Faculty of Electrical Engineering and Information Technologies

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    Cuckoo Search Algorithm Applied for Maximum Power Point Determination of Bifacial PV Using Different PV Cell Models
    (AEDERMACP (European Association for the Development of Renewable Energies and Power Quality), 2025-07)
    Najdoska, A.
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    Cvetkovski, G.
    This paper proposes an application of a novel nature-inspired algorithm called Cuckoo Search Algorithm (CSA) in the de termination of the maximum power point in a bifacial photovoltaic (PV). The optimisation algorithm mimics the behaviour of the cuckoo birds, especially their very strange reproduction strategy. The Cuckoo Search in general is a minimisation search algorithm and suits fine with the objective function of this investigation, which is the absolute value of the power difference of the calculated and catalogue value for given metrological conditions. For the calculated output power three different photovoltaic cell presentations are used: ideal single, real single-diode and double-diode PV cell presentation. The determination of the maximum power point is performed using the different photovoltaic cell circuits and for different solar irradiation at constant temperature. The aim of this work is to compare the results gained using the three PV cell models using the cuckoo search optimisation algorithm.
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    Maximum Power Point Determination of Bifacial PV Using Multi-Verse Optimization Algorithm Applied on Different Cell Models
    (Walter de Gruyter GmbH, 2025-01-01)
    Najdoska, Angela
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    In the design process of a photovoltaic (PV) power plant, determination of the maximum power that can be extracted from the PV modules is essential, especially for the dimensioning of the individual parts of the plant. This paper presents the determination of the maximum power point (MPPT) of a bifacial PV system using three different cell models. The optimal power point is determined by using a novel multi-verse optimization (MVO) algorithm as the optimization tool. In this research work the MPPT of bifacial PV modules is determined by using the following three PV cell models: ideal single diode model, real single diode model, and two-diode model of PV cell. These cell models are developed for single-sided PV modules and therefore a proper modification of the models is necessary in order to be applied for the investigated modules. The purpose of this optimization procedure is to determine the maximum power of a bifacial PV module by minimizing the power difference between the calculated power and the experimentally determined power for certain atmospheric conditions.
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    Bias in vital signs? Machine learning models can learn patients’ race or ethnicity from the values of vital signs alone
    (BMJ, 2025-07-10)
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    Mullan, Irene Dankwa
    Objectives To investigate whether machine learning (ML) algorithms can learn racial or ethnic information from the vital signs alone. Methods A retrospective cohort study of critically ill patients between 2014 and 2015 from the multicentre eICU-CRD critical care database involving 335 intensive care units in 208 US hospitals, containing 200 859 admissions. We extracted 10 763 critical care admissions of patients aged 18 and over, alive during the first 24 hours after admission, with recorded race or ethnicity as well as at least two measurements of heart rate, oxygen saturation, respiratory rate and blood pressure. Pairs of subgroups were matched based on age, gender, admission diagnosis and disease severity. XGBoost, Random Forest and Logistic Regression algorithms were used to predict recorded race or ethnicity based on the values of vital signs. Results Models derived from only four vital signs can predict patients’ recorded race or ethnicity with an area under the curve (AUC) of 0.74 (±0.030) between White and Black patients, AUC of 0.74 (±0.030) between Hispanic and Black patients and AUC of 0.67 (±0.072) between Hispanic and White patients, even when controlling for known factors. There were very small, but statistically significant differences between heart rate, oxygen saturation and blood pressure, but not respiration rate and invasively measured oxygen saturation. Discussion ML algorithms can extract racial or ethnicity information from vital signs alone across diverse patient populations, even when controlling for known biases such as pulse oximetry variations and comorbidities. The model correctly classified the race or ethnicity in two out of three patients, indicating that this outcome is not random. Conclusion Vital signs embed racial information that can be learnt by ML algorithms, posing a significant risk to equitable clinical decision-making. Mitigating measures might be challenging, considering the fundamental role of vital signs in clinical decision-making.
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    Optimization of Grid-Connected Microgrids with Residential Prosumers Using an Improved Genetic Algorithm
    (2024)
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    With the continuous increase of the microgrids’ implementation into the power system the problem of maintaining their stability and balance arises and the necessity to adopt an appropriate energy management system emerges. This paper analyses the optimization of the grid-connected microgrid, which consists of a photovoltaic generator, a wind generator, a battery, and residential prosumers. The paper presents the application of an improved genetic algorithm, which takes into consideration the voltage levels on the connection points of the generators and the prosumers, as well as the trading with the local grid. The proposed algorithm suggests the usage of the standard genetic algorithm with the improvement in the fitness and selection process. The results of the simulation are compared with the results obtained when using a standard genetic algorithm with five different types of selection.
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    Modified genetic algorithm for unit commitment of grid connected microgrids under real time pricing conditions
    (International Journal on Information Technologies and Security, 2024-09-01)
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    <jats:p>This paper introduces a modification of the genetic algorithm aimed at enhancing the selection process for reproducing the next generation. This modification accelerates the optimization process and improves the outcome. The case study analyzes a grid-connected microgrid comprising renewable energy sources, a battery storage system, prosumers with installed photovoltaic generators, and consumers. The effectiveness of the proposed modification is validated through comparison with two selection algorithms commonly used in the standard genetic algorithms.</jats:p>