Zahari Zarkov

Zahari Zarkov
Technical University of Sofia | TU · Department of Electrical Machines

Doctor, PhD

About

58
Publications
103,148
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234
Citations
Introduction
Zahari Zarkov currently works at the Department of Electrical Machines, Technical University of Sofia. Zahari does research in Power electronic converters for Renewable energy sources, Electricity production systems from RES; Control of electrical generators; Photovoltaic systems; Hybrid systems with RES; Electrical Engineering. Their current project is 'University Research Complex.'
Additional affiliations
May 2007 - present
Technical University of Sofia
Position
  • Professor (Associate)
Education
January 1992 - May 1995
Technical University of Sofia
Field of study
  • Electrical Engineering, Control of step motors
October 1983 - June 1990
Technical University of Sofia
Field of study
  • Electronics

Publications

Publications (58)
Conference Paper
Full-text available
The paper deals with the modeling and comparison of the performance of photovoltaic (PV) generators with panels from different technologies. The generators are part of an experimental platform at the Technical University of Sofia and operate in real weather conditions. The modeling of the PV modules is based on the Durisch's model using two approac...
Conference Paper
Full-text available
This paper presents the results of the modeling and comparison of parallel structures of DC-DC converters for application in wind energy conversion systems with low power. Three different topologies with boost capabilities are studied: boost, non-inverting buck-boost and SEPIC converter. The simulation models are created using a Matlab/Simscape env...
Article
Full-text available
The Green Deal and increased nutritional needs are driving factors in human activities nowadays. Agriculture is an essential economic sector that can profit from the application of renewable energy sources by the assimilation of off-grid, arid and barren terrains. Power supplied by hybrid systems for water pumping is a solution for overcoming the s...
Chapter
The penetration of building-integrated photovoltaic (BIPV) systems increases due to ecological and aesthetic factors. The productivity of the PV systems depends on the orientation, the angle of inclination, the technology of the modules, and the latitude of the installation. Thus, the amount of the produced energy relates on the shape of the buildi...
Article
Full-text available
Photovoltaic (PV) energy has become competitive in power generation as an alternative to fossil fuels over the past decades. The installation of solar energy systems is expected to increase rapidly with the further development of the power electronics technology. This paper presents the development and modelling of a DC-DC converter for connection...
Article
Full-text available
The purpose of this work is to assess the energies produced by a hybrid system composed of photovoltaic generators and wind turbines. This study aims to develop a method, which could facilitate the sizing of photovoltaic and wind generators in a given hybrid system. The proposed method could also help with the sizing of storage devices in the hybri...
Article
Full-text available
The purpose of the work is to study and compare the performance of photovoltaic (PV) generators built with different types of panels and operating in real weather conditions. The paper reports the results from an experimental and theoretical study of systems with PV modules manufactured according to different technologies and using different materi...
Article
Full-text available
This paper deals with the combined influence of photovoltaic and different wind energy potentials and respectively the produced energy on the operation of an autonomous hybrid system. The studied system comprises a PV generator, a wind generator and three micro gas turbines (MGT) supplying power to residential loads. The installed power of the PV a...
Conference Paper
Full-text available
The paper presents the development of a simulation model of a wind turbine (WT) emulator. The emulator consists of a DC motor, electronic converter and controller. The mathematical modelling of a wind turbine and separately excited DC motor with electronic converter is performed in Matlab/Simulink environment. The WT performance characteristics are...
Article
Full-text available
This paper compares thin film photovoltaic technologies’ productivity for different installation sites and surface positions. The aim is to guide architects to increase the energy yield during the design of buildings with integrated photovoltaic panels by providing information on the appropriate inclination and orientation of the panels. Meteorolog...
Conference Paper
Full-text available
In this work the authors studied a wind generator system consisting in: three-phase synchronous generator, rectifier, voltage limiter and single-phase inverter connected to the grid. A simulation model of the electrical part of the wind generator was created in the environment of PSpice. An electronic circuit of voltage limiter with hysteresis cont...
Article
Full-text available
The current paper presents the modeling of photovoltaic module for Maxi-mum power point tracking (MPPT) purposes. First the model theory is described and the experimental determination of the model constants is presented. Finally the MPPT strategy is explained and illustrated.
Article
Full-text available
This paper presents a control strategy to limit the output power of photo-voltaic array. Two possibilities are discussed with their realization using lookup tables and fuzzy logic. Finally are shown simulation results from the system model, realized in Matlab/Simulink.
Article
Full-text available
This paper presents analysis of a grid-connected PV system with Maximum Power Point Tracking (MPPT) control. A detailed simulation model of single-phase and a three-phase system with MPPT control is created. Two MPPT methods are studied, a fuzzy logic-based and a model-based MPPT using lookup tables. Simula-tions are performed to test the controlle...
Article
Full-text available
This paper presents three control strategies for grid-connected photovoltaic (PV) systems – maximum power point tracking, constant power point tracking and limited power point tracking. The first one is widely used while the latter two are proposed by the authors to fulfil system operator re-quirements. In some cases, when there is an excess of gen...
Conference Paper
Full-text available
The paper presents the modelling of a wind energy conversion system with doubly fed induction generator with control systems operating in two modes – maximum and limited power point tracking. The simulation results illustrate the system’s correct operation.
Conference Paper
Full-text available
This paper presents a study on the influence of the mechanical inertia on the maximum power point tracking (MPPT) control of a wind turbine with a doubly fed induction generator. The models of system elements are presented and the control systems functions are described. The realized Matlab model is validated with experimental bench with a dSPACE m...
Article
Full-text available
This article examines the problems of integration of renewable energies in power systems, resulting from the changing nature of primary sources. Possible solutions to overcome the problem are the development of hybrid systems and/or the introduction of devices for energy storage. These devices serve to compensate for the change of power from renewa...
Article
Full-text available
This paper presents an experimental study of the losses doubly-fed induction generator (DFIG) for wind energy conversion system. The experiments were performed on a laboratory test bench. The losses in the components of the system -electronic converters, transformer and induction machine -are determined by measuring the power in different system po...
Conference Paper
Full-text available
The paper investigates the performance of variable speed wind turbine (VSWT) configuration with DC-DC converter under restricted output power conditions. The considered regimes of turbine operation are: at maximum available aerodynamic power and at limited output electric power. The wind turbine system consist of synchronous generator (SG) connecte...
Article
Full-text available
The paper deals with the modeling and study of power flows in doubly fed induction generator (DFIG). The power flows directions are presented in different rotor speed conditions and the system components models are illustrated. The models are realized in the Matlab/Simulink environment and some numeric results are presented to justify the model cor...
Article
Full-text available
The paper studies the performance of variable speed wind turbine (VSWT) configuration with DC-DC converter under restricted output power condition. The wind turbine system consists of permanent magnet synchronous generator (PMSG), diode rectifier, boost converter and load. New control strategy, based on the maximum power point tracking (MPPT) and l...
Article
Full-text available
This paper presents the applications of supercapacitor energy storage in hybrid systems with renewable energy sources, as well as with other energy storage technologies. Supercapacitors are capable to compensate the power variations of renewable energy sources due to the stochastic nature of the primary resources. These applications can be used in...
Conference Paper
Full-text available
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=5606570
Conference Paper
Full-text available
The paper studies the performance of variable speed wind turbine (VSWT) configuration with non-inverting buck-boost converter. The wind turbine systems consist of permanent magnet synchronous generator (PMSG) connected to diode rectifier, DC chopper and load. New control strategy, based on the maximum power point tracking (MPPT) and limited power p...
Article
Full-text available
The paper studies the performance of variable speed wind turbine (VSWT) configuration with non-inverting buck-boost converter. The wind turbine systems consist of permanent magnet synchronous generator (PMSG) connected to diode rectifier, DC chopper and load. New control strategy, based on the maximum power point tracking (MPPT) and limited power p...
Article
Full-text available
This paper is devoted to the study of a single-phase inverter for connection of generator using renewable energy sources (RES) to the utility grid. A computer model of the inverter is developed. The model allows inverter operation with variable in the time input power. Thus the inverter can be easily connected to a DC-DC converter with maximum powe...
Article
Full-text available
Taking in account the non-constant character of the primary sources in a hybrid system of renewable energy sources and the consumers that it is powering (some of them need a constant power source) the need of a power management in a hybrid system emerges. In this article we will review the researches in the domain of hybrid systems. Also we will di...
Conference Paper
Full-text available
La modélisation des convertisseurs statiques peut être assez compliquée pour des non spécialistes dans le domaine de l'électronique de puissance qui ont besoin de modéliser et simuler de systèmes complexes. Deux techniques simples et précises pour la modélisation d'un hacheur parallèle (convertisseur type Boost) et d'un convertisseur type Buck/Boos...
Article
Full-text available
The present paper investigates the system behavior of a rectifier and a DC-boost converter used in a wind generator with variable speed. In many cases a combination of diode rectifier and a DC boost converter is used as interface between the generator and the inverter in order to match the requirements for the DC bus voltage. Different models of th...
Article
Full-text available
In the recent years large employment and development of renewable energy sources has become noticeable. Energy converters and power limited energy networks mutual operation modeling and investigation are questions of present scientific interest. Renewable energ1es have stochastic nature and the produced power is variable. Thus, the power flow contr...
Conference Paper
Full-text available
The paper deals with the sizing and optimization of the hybrid systems with renewable energy sources. The classification according to different criteria has been made. The examples of optimization linked with different case studies are shown. Flexible hybrid system of renewable energy sources for validation of the optimization procedures and result...
Conference Paper
Full-text available
On examine les différents types de sources d'énergie renouvelables (SER) ou l'accent est mis sur la partie électrique et la connexion avec le réseau. Le caractère variable des ressources d'énergie primaire – l'énergie du vent, l'énergie solaire etc. impose souvent l'utilisation des dispositifs électroniques de puissance. On montre quelques possibil...
Conference Paper
Full-text available
The article deals with the state of the art of a hybrid power systems with renewable energy sources (HSRES). These systems are classified according to different criteria. It has been made a short review of the current state of their design, modelling, simulation and optimisation. The respective analysis has been made also. In conclusion, it has bee...

Questions

Questions (2)
Question
What is so called "C paste" used in the production process of CdTe photovoltaic cells?

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