable Systems Interconnection Study: Advanced Grid Planning and Operations," Sandia National Laboratories, 2008.
[14] K. Alboaouh and S. Mohagheghi, "Impact of Rooftop Photovoltaics on the Distribution System," Hindawi Journal of Renewable Energy, 2020.
[15] S. A. B. o. Standards, "NRS 048 Part 2: Voltage characteristics, compatibility levels, limits and assessment methods".
[16] M. ElNozahy and M. Salama, "Technical impacts of grid-connected photovoltaic systems on electrical networks - A review," J. Renewable Sustainable Energy, 2013.
[17] E. Mulenga, "Impacts of integrating solar PV power to an existing grid: Case Studies of Mölndal and Orust energy distribution grids," 2015.
[18] South African Grid Code Secretariat, "South African grid connection requirements for Renewable Power Plants (RPPs) 3.0," 2019.
[19] South African Bureau of Standards, "NRS 048 Quality of Supply".
[20] Eskom, "DST 34-542: Distribution Voltage Regulation and Apportionment Limits".
[21] South African Bureau of Standards, "NRS 097-2-1 Small Scale Embedded Generation: Utility interface," 2017.