Ludmil Stoyanov - Academia.edu (original) (raw)

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Papers by Ludmil Stoyanov

Solar Energy, 2017

A simulation tool for the operation of a hybrid PV/Wind plant coupled with a hydro-pumping storag... more A simulation tool for the operation of a hybrid PV/Wind plant coupled with a hydro-pumping storage (HPS) was built; it was used for simulating the behavior of such a system among an energy mix constituted by fuel oil generators and electrical cables in an insular electrical network. Each subsystem is modeled with a variable efficiency depending on the operating regime and on solar and wind sources variability. An optimization of the hydro-pumping system operation was developed using four reversible pumps in parallel. The objective is to shave the electrical peak demand in replacement of costly and polluting combustible turbines. An energy situation like the one in Corsica Island is considered and all the electrical productions are taken into account, not only renewables but also fuel and imported electrical energy. The covered part of the peak demand can reach 80% in an annual basis and the influence of the hybrid system characteristics on the performances were studied. Some hybrid systems configurations were highlighted.

ABSTRACT The modeling and simulation of the electrical machines increases its importance. This pa... more ABSTRACT The modeling and simulation of the electrical machines increases its importance. This paper shows the modeling of squirrel cage induction machine in Matlab/Simulink and the use of the model for simulation of the machine performance characteristics and transient processes for educational purposes. The realized model allows the introduction of the students both in the machine modeling and in the laboratory works in the laboratory “Electrical machines I” of the Department of Electrical machines in the Faculty of Electrical Engineering of the Technical University of Sofia.

2021 17th Conference on Electrical Machines, Drives and Power Systems (ELMA), Jul 1, 2021

This paper presents the creation of a set with appropriate web applications, using Matlab Web App... more This paper presents the creation of a set with appropriate web applications, using Matlab Web Apps. The set’s aim is to ease the teaching process in distance learning for Engineering specialties in Electrical engineering. This set represents an adaptation of the existing test benches in the laboratory exercises of the discipline Electrical Machines part II, especially for the synchronous machines. The developed web applications propose a user-friendly and realistic user interface. The machines are modeled following the generalized theory of the electrical machines in the Matlab environment. The models are then transformed in web applications. The presented simulation and experimental results show good correspondence, which justify the applications’ accuracy.

The main goal of this work is to develop and validate a mathematical model of an experimental tes... more The main goal of this work is to develop and validate a mathematical model of an experimental test bench used for laboratory works on the discipline ‘’Electrical machines part 2". This model will be presented to the students during their distance learning, imposed by the COVID-19 pandemic. The test bench in mind is used to consider the process of connecting a synchronous generator to the electrical grid. The generator’s parameters are measured and applied to a model of the machine in the Matlab/Simulink environment. The simulation results are compared with the experimental ones and show good correspondence, validating the proposed model.

The fuel cells technology improvement facilitates its application in different fields of human li... more The fuel cells technology improvement facilitates its application in different fields of human life. Thus the modeling and simulation of the fuel cells operation become more and more important not only for their manufacturers but also for the researchers in their application fields. This paper presents the dynamic modeling of a proton exchange membrane fuel cell with its control system for the aims of electric hybrid systems simulation. The realized model in Matlab-Simulink takes into account the processes in the fuel cell when its current varies. The control system ensures the accomplishment of the system operator requirement for the fuel cell output power.

2021 17th Conference on Electrical Machines, Drives and Power Systems (ELMA), Jul 1, 2021

The paper deals with modeling of stand-alone hybrid system, which uses photovoltaic installation ... more The paper deals with modeling of stand-alone hybrid system, which uses photovoltaic installation and fuel cell stack for generation and electrolyzer with hydrogen tank for storage. The components of the system are modeled with appropriate mathematical equations, describing the specific phenomena for each element, and implemented in Matlab Simulink environment. Simulation results are presented for 9 days, using meteorological data from experimental set-up in Ajaccio, France. The results show a good functionality of the system and confirm the possibility to use it for satisfaction of stand-alone consumer.

HAL (Le Centre pour la Communication Scientifique Directe), Jun 1, 2017

HAL (Le Centre pour la Communication Scientifique Directe), 2017

HAL (Le Centre pour la Communication Scientifique Directe), Apr 23, 2014

L'intégration des systèmes photovoltaïques (PV) dans les bâtiments augmente. La productiv... more L'intégration des systèmes photovoltaïques (PV) dans les bâtiments augmente. La productivité de ces systèmes dépend de l'orientation et de la forme du bâtiment – les façades et les toits, de la technologie des modules photovoltaïques et la latitude de l'installation. La quantité d'énergie produite est souvent loin de l'optimum pour la situation géographique donnée. Cela engendre des disputes sur la rationalité des investissements pour l'intégration des systèmes PV dans les bâtiments. Ainsi, on défend le principe d'intégration en soulignant le fait que le bâtiment produit de l'énergie même si sa production n'est pas optimale. Cet argument serrait renforcé si les prix des modules photovoltaïques baissaient. Il est intéressant de déterminer la productivité des systèmes intégrés dès l'étape de conception des bâtiments. De cette façon il est possible de donner des prescriptions aux architectes et aux ingénieurs en génie civil pour l'orientation, la hauteur et la forme du bâtiment ainsi que pour les surfaces avec modules PV. Dans cet article, nous montrons différentes possibilités pour l'intégration des systèmes photovoltaïques de différentes technologies dans des bâtiments avec différentes formes, orientation et latitude dans l'Hémisphère Nord. Pour déterminer l'énergie produite par les modules, nous utiliserons le modèle de Durisch qui tient compte de l'influence de l'irradiation solaire et de la température ambiante sur le rendement des modules photovoltaïques pour quatre technologies – silicium monocristallin, polycristallin et amorphe et modules à couche mince. Mots clés: Modules photovoltaïques intégrés, conversion de l'irradiation horizontale, modélisation de modules photovoltaïques de différentes technologies, estimation de la production.

HAL (Le Centre pour la Communication Scientifique Directe), Nov 11, 2015

HAL (Le Centre pour la Communication Scientifique Directe), Sep 30, 2018

2022 8th International Conference on Energy Efficiency and Agricultural Engineering (EE&AE)

2019 11th Electrical Engineering Faculty Conference (BulEF), 2019

The paper presents the comparison of different approaches for forecasting of the solar radiation ... more The paper presents the comparison of different approaches for forecasting of the solar radiation using artificial neural networks (ANN). The estimation of the energy yield of photovoltaic installation is very important for the electrical grid stability. This estimation is only possible if a good solar radiation forecast is available. Different approaches for this forecasting are possible. One of the most used statistical method is the artificial neural network. The main drawback of this method is the need of large amount of collected data for the network learning. The authors' team dispose with large database to avoid this disadvantage. Three approaches for the solar radiation forecasting are considered. The difference is in the input variables. The first approach uses information for the solar radiation for 6 days before the forecasted one. The others two approaches use historical data for the forecasted day - respectively 2 and 4 years before this day. For each approach two different topologies are considered - with one and two hidden layers. The number of neurons in the layers varies. The results show the advantages and the drawbacks of each approach in function of the topology. However, all three approaches are more or less appropriate for the solar radiation forecasting.

An optimal sizing methodology based on an energy approach is described and applied to gridconnect... more An optimal sizing methodology based on an energy approach is described and applied to gridconnected photovoltaic systems taking into account the photovoltaic module technology and inclination, the inverter type and the location. A model describing the efficiency for mSi, pSi, aSi and CIS is used. The method has been applied on various meteorological stations in Bulgaria. The main parameter affecting the sizing is the inverter efficiency curve. The influence of the PV module technology seems less important excepted for amorphous photovoltaic modules for which special remarks have been made. The inclination on the PV system influences the performances particularly when the inverter is undersized compared to the PV peak power.