Renewable Energy Resources and Technologies
Babak Keyvani; Bahador Fani; Hamed Karimi; Majid Moazzami; Ghazanfar Shahgholian
Abstract
Conventional droop control method has been widely adopted for power sharing between Distributed Generators (DGs) in microgrids. However, the mismatched feeder impedance of the Voltage-Sourced Inverters (VSI) may generate reactive power sharing error during islanding operation of a microgrid. In this ...
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Conventional droop control method has been widely adopted for power sharing between Distributed Generators (DGs) in microgrids. However, the mismatched feeder impedance of the Voltage-Sourced Inverters (VSI) may generate reactive power sharing error during islanding operation of a microgrid. In this paper, an improved droop control method is suggested to improve the reactive power sharing accuracy. In the proposed method, the slope correction of the droop characteristics is performed in such a way that the reactive power sharing error is reduced. In this method, the errors of reactive power sharing are detected by applying a clear signal to the microgrids and, then, by adding a new term to the P-ω and correcting the slope of Q-E, the reactive power sharing is done. In this way, the proposed method can successfully improve the reactive power sharing accuracy even at different X/R ratios. Another feature of this method is its high operation speed compared to the other methods of droop feature correction. The simulation results for a prototype microgrid point to the efficiency and flexibility of the proposed method.
Renewable Energy Resources and Technologies
Mohammad Reza Shekari; Seyed Mohammad Sadeghzadeh; Mahdi Golriz
Abstract
In recent decade, Perovskite Solar Cells (PSCs) have received considerable attention compared to other photovoltaic technologies. Despite the improvement of Power Conversion Efficiency (PCE) of PSCs, the chemical instability problem is still a matter of challenge. In this study, we have fabricated two ...
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In recent decade, Perovskite Solar Cells (PSCs) have received considerable attention compared to other photovoltaic technologies. Despite the improvement of Power Conversion Efficiency (PCE) of PSCs, the chemical instability problem is still a matter of challenge. In this study, we have fabricated two kinds of PSCs based on gold and carbon electrodes with the optimal PCE of about 15 % and 10.2 %, respectively. We prepared a novel carbon electrode using carbon black nanopowder and natural graphite flaky powder for Hole Transport Material (HTM) free carbon-based PSC (C-PSC). Current density-voltage characteristics over time were measured to compare the stability of devices. Scanning Electron Microscope (SEM) and Energy-dispersive X-ray Spectroscopy (EDS) analyses were carried out to study applied materials, layer, and surface structures of the cells. The crystal structure of perovskite and its association with the stability of PSCs were analyzed using an obtained X-ray diffraction (XRD) pattern. As a result, the constructed HTM-free C-PSC demonstrated high stability against air, retaining up to 90 % of its optimal efficiency after 2000 h in the dark under ambient conditions (relative humidity of (50 ± 5); average room temperature of 25 °C) in comparison to constructed gold-based PSCs (Gold-PSC) which are not stable at times. The experimental results show that novel low-cost and low-temperature carbon electrode could represent a wider prospect of reaching better stability for PSCs in the future.
Renewable Energy Resources and Technologies
Fariba Heidarpour; Ghazanfar shahgholian
Abstract
The sustainability of hydraulic turbines was one of the most important issues considered by electrical energy provider experts. Increased electromechanical oscillation damping is one of the key issues in the turbines sustainability. Electromechanical oscillations, if not quickly damp, can threaten the ...
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The sustainability of hydraulic turbines was one of the most important issues considered by electrical energy provider experts. Increased electromechanical oscillation damping is one of the key issues in the turbines sustainability. Electromechanical oscillations, if not quickly damp, can threaten the stability of hydraulic turbines and causes the separation of different parts of the network form each other, specifically ejecting the generators from the turbine. In this paper, a Round-robin scheduling algorithm was used based on a neural network and simulations were investigated by several methods. Thus, using the designed Round-robin scheduling algorithm, we can find three parameters simultaneously. So optimal outputs can determine by these three parameters, which would be investigated as the optimal output range. In other words, besides using other algorithms capability, it can eliminate some of their disadvantages. The Round-robin scheduling algorithm is more suitable for large and extensive systems, due to reducing the number input variables and have a non-linear and resistant structure at the same time, This algorithm can actually use for optimizing any other controlling methods.