To reduce the complexity of multiarea power systems during power flow study and security assessment, equivalencing of external power systems is essential. In this paper, external power systems are modeled as adaptive loads representing the tie-line flows varying with system operating conditions. The fuzzy inference system tuned by hybrid genetic-simulated annealing (HGSA-FIS) is proposed to predict the active and reactive power of adaptive loads from forecasted renewable energy (RE) generation and loads demand. The performance of proposed equivalent has been evaluated with an RTS-GMLC by comparing the power flow results in the internal system before and after equivalencing under varying RE and load demand scenarios. The results demonstrate the robustness of HGSA-FIS-based equivalent under varying RE generation and load demand. Furthermore, the proposed equivalent performs close to ANN-based equivalent and outperforms ANFIS-based equivalent. To practically implement the proposed approach, the neighboring system operators are required to exchange only the forecast data of RE generation and load demand, and the equivalent needs to be updated upon major grid changes.
Only a small number of Ethiopia’s rural population has access to electricity. These rural areas can be electrified using different electrification approaches. One of the prime challenges in the decision making process is to obtain reliable information about the energy potential of the region under consideration. In this paper, an assessment of the solar energy potential of East Gojjam Zone in Ethiopia is presented. In the study area, there are only four meteorological measurement stations, namely: Debre Markos, Debrewerk, Mota, and Yetnora. The data for the hours of sunshine for these sites is collected from the National Meteorological Agency, Bahir Dar Branch Office. The data is prepared and used to calculate the mean global horizontal solar radiation using Angestrom-Prescott (AP) Model. An AP model for the four study sites was developed. The model regression coefficients, a and b, are estimated for each study site for respective latitudes, average hours of sunshine and day length. According to the models, the annual mean daily global horizontal radiation for Debre Markos, Debrewerk, Mota, and Yetnora is 5.88, 6.52, 6.28, and 6.31 kWh/m2/day, respectively, and 6.30kWh/m2/day for East Gojjam Zone, which is actually a very good solar energy potential. According to the monthly average global horizontal solar radiation profiles, the study sites receive the highest solar radiation in April and lowest solar radiation in July and August. The radiation in Debre Markos varies between 3.97 and 5.88kWh/m2/day, but Debrewerk receives more uniform solar radiation throughout the year. By considering intermittency and average solar energy potential of the four sites, Debrewerq and Debre Markos are the best and the worst sites, respectively, for large solar energy projects.
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