Distribution Network Forecasting and Expansion Planning with Optimal Location and Sizing of Solar Photovoltaic Based Distributed Generation (Case Study Area: Yirgalem I Distribution Substation)

Abstract

Load forecasting is the prediction of demand for a future period, and it is a critical necessity for distribution system design and growth while also meeting all operational and technical constraints. Solar Photovoltaic (SPV) based Distributed Generation (DG) technology is the most direct way to convert solar energy into electrical energy without emitting carbon dioxide or causing greenhouse gas emissions. It also provides consumers with a reliable, clean, efficient, and continuous source of electrical energy. The integration of SPV DG changes the operating characteristics of modern power systems, resulting in significant economic and technical outcomes such as minimizing losses, and improving voltage profile. In this thesis, the peak load demand forecast for Yirgalem I distribution network for the years 2020/21- 2030/31 is done using least square extrapolation technique and the load growth rate of each feeder has been computed. In addition, from two-year average recorded data, the case study distribution feeder was identified as having higher interruption as compared to other feeders. As a result, Yirgalem town feeder has been chosen as a case study feeder. The modeling and simulation of this feeder has been carried out using ETAP software with and without integration SPV DG and sizing is done by Analytical method with the help of MATLAB program. The load flow result before integration showed that the total real and reactive power loss was 1.1133 MW and 0.5451 MVAR respectively with majority of bus voltages being outside the allowable range of 1??? 5%. Based on the Analytical approach and load flow analysis, SPV DG has been installed in the system at the appropriate capacity and location to reduce overall power losses, as well as to bring all node voltages within acceptable ranges. The proper site and size of the SPV DG were determined to be at bus 9 with a proper active power size of 7.86 MW and reactive power size of 4.03 MVAR. As a result, the percentage reduction of real and reactive loss was found to be 90.95% and 92.9% respectively with all bus voltages being within the limit and the minimum voltage at bus 24 improved from 0.8428 p.u to 0.9583 p.u. For further reduction of power loss, enhancement of voltage profile, and, economic benefits, the optimal size of SPV DG at two locations is considered with selected scenarios. Results show that the injection of 6.29 MW plus 3.23 MVAR at bus 9 and 1.57 MW plus 0.8 MVAR at bus 24, reduces the active and reactive power loss by 94.03% and 96.07%, respectively and the voltage profile improved drastically as compared to a single SPV DG location. Furthermore, SPV DG of the same size at two locations saves 359,961 Birr per year more than at a single location.