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Effective damping of local low frequency oscillations in power systems integrated with bulk PV generation

Protection and Control of Modern Power Systems 2021年第1期6卷 512-524页

作者： ahmed hesham abd el-kar.em Mohamed abd elhameed Mahmoud M.elkholy Operation Engineer at New Capital Power Plant New Capital CityEgypt electrical Power and Machines Department Faculty of EngineeringZagazig UniversityZagazigEgypt

High penetration of renewable sources into conventional power systems results in reduction of system inertia and noticeable low-frequency oscillations (LFOs) in the rotor speed of synchronous generators. In this paper, we propose effective damping of LFOs by incorporating a supplementary damping controller with a photovoltaic (PV) generating station, where the parameters of this controller are coordinated optimally with those of a power system stabilizer (PSS). The proposed method is applied to damp local electromechanical modes by studying a system comprising a synchronous generator and a PV station connected to an infinite bus. The PV station is modeled following the instructions of the Western electricity Coordinating Council. The problem is modeled as an optimization problem, where the damping ratio of the electromechanical modes is designed as the objective function. Constraints including upper and lower limits of decision parameters and damping ratio of other modes are considered by imposing penalties on the objective function. Different optimization algorithms are used to pursue the optimal design, such as political, improved gray wolves and equilibrium optimizers. The results validate the effectiveness of the proposed controller with PSS in damping local modes of oscillations.

关键词： Low frequency oscillations Damping controller PV WECC

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electrowinning of Copper Using Rotating Cylinder electrode Utilizing Lead Anode

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Engineering（科研） 2011年第4期3卷 340-358页

作者： hesham Soliman ahmed abd el-Moneim 不详

The effect of lead anode, rotating cylinder electrode (RCE), amount of 1,2-dihydroxypropane (12-DHP), temperature and rotation on the electrowinning of copper from low concentration acidified copper sulphate solution has been investigated. Copper powder was electrodeposited onto RCE that made of pure copper. From cyclic voltammetry experiments, an empirical parameter called the departure percent, S, was obtained which may represent the stability of the organic additive in the given medium and under the experimental conditions. The inhibition percentage, P, was 0.00 - 89.91% depending on the experimental variables. P was affected by temperature and mole fraction of 12-DHP, while rotation did not show any influence on it. Values of activation energy of electrodeposition process, Ea, were found to be less than 28 kJ mol-1 indicating diffusion controlled process. The overall mass transfer correlations under the present conditions have been computed using the dimensional analysis method. The data were valid for 90 emperature and the speed of rotation on the morphological changes of the electrodeposited copper powder as well as deposits composition and crystallite size have been studied. Various crystallite sizes ranged 7.1 nm - 250.6 nm were obtained and characterized by EDS and XRD. Different topographs proved that the rate of copper electrodeposition increased by increasing deposition time, temperature and the speed of rotation. Also, they proved that the deposition rate decreased by adding 12-DHP to the solution. Therefore, the results obtained by Sem supported those achieved by measuring the limiting current density and follow the normal manner when organic solvents were added to the electrodeposition bath.

关键词： electrodeposition electrowinning Lead Anode Rotating Cylinder electrode (RCE) 1 2-Dihydroxypropane (12-DHP) Copper Powder

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Moderate Secondary Tricuspid Regurgitation: Does It Worth More Time to Conserve?

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Open Journal of Thoracic Surgery 2021年第3期11卷 59-68页

作者： Montaser elsawy abd elaziz ahmed Labib Dokhan Awny Gamal Shalaby hesham Hassan ahmed Mohammed ahmed el-Hag-Aly Mohammed Fawzy eltaweel Cardithoracic Surgery Department Faculty of Medicine Menoufia University Menoufia Egypt Faculty of Medicine Jazan University Jazan KSA Cardiology Department Faculty of Medicine Menoufia University Menoufia Egypt

Background: Concomitant repair of moderate secondary tricuspid regurgitation (STR) during mitral valve surgery is still subject of controverse. This research aims to study the early and mid-term postoperative influence of tricuspid repair on the clinical outcomes and right ventricular functions. Methods: This is a retrospective cohort study of 92 patients with moderate STR who underwent tricuspid valve repair

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Moderate Secondary Tricuspid Regurgitation: Does It Worth More Time to Conserve?

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Open Journal of Thoracic Surgery（胸外科期刊） 2021年第3期

作者： Montaser elsawy abd elaziz ahmed Labib Dokhan Awny Gamal Shalaby hesham Hassan ahmed Mohammed ahmed el-Hag-Aly Mohammed Fawzy eltaweel

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